International Journal of Fishes and Aquatic Sciences 1(1): 16-34, 2012
ISSN: 2049-8411; e-ISSN: 2049-842X
© Maxwell Scientific Organization, 2012
Submitted: April 17, 2012
Accepted: May 14, 2012
Published: July 25, 2012
Some Predatory Fishes, Birds, Mammals and Some Other Animals
in Culture Fisheries Management
E.N. Ogamba and J.F.N. Abowei
Department of Biological Sciences, Faculty of Science, Niger Delta University,
Wilberforce Island, Nigeria
Abstract: Some predatory fishes, birds, mammals and some other animals in culture fisheries management was
reviewed to enlighten fish culturist some expected challenges in culture fish fisheries management and practices.
Predatory fish, aquatic birds, aquatic mammals and some other animals (toads, coelenterates and crustaceans) create
some challenges to culture fisheries in Nigeria. These pests of fish destroy fish or hinder the production of target fish
species. Man also pouches on fishponds. However some pests to culture fisheries are also useful in culture fisheries
management and practices. These challenges and their management and discussed in this study to facilitate the
effective management of culture fisheries in Nigeria.
Keywords: Birds, culture fisheries, mammals and some other animals, Predatory fish, Some challenges
Sea anemones are poisonous to fish. Their tentacles can
also trap small fish.
The less familiar microscopic crustaceans such as
krill serve a vital link in the aquatic food chain. Billions
of these microscopic organisms swarm the lakes, seas
and ocean and form the main food for fish. However, in
brackish water crabs of the genus seasarma and
cardisoma are known to dig holes on pond dykes
causing leakages and seepages. The leakages
sometimes result in loss of fish and water from the
pond. Cirripedia (barnacles) grow on any hard substrate
like boards, sluice gate wall, monks’ wall and sluice
grooves. Planktonic crustacean such as copepods,
cladocerans and heparticoids are also dangerous pests.
If allowed to enter the water supply to the incubating
tanks, they can destroy fish eggs. They also compete for
oxygen in the incubator or hatching tanks.
In brackish waters, Crassostea gasar (oysters)
grow on pond grooves and can close the pond screens.
In fresh water, the bivalve, Etheria, can cause pond
screen closure. Neritina, Thias callifera and
Tympanotumus fuscatus occur in brackish water pond
bottom, competing for food and space with fish
(Runnegar, 1983; Ponder and Lindberg, 2008). Excess
of these molluscs disturb the pond ecological system
because they can cover the pond bottom and prevent the
pond mud from releasing nutrient. A review some
predatory fishes, birds, mammals and some other
animals in culture fisheries management enlightens fish
culturist creates awareness some challenges faced in
INTRODUCTION
Culture fisheries, like every other agriculture
practice encounter problems. Pests of fish are unwanted
animals or plants that destroy fish or hinder the
production of target fish species (NDES, 1997). These
pests can be grouped in to plants and animals. Any
unwanted living thing that can feel and move which
retards fish production is animal pest to fish. These may
be Predatory fish, Birds, mammals and some other. Fish
prey on fish. Predatory fishes prey directly on culture
fish and compete for food with the culture fish. Despite
their nuisance in culture fisheries, fish predators are
used in controlling fish over population in ponds.
However, fish culturist need be careful on the number
of predators, the size of prey and predator before
stocking. Water provides a critical habitat to a wide
variety of bird species (Oates et al., 2004). Many birds
feed on fish and can poach on fish in the pond.
Aquatic and semi-aquatic mammals are a diverse
group of mammals that dwell partly or entirely in
bodies of water (Margulis and Karlene, 1997). Man also
pouches on fishponds. Tadpoles feed on aquatic plants
and animals. Frogs live on fish fry and are therefore
harmful. They lay eggs on the surface of ponds. Large
masses of eggs consume much pond oxygen. This can
retard fish growth if not checked. The sea anemones
can grow on boards, sluice gates and grooves and on
concrete dykes in high salinity brackish water areas.
Corresponding Author: J.F.N. Jasper, Department of Biological Sciences, Faculty of Science, Niger Delta University,
Wilberforce Island, Nigeria
16
Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
Plate 6: Lateral view of Mugil cephalus
culture fish fisheries management and practices The
management of the pest is essential for the sustenance
of culture fisheries in Nigeria.
Plate 1: Lateral view of clarias gariepinus
PREDATORY FISHES
Fish predators are also useful in fish culture.
Predatory fishes are used in controlling fish over
population in ponds. For instance, one or two
sphyraena sp can be introduced into the pond to check
the number of Tilapia. Sphyraera species are
carnivorous and can reduce the number of Tilapia fish
in the pond. Be careful not to introduce much of such
predators. Megalops can also control the population of
Tilapia in the pond. Clarias sp and Heterobranchus are
good predators, which reduce Tilapia population.
Medium sizes of Clarias gariepinus (Plate 1) and
Heterobranchus
bidorsalis
or
Heterobranchus
longifiles (Plate 2) can be introduced into the pond
when the rate of reproduction of the Tilapia is excess.
These predators can attract and feed on the Tilapia fry.
Heterotis niloticus (Plate 3) feeds on Tilapia fry in fresh
water ponds and is therefore a useful predator.
However, fish culturist need be careful on the number
of predators, the size of prey and predator before
stocking.
Many predatory fish species exist: Clarias
gariepinus, Hemichromis faciatus, Cicllia collars,
Gymanarchus niloticus, Ophicephalus obscurus,
Protonas ennectus, Tettradon fahacca, Phenophthalmus
papilleo, Eleotris and Lutjamus goreensis. Others are
Chrysichitys nigrodigitatus (Plate 4), Lates niloticus
(Plate 5), Mugil cephalus (Plate 6), Epinephellus,
Spyraena barracuda, Elops lacerta and Megalops.
Predatory fishes prey directly on culture fish and
compete for food with the culture fish.
Plate 2: Dorsal view of Heterobranchus sp.: (http://upload.
wikimedia.org/Wikimedia/commons/2/2acatfishstubby-malanochromis.jpg)
Plate 3: Lateral views of two Heterotis niloticus during
courtship
Plate 4: Lateral view of Chrysichthys nigrodigitatus
Birds: Aquatic environments provide critical habitat to
a wide variety of bird species. Some aquatic birds
divide their time between aquatic and terrestrial
environments, while others spend most of their lives in
water, returning to land only to breed. Many familiar
bird groups are aquatic, including gulls and penguins as
well as recreationally important species such as ducks
Plate 5: Lateral view of the head region of Lates niloticus:
(http//en.wikipedia.org/wiki/file:Lates niloticu)
17 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
18 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
19 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
61
62
63
64
65
66
67
68
69
70
Plate 7: (1) Aechmophorus clarkii (Clark's Grebe), (2) Podiceps nigricollis (Eared Grebe), (3) Podilymbus podiceps (Pied-billed
Grebe), (4) Aechmophorus occidentalis (Western Grebe), (5) Pelecanus erythrorhynchos (American White Pelican),
(6) Phalacrocorax auritus (Double-crested Cormorant), (7) Nycticorax nycticorax (Black-crowned Night Heron), (8)
Bubulcus ibis (Cattle Egret), (9) Casmerodius albus (Great Egret), (10) Ardea herodias(Great Blue Heron), (11)
Egretta thula (Snowy Egret), (12) Plegadis chihi (White-faced Ibis), (13) Anas crecca (Green-winged Teal), (14) Anas
americana (American Wigeon), (15) Bucephala islandica (Barrow's Goldeneye), (16) Bucephala albeola
(Bufflehead), (17) Anas discors (Blue-winged Teal), (18) Branta canadensis (Canada Goose), (19) Aythya valisineria
(Canvasback), (20) Anas cyanoptera (Cinnamon Teal), (21) Bucephala clangula (Common Goldeneye), (22) Mergus
merganser (Common Merganser), (23) Anas strepera (Gadwall), (24) Aythya marila(Greater scaup), (25) Aythya
affinis (Lesser Scaup), (26) Anas platyrhynchos (Mallard), (27) Anas acuta (Northern Pintail), (28) Anas clypeata
(Northern Shoveler), (29) Mergus serrator (Red-breasted Merganser), (30) Aythya americana (Redhead), (31) Aythya
collaris (Ring-necked Duck), (32) Oxyura jamaicensis (Ruddy Duck), (33) Chen caerulescens (Snow Goose), (34)
Cygnus columbianus (Tundra Swan), (35) Aix sponsa (Wood Duck), (36) Fulica americana (American Coot), (37)
Grus canadensis (Sandhill Crane), (38) Porzana carolina (Sora), (39) Rallus limicola (Virginia Rail),
(40)Recurvirostra americana (American Avocet), (41) Calidris bairdii (Baird's Sandpiper), (42) Pluvialis squatarola
(Black-bellied Plover), (43) Himantopus mexicanus (Black-necked Stilt), (44) Gallinago gallinago (Common Snipe),
(45) Tringa melanoleuca (Greater Yellowlegs), (46) Charadrius vociferus (Killdeer), (47) Numenius americanus
(Long-billed Curlew), (48) Limnodromus scolopaceus (Long-billed Dowitcher), (49) Calidris minutilla (Least
Sandpiper), (50) Tringa flavipes (Lesser Yellowlegs), (51) Limosa fedoa (Marbled Godwit), (52) Calidris canutu (Red
Knot), (53) Phalaropus lobatus (Red-necked Phalarope), (54) Calidris alba (Sanderling), (55) Charadrius
semipalmatus (Semipalmated Plover), (56) Calidrius pusilla (Semipalmated Sandpiper), (57) Charadrius alexandrinu
(Snowy Plover), (58) Actitis macularia (Spotted Sandpiper), (59) Calidris himantopus (Stilt Sandpiper), (60)
Numenius phaeopus (Western Sandpiper), (61) Catoptrophorus semipalmatus (Whimbrel), (62) Calidris mauri
(Willet), (63) Phalaropus tricolor (Wilson's Phalarope), (64) Chlidonias niger (Black Tern), (65) Larus philadelphia
(Bonaparte's Gull), (66) Larus californicus (California Gull), (67) Sterna caspia (Caspian Tern), (68) Sterna forsteri
(Forster's Tern), (69) Larus pipixcan (Franklin's Gull), (70) Larus delawarensis (Ring-billed Gull)
sandpipers and plovers. Diving birds describe a broad
group of species that occupy waters deeper than wading
species. These birds dive, plunge, or swim after fish
(NDES, 2003).
The American widgeon is a common marsh duck
which spends much of its time in deep water. It is
nicknamed "bald pate" because the male has a white
stripe on its head. Well-known diving birds include
ducks, geese, swans, pelicans and penguins. These
highly aquatic birds have evolved special adaptations to
their habitat, such as webbed feet for swimming and
and geese (Oates et al., 2004). Wading birds occupy
shallow-water habitats in both fresh-water and saltwater
environments. They have long, thin legs that allow
them to walk through water easily while keeping the
rest of their bodies dry. Some wading species find food
by stirring the water with their feet; others use their
beaks to filter food. Larger species with long legs and
great height also possess long flexible necks that allow
them to reach food below the water surface. Wellknown wading species include flamingos, cranes,
herons, storks and egrets. Smaller birds include
20 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
waterproof feathers. Salt-water species also possess
special salt glands that help excrete the excess salt that
results from drinking sea water. Diving birds associated
with marine habitats also are called seabirds. Many
seabirds spend large portions of time far from land and
all obtain food from the sea. However, all species return
to land to lay eggs. In some places, seabirds can occur
in staggering numbers-off the coast of Newfoundland,
for example, some 35 to 40 million seabirds are
documented yearly. Large breeding colonies of colorful
puffins, as well as murres, storm petrels and other
species attract numerous tourists in the spring. Penguins
are perhaps the most aquatic of all diving birds (NDES,
1997).
In some species, individuals return to land only to
breed and molt. Like marine mammals, penguins that
dive underwater must return to the water surface to
breathe. Many penguins feed on krill (a small, shrimplike crustacean), though some species hunt larger prey
such as squid and fish. Penguins possess a streamlined
body and are well-adapted to underwater swimming,
achieving speeds as great as 15 km (9 miles) per h. A
specialized fat layer and dense, waterproof feathers help
them maintain appropriate body temperatures in frigid
Antarctic waters. Penguin wings have been modified
through evolution to form paddle-like flippers.
Penguins are often described as "flying through water"
because their wing motions during swimming resemble
those of flying birds.
Many birds feed on fish and can poach on fish in
the pond (Plate 7). The commonest birds are Scopus
unbretta (Hammer head), Ardea goliath (Goliath
Heron), Ardea cinerea (Grey Heron), Egretta gazetta
(Liltle egret), Egretta alba (Great white egret), Halcyon
malimbucus (Blue breasted king-fisher), Alcedo athis
(King fisher) (IUCN, 1992). These birds have good
eyes, powerful wings, long beaks and fast movements.
Some can swim. These modifications enable them to
catch fish easily (Hayward and Ryland, 1995).
Plate 8: A baby amazonian manatee (Trichechus inunguis)
Plate 9: Amazon river dolphin (Inia geoffrensis)
various freshwater species, such as the Platypus and the
European Otter (GEMS, 1992).
Order Sirenia: Sirenians; family Trichechidae:
manatees (3 species, however, the West Indian manatee
lives in saltwater), Amazonian Manatee (Trichechus
inunguis) (Plate 8), African Manatee (Trichechus
senegalensis), Dwarf Manatee (Trichechus pygmaeus)
(validity questionable)
Order
Cetacea:
Cetaceans;
Super
family
Platanistoidea, Family Platanistidae; Ganges and Indus
River Dolphin, Platanista gangetica with two
subspecies, Ganges River Dolphin (or Susu),
Platanista gangetica gangetica, Indus River
Dolphin (or Bhulan), Platanista gangetica minor
Family Iniidae, Amazon River Dolphin (or Boto),
Inia geoffrensis (Plate 9); Family Lipotidae Chinese
River Dolphin (or Baiji), Lipotes vexillifer (functionally
extinct, since December 2006)
Family Pontoporiidae La Plata Dolphin (or
Franciscana), Pontoporia blainvillei
MAMMALS
Some mammals especially the Otters are known to
feed on fish (Happold, 1987). The common known
Otter is Lutrea maculicollis (NDES, 2003). There is
also another Otter, the Congo clawless Otter, Aonyx
congica. Man also pouches on fishponds. Aquatic and
semi-aquatic mammals are a diverse group of
mammals that dwell partly or
entirely in
bodies of water (IUCN, 1992). They include the various
marine mammals that dwell in oceans, as well as
Order Carnivora: family Mustelidae; Genus Lutra;
Eurasian otter (Lutra lutra) (Plate 10), Hairy-nosed
otter (Lutra sumatrana). Genus Hydrictis; Spottednecked otter (Hydrictis maculicollis). Genus Lutrogale ;
Smooth-coated otter (Lutrogale perspicillata). Genus
Lontra ; North Amerian River Otter (Lontra
canadensis) (Plate 11), Southern river otter (Lontra
21 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
Plate 10: Eurasian otter (Lutra lutra)
Plate
A
partially
submerged
hippopotamus
(Hippopotamusamphibius):
(http://en.
wikipedia.org/wiki/File:Hippo_memphinis.jpg)
provocax), Neotropical river otter (Lontra longicaudis).
Genus Pteronura ; Giant otter (Pteronura brasiliensis).
Genus Aonyx; African clawless otter (Aonyx capensis),
Oriental small-clawed otter (Aonyx cinerea), family
Phocidae. Genus Pusa; Baikal seal (Pusa sibirica),
Ladoga seal (Pusa hispida ladogensis), Saimaa seal
(Pusa hispida saimensis). Order Rodentia: Rodents;
Suborder Hystricomorpha; Capybara (Hydrochoerus
hydrochaeris) (Plate 12).
Plate 11: A north american river otter (Lontra canadensis):
(htt://en.wikipedia.org/wiki/File:RiverOttaSwimmin
gOregonZoo.jpg)
Family Castoridae: Beavers; American Beaver
(Castor canadensis) (Plate 13), European beaver
(Castor fiber); Family Cricetidae; Muskrat (Ondatra
zibethicus); Family Myocastoridae; Coypu (Myocastor
coypus); Family Cricetidae; European Water Vole
(Arvicola
amphibius).
Order
Monotremata:
Monotremes; Platypus (Ornithorhynchus anatinus)
(Plate 14).
Plate 12: Capybara (Hydrochoerus hydrochaeris): (http://en.
wikipedia.org/wiki/File:capybara_Hattiesburg_zooj
pg)
Order Artiodactyla: Even-toed ungulates; Family
Hippopotamidae: Hippopotamuses, Hippopotamus
(Hippopotamus amphibius) (Plate 15), Pygmy
hippopotamus (Choeropsis liberiensis)
Order Afrosoricida: Giant Otter Shrew (Potamogale
velox)
Order Soricomorpha: Russian Desman (Desmana
moschata)
Order
Didelphimorphia:
Opossums;
Family
Didelphidae: Opossums, Yapok (Chironectes
minimus)
Plate 13: A north american beaver (Castor canadensis): (http:
//en.wikipedia.org/wiki/File:Castor_canadensis.jpg)
Coelenterates: Coelenterata is an obsolete term
encompassing two animal phyla, the Ctenophora (comb
jellies) (Plate 16) and the Cnidaria (coral animals, true
jellies, sea anemones, sea pens and their allies). The
name comes from the Greek "koilos" ("full bellied"),
referring to the hollow body cavity common to these
two phyla. They have very simple tissue organization,
with only two layers of cells, external and internal. The
term coelenterate (pronounced as "silentarete") is no
longer recognized as scientifically valid, as the Cnidaria
Plate 14: A platypus (Ornithorhynchus anatinus): (http://en.
wikipedia.org/wiki/File:Platypus.jpg)
22 15:
Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
Plate 16: Coelenterata (http://en.wikipedia.org/wiki/File)
individual. Jellyfish have separate male and female
individuals. The sea anemones can grow on boards,
sluice gates and grooves and on concrete dykes in high
salinity brackish water areas. Sea anemones are
poisonous to fish. Their tentacles can also trap small
fish. Coelentratates can be controlled in the pond by
removing them manually (Hughes, 2003).
and Ctenophora are placed at equal rank under the
Metazoa with the other phyla of animals. Cnidaria
means "to sting". A single term encompassing these
two phyla but leaving out all others of equal rank would
be considered paraphyletic. Nonetheless, the term
coelenterate is still used in informal settings to refer to
the Cnidaria and Ctenophora. Complicating the issue is
the 1997 work of Lynn Margulis (revising an earlier
model by Thomas Cavalier-Smith) that placed the
Cnidaria and Ctenophora alone under the Radiata
branch of the Eumetazoa subregnum. (The latter refers
to all the animals except the sponges, Trichoplax and
the still poorly-understood Mesozoa.) Neither grouping
is accepted universally; however, both are commonly
encountered in taxonomic literature.
These are aquatic animals that include the hydra,
sea anemones, jelly fish and coral polyps. The coral
reefs of the tropical seas are the skeletal remains of
coral polyps that have accumulated over hundreds of
years. Coelenterates have specialized cells and tissues.
Their body is radially symmetrical. Most coelenterates
have two body forms in their life cycle
The stationary cylindrical hydroid polyp, usually
attached to rocks; and the free-swimming umbrellashapes medusa. In the jellyfish, the medusa form is
dominant. The hydra, sea anemones and coral polyps
only exist as the polyps. The medusa form is absent.
Some polyps’ forms such as the sea anemone and hydra
live single, while others like the coral polyps live in
colonies. The hydra has a sac like body with a single
opening and the mouth, through which food is taken in
and wastes are discharged. The body wall is made up of
two layers of cell with a gelatinous layer in between.
The mouth is surrounded by, tentacles that help to catch
food and push it into the gut. Tentacles have many
specialized stinging cells, which can sting the prey
(Barnes, 1982).
Coelenterates reproduce asexually by producing
outgrowth from their body walls known as buds.
Budding often occurs during the favorable season,
which food is plentiful. Coelenterates also reproduce
sexually by producing male and female gametes. In the
hydra, both the testis and ovary are found in the same
Crustaceans: Crustaceans (Crustacea) form a very
large group of arthropods, usually treated as a
subphylum, which includes such familiar animals as
crabs, lobsters (Limkpe, 1991), crayfish, shrimp, krill
and barnacles. The 67,000 described species range in
size from Stygotantulus stocki at 0.1 mm (0.004 in), to
the Japanese spider crab with a leg span of up to 12.5 ft
(3.8 m) and a mass of 44 lb (20 kg). Like other
arthropods, crustaceans have an exoskeleton, which
they moult to grow. They are distinguished from other
groups of arthropods, such as insects, myriapods and
chelicerates, by the possession of biramous (twoparted) limbs and by the nauplius form of the larvae.
Most crustaceans are free-living aquatic animals, but
some are terrestrial (e.g., woodlice), some are parasitic
(e.g., Rhizocephala, fish lice, tongue worms) and some
are sessile (e.g., barnacles). The group has an extensive
fossil record, reaching back to the Cambrian and
includes living fossils such as Triops cancriformis,
which has existed apparently unchanged since the
Triassic period. More than 10 million tons of
crustaceans are produced by fishery or farming for
human consumption, the majority of it being shrimps
and prawns. Krill and copepods are not as widely
fished, but are the animals with the greatest biomass on
the planet and form a vital part of the food chain. The
scientific study of crustaceans is known as carcinology
(alternatively, malacostracology, crustaceology or
crustalogy) and a scientist who works in carcinology is
a carcinologist (Alan and James, 2001).
The body of a crustacean is composed of body
segments, which are grouped into three regions: the
cephalon or head, the thorax and the pleon or abdomen.
23 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
crustaceans (such as the Christmas Island red crab)
mate seasonally and return to the sea to release the
eggs. Others, such as woodlice, lay their eggs on land,
albeit in damp conditions. In most decapods, the
females retain the eggs until they hatch into freeswimming larvae (Elizabeth, 1997).
The majority of crustaceans are aquatic, living in
either marine or fresh water environments, but a few
groups have adapted to life on land, such as terrestrial
crabs, terrestrial hermit crabs and woodlice. Marine
crustaceans are as ubiquitous in the oceans as insects
are on land. The majority of crustaceans are also motile,
moving about independently, although a few taxonomic
units are parasitic and live attached to their hosts
(including sea lice, fish lice, whale lice, tongue worms
and Cymothoa exigua, all of which may be referred to
as "crustacean lice") and adult barnacles live a sessile
life-they are attached headfirst to the substrate and
cannot move independently. Some branchiurans are
able to withstand rapid changes of salinity and will also
switch hosts from marine to non-marine species. Krill
are the bottom layer and the most important part of the
food chain in Antarctic animal communities. Some
crustaceans are significant invasive species, such as the
Chinese mitten crab and the Asian shore crab (Jell,
1980).
These are aquatic free-living animals; they include
the familiar crabs, prawn, lobsters, barnacles and water
fleas. A crustacean has a chitinous exoskeleton that
may be impregnated with hard calcareous material. Its
body has a head and a thorax, which are often fused to
form cephalothorax. The abdomen has eleven segments.
The head bears jointed fellers of antennae, stalked
compound eyes and jointed mouths parts (mandibles
and maxillae). The thorax and abdomen bear jointed
appendages for walking, swimming or reproduction. A
crustacean carries out gaseous exchange through gills.
The name "crustacean" dates from the earliest works to
describe the animals, including those of Pierre Belon
and Guillaume Rondelet, but the name was not used by
some later authors, including Carl Linnaeus, who
included crustaceans among the "Aptera" in his
Systema Naturae. The earliest nomenclaturally valid
work to use the name "Crustacea" was Morten Thrane
Brünnich's Zoologiæ Fundamenta in 1772, although he
also included chelicerates in the group.
The subphylum Crustacea (Plate 18) comprises
almost 67,000 described species, although the number
of undescribed species may be 10-100 times higher.
Although most crustaceans are small, their morphology
varies greatly and they include both the largest
arthropod in the world, the Japanese spider crab with a
leg span of 14 ft (4.3 m) and the smallest-the 0.1 mm
Plate 17: A shed carapace of a lady crab, part of the hard
exoskeleton
The head and thorax may be fused together to form a
cephalothorax, which may be covered by a single large
carapace (Plate 17). The crustacean body is protected
by the hard exoskeleton, which must be moulted for the
animal to grow. The shell around each somite can be
divided into a dorsal tergum, ventral sternum and a
lateral pleuron. Various parts of the exoskeleton may be
fused together. Each somite, or body segment can bear
a pair of appendages: on the segments of the head, these
include two pairs of antennae, the mandibles and
maxillae; the thoracic segments bear legs, which may
be specialized as pereiopods (walking legs) and
maxillipeds (feeding legs). The abdomen bears
pleopods and ends in a telson, which bears the anus and
is often flanked by uropods to form a tail fan. The
number and variety of appendages in different
crustaceans may be partly responsible for the group's
success. Crustacean appendages are typically biramous,
meaning they are divided into two parts; this includes
the second pair of antennae, but not the first, which is
uniramous. It is unclear whether the biramous condition
is a derived state which evolved in crustaceans, or
whether the second branch of the limb has been lost in
all other groups. Trilobites, for instance, also possessed
biramous appendages.
The main body cavity is an open circulatory
system, where blood is pumped into the haemocoel by a
heart located near the dorsum. Malacostraca have
haemocyanin as the oxygen-carrying pigment, while
copepods, ostracods, barnacles and branchiopods have
haemoglobins. The alimentary canal consists of a
straight tube that often has a gizzard-like "gastric mill"
for grinding food and a pair of digestive glands that
absorb food; this structure goes in a spiral format.
Structures that function as kidneys are located near the
antennae. A brain exists in the form of ganglia close to
the antennae and a collection of major ganglia is found
below the gut. In many decapods, the first (and
sometimes the second) pair of pleopods are specialised
in the male for sperm transfer. Many terrestrial
24 Innt. J. Fish. Aquuat. Sci., 1(1): 16-34,
1
2012
Copepods
(
(Cladocera)
Decapods
Amphipod
(Sessiliaa)
C
Cylindroleberidid
dae
Krill
Plate 18: Soome examples off crustaceans
Eggs of
o potamon fluviaatile, a freshwateer crab
Zoea larvaa of the Europeann lobster Homarrus gammarus
ustaceans
Plate 19 Larrval forms of cru
(0.004 in) long Stygotaantulus stockii. Despite thheir
diversity of
o form, crustacceans are uniteed by the speccial
larval form
m known as th
he nauplius (A
Alan and Jam
mes,
1991).
The exact relationsh
hips of the Crrustacea to othher
taxa are noot yet entirely clear. Under the Pancrustaccea
hypothesiss, Crustacea and Hexapoda (innsects and alliees)
are sister groups.
g
Studiess using DNA sequences
s
tendd to
show a parraphyletic Crusstacea, with thee insects (but not
n
necessarilyy other hexapo
ods) nested within
w
that cladde.
Although the classificattion of crustaaceans has beeen
ocarida and Branchiura,
B
heere
quite variable. Mystaco
s
treaated as
treated as part of Maxxillopoda, are sometimes
wn classes. Siix classes are usually recoggnised:
their ow
The lesss familiar miccroscopic crusttaceans such as
a krill
serve a vital link in the
t aquatic foood chain. Billioons of
these microscopic
m
orgganisms swarm
m the lakes, seaas and
ocean and form the main food foor fish. Howevver, in
brackissh water crabbs of the geenus seasarmaa and
cardisooma are know
wn to dig holles on pond dykes
causingg leakages and seepagees. The leaakages
sometim
mes result in loss of fish and
a water froom the
pond. Cirripedia
C
(barnnacles) grow on
o any hard subbstrate
like booards, sluice gate
g
wall, monnks’ wall and sluice
25 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
grooves. When noticed should be removed manually.
Planktonic crustacean such as copepods, cladocerans
and heparticoids are also dangerous pests. If allowed to
enter the water supply to the incubating tanks, they can
destroy fish eggs. They also compete for oxygen in the
incubator or hatching tanks. Proper screening of water
supply pump can prevent planktonic crustaceans
(Burkenroad,1963).
Eryma mandelslohi, a fossil decapod from the Jurassic
of Bissingen an der Teck, Germany
Crustaceans have a rich and extensive fossil record,
which begins with animals such as Canadaspis and
Perspicaris from the Middle Cambrian age Burgess
Shale. Most of the major groups of crustaceans appear
in the fossil record before the end of the Cambrian,
namely the Branchiopoda, Maxillopoda (including
barnacles and tongue worms) and Malacostraca; there is
some debate as to whether or not Cambrian animals
assigned to Ostracoda are truly ostracods, which would
otherwise start in the Ordovician. The only classes to
appear later are the Cephalocarida, which have no fossil
record and the Remipedia, which were first described
from the fossil Tesnusocaris goldichi, but do not appear
until the Carboniferous. Most of the early crustaceans
are rare, but fossil crustaceans become abundant from
the Carboniferous onwards.
Within the Malacostraca, no fossils are known for
krill, while both Hoplocarida and Phyllopoda contain
important groups that are now extinct as well as extant
members (Hoplocarida: mantis shrimp are extant, while
Aeschronectida are extinct; Phyllopoda: Canadaspidida
are extinct, while Leptostraca are extant. Cumacea and
Isopoda are both known from the Carboniferous, as are
the first true mantis shrimp. In the Decapoda, prawns
and polychelids appear in the Triassic and shrimp and
crabs appear in the Jurassic; however, the great
radiation of crustaceans occurred in the Cretaceous,
particularly in crabs and may have been driven by the
adaptive radiation of their main predators, bony fish.
The first true lobsters also appear in the Cretaceous.
The majority of crustaceans have separate sexes
and reproduce sexually. A small number are
hermaphrodites, including barnacles, remipedes and
Cephalocarida. Some may even change sex during the
course of their life. Parthenogenesis is also widespread
among crustaceans, where viable eggs are produced by
a female without needing fertilisation by a male. This
occurs in many branchiopods, some ostracods, some
isopods and certain "higher" crustaceans, such as the
Marmorkrebs crayfish. In many groups of crustaceans,
the fertilised eggs are simply released into the water
column, while others have developed a number of
mechanisms for holding on to the eggs until they are
ready to hatch. Most decapods carry the eggs attached
to the pleopods, while peracarids, notostracans,
anostracans and many isopods form a brood pouch from
the carapace and thoracic limbs. Female Branchiura do
not carry eggs in external ovisacs but attach them in
rows to rocks and other objects. Most leptostracans and
krill carry the eggs between their thoracic limbs; some
copepods carry their eggs in special thin-walled sacs,
while others have them attached together in long,
tangled strings.
Crustaceans exhibit a number of larval forms (Plate
19), of which the earliest and most characteristic is the
nauplius. This has three pairs of appendages, all
emerging from the young animal's head and a single
naupliar eye. In most groups, there are further larval
stages, including the zoea. This name was given to it
when naturalists believed it to be a separate species. It
follows the nauplius stage and precedes the post-larva.
Zoea larvae swim with their thoracic appendages, as
opposed to nauplii, which use cephalic appendages and
megalopa, which use abdominal appendages for
swimming. It often has spikes on its carapace, which
may assist these small organisms in maintaining
directional swimming. In many decapods, due to their
accelerated development, the zoea is the first larval
stage. In some cases, the zoea stage is followed by the
mysis stage and in others, by the megalopa stage,
depending on the crustacean group involved.
Many crustaceans are consumed by humans and
nearly 10,700,000 tons were produced in 2007; the vast
majority of this output is of decapod crustaceans: crabs,
lobsters, shrimp and prawns. Over 60% by weight of all
crustaceans caught for consumption are shrimp and
prawns and nearly 80% is produced in Asia, with China
alone producing nearly half the world's total. Nondecapod crustaceans are not widely consumed, with
only 118,000 tons of krill being caught, despite krill
having one of the greatest biomasses on the planet.
Molluscs: About half the molluscs are marine animals,
the rest live in fresh water or on land (Harper et al.,
2006). They include the snails, (bivalves, mussels,
calms scallops and oysters), octopuses and squids. Man
eats most molluscs as food. A mollucs has a soft
unsegemented body with a muscular food, which may
be adapted for crawling, burrowing or swimming. A
soft tissue called the mantle covers the body. The
mantle cavity is found between the mantle and the body
mass containing the internal organs. The anus opens
into the mantle cavity. A mollucs carries out gaseous
exchange through gills or a ‘lung’ in the mantle cavity.
26 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
brackish water and estuarine species) represent about
8,000 species, combined in 4 subclasses and 99 families
with 1,100 genera. The largest recent marine families
are Veneridae with more than 680 species, the
Tellinidae and Lucinidae each with over 500 species.
The freshwater bivalves include 7 families, of which
the Unionidae contain about 700 species. Bivalves have
a shell consisting of two asymmetrically rounded halves
called valves that are mirror images of each other,
joined at one edge by a flexible ligament called the
hinge. The shell is typically bilaterally symmetrical,
with the hinge lying in the sagittal plane. The adult
maximum shell size of recent species of bivalves ranges
from 0.52 mm in Condylonucula maya (a nut clam) to a
length of 1,532 mm in Kuphus polythalamia, a kind of
shipworm. However, the species generally regarded as
the largest living bivalve is the giant clam Tridacna
gigas which can weigh more than 200 kg (441 lbs).
Bivalves are unique among the Mollusca in that
they have lost their odontophore and radula in their
transition to filter feeding. Some bivalves are epifaunal;
they attach to surfaces. Others are infaunal; they bury
themselves in sediment. These forms typically have a
strong digging foot. Some bivalves such as scallops can
swim (Huber, 2010).
Many systems have been developed for the
classification of bivalves, but for the past two centuries
no professional consensus has existed on bivalve
phylogeny (Vaught, 1989). In the earlier taxonomic
systems experts used only one characteristic feature for
their taxonomic system, either shell morphology, hinge
type, or the type of gills. Many conflicts existed due to
taxonomies based on single organ systems and
conflicting naming schemes proliferated. One of the
most widely accepted systems was that of Newell in the
Treatise on Invertebrate paleontology, which employed
a classification system based on general shell shape,
microstructures and hinge configuration. Since features
such as hinge morphology, dentition, mineralogy and
shell morphology and composition change slowly these
characteristics can be used for defining major
taxonomic groups. Due to the numerous fossil lineages,
DNA sequence data is of limited use in classifying
extinct species (Bouchet et al., 2010).
In the last decade, taxonomic studies using
cladistical analyses of multiple organ systems, shell
morphology (including species in the fossil record) and
modern molecular phylogenetics have drawn what
experts believe to be a more accurate phylogeny of the
Bivalvia. Based upon these studies a new proposed
classification system for the Bivalvia (Taylor et al.,
2011). Currently, in 2012, this new taxonomic
Plate 20: Some bivalve: (htt://en.wikipedia.org/wiki/file:
Haeckel_Acepala.jpg)
Many molluscs such as the snails and the bivalves have
outer calcareous shells secreted by the mantle. These
shells protect them from physical damages, predators
and dying out. Mollucs reproduces sexually. The sexes
are usually separate. Bivalves (Plate 20) grow on hard
substrates and snails on the pond bottom. In brackish
waters, Crassostea gasar (oysters) grow on pond
grooves and can close the pond screens. In fresh water,
the bivalve, Etheria, can cause pond screen closure.
Neritina, Thias callifera and Tympanotumus fuscatus
occur in brackish water pond bottom, competing for
food and space with fish. Excess of these molluscs
disturb the pond ecological system because they can
cover the pond bottom and prevent the pond mud from
releasing nutrient. Mullusc can be handpicked from the
pond. Chemicals can also be applied to kill them
(Mikkelsen et al., 2006). The term bivalve is derived
from the Latin bis, meaning 'two' and valvae, meaning
leaves of a door. Not all animals that have two hinged
shells are Bivalvia; other kinds include the bivalved
gastropods (small sea snails in the family Juliidae), the
phylum Brachiopoda and the minute crustaceans known
as ostracodes and conchostrachans. Bivalvia (common
name bivalves) is a taxonomic class of marine and
freshwater molluscs that have a shell in two hinged
parts. This class includes clams, oysters, mussels,
scallops and many other families. The name Bivalvia
was first used by Linnaeus in 1758, describing the shell,
which is composed of two valves. More recently the
class was known for a time as Pelecypoda, meaning
"axe-foot" based on the soft parts of the animal. Other
names which have been used for this class include
Lamellibranchia (based on the plate-like gill elements,
see ctenidium), Acephala (these animals have no head)
and Bivalva (two valves).
The total number of bivalve species is currently
approximately 9,200. These are placed within 1,260
genera and 106 families. Marine bivalves (including
27 Innt. J. Fish. Aquuat. Sci., 1(1): 16-34,
1
2012
Fig. 1: A diaagram of the inteernal shell anatoomy of the left haand valve of a biivalve
cerebroopleural gangliia on either sidde of the oesophhagus.
The peedal ganglia, controlling the foot, are at its base
and thee visceral ganglia (which caan be quite laarge in
swimm
ming bivalves)) under the posterior adductor
muscle (Jay, 2001). These
T
ganglia are
a both conneccted to
the cerrebropleural gaanglia by nervve fibres. There may
also bee siphonal gangglia in bivalvess with a long siphon.
The sennsory organs of
o bivalves aree not well deveeloped
and arre largely a function
f
of thhe posterior mantle
m
marginns (Bieler and Mikkelsen,
M
20006).
Thhe organs are usually
u
tentaclle mechanorecceptors
or chem
moreceptors. Scallops
S
have complex
c
eyes with
w a
lens annd retina, but most other bivalves
b
have much
simplerr eyes, if any. There are alsoo light-sensitivee cells
in all bivalves
b
that caan detect a shaadow falling ovver the
animal.. Many bivalvves possess a number
n
of tenntacles,
which have chemoreeceptor cells too taste the water, as
well ass being sensitive to touch. These are typpically
found near
n
the siphonns, but in somee species may fringe
the entiire mantle caviity. Another nootable sensory organ
found in
i bivalves is the
t osphradium
m, a patch of seensory
cells loocated below the posterior adductor muscle. It
may seerve to taste thhe water, or measure
m
its turbbidity,
but it is probably nott homologous with
w the structture of
the sam
me name fouund in snails and slugs. In
I the
septibraanchs the inhhalant siphon is surroundeed by
vibratioon-sensitive tentacles forr detecting prey.
Statocyysts within the organism helpp the bivalve too sense
and coorrect its orienntation. The muscular
m
systtem is
compossed of the posterior
p
andd anterior adductor
muscles, although thee anterior musccles may be reeduced
or evenn lost in some species.
s
The paaired anterior and
a
Fig. 2: Mainn parts in the sheell of a bivalve; 1: sagittal plane,, 2:
grow
wth lines, 3: ligam
ment, 4: umbo
classificatiion system has been recognizzed by the World
Register of
o Marine Species (WooRMS) as the
t
classificatiion system for the Bivalvia (S
Schneider, 2001).
Some expeerts still maintain that the Annomalodesmaccea
is a separrate Subclass. Others place it as the Ordder
Anomalodesmata within
n the Heteroddonta. Molecuular
phylogeny work conttinues, furtheer refining the
t
taxonomy of the Bivalviaa (Bieler et al., 2010).
Bivalvve shells (Fig. 1 and 2) vary greatly in shappe;
some are globular, otheers flattened, while
w
others are
a
wing. The shhipworms of the
t
elongated to aid burrow
family Terredinidae havee greatly elonggated bodies, but
b
the shell valves
v
are much reduced andd restricted to the
t
anterior ennd of the bo
ody, where thhey function as
burrowing organs that peermit the anim
mal to dig tunnels
through woood. The sedentary habit of the bivalves has
h
led to the development of a simpler nervous systeem
than in othher molluscs; th
hey have no brain. In all but the
t
simplest foorms the neural ganglia are united into tw
wo
28 Innt. J. Fish. Aquuat. Sci., 1(1): 16-34,
1
2012
usuallyy lacks any respiratory pigm
ment, although some
speciess are known to
t possess haeemoglobin disssolved
directlyy into the serum
m (Akira, 20100).
Thhe world's largest clam
m (187 cmss), a
Sphenooceramus steennstrupi fossil frrom Greenlandd in the
Geologgical Museum in Copenhaggen. In bivalvees the
mantle forms a thin membrane suurrounding thee body
v
ligameent and hinge teeth.
which secretes the valves,
The maantle lobes secrrete the valves and the mantlee crest
secretes the ligamennt and hinge teeth. The manntle is
attached to the shell by the mantle retractor musccles at
me bivalves thhe mantle edgees fuse
the palllial line. In som
to form
m siphons, whhich take in and
a
expel watter for
suspenssion feeding. The shell is composed of
o two
calcareous valves, whhich are made of either calcite (as
with oyysters) or both calcite and araagonite, usuallyy with
the araagonite forminng an inner layer (as witth the
Pterioidda). The outeermost layer is
i the periostrracum,
compossed of a hornyy organic substaance. This form
ms the
familiaar coloured layyer on the shelll. The shell is added
to in two
t
ways; at the open edgee and by a gradual
g
thickenning throughouut the animal's life.
l
The shell halves
h
are heeld together at
a the animal's dorsum by
b the
ligamennt, which is composed off the tensilium
m and
resilium
m. The ligameent passively opens
o
the shelll. The
shell is closed activelly by using addductor muscless (or in
c
one muscle) that are attached
a
to thee inner
some cases
surfacee of both valvves. The position of the adductor
muscle or muscles iss often quite clearly visible on
o the
o an empty valve,
v
as a circcular or oval muscle
m
inside of
scar or scars.
Thhe majority off bivalves are filter feeders, using
their giills to capture particulate
p
foood from the waater. In
almost all species, the
t water currrent enters thee shell
from thhe posterior ventral
v
surfacee of the animaal and
then paasses upwards through the gills in a U-shaape, so
that it exits
e
just above the intake. Inn burrowing sppecies,
there may
m be elongated siphons stretching from the
body to
t the surfacee, one each foor the inhalannt and
exhalannt streams of water. The giills of filter-feeeding
bivalvees have become highly modiffied to increase their
ability to capture foood. For exampple, the cilia on
o the
gills, which
w
originaally served too remove unw
wanted
sediment, are adapteed to capture food particlees and
transpoort them in a steady stream
m of mucus to
t the
mouth. The filamentss of the gills are
a also much longer
than thhose in more primitive
p
bivaalves and are folded
over too create a grooove through which food can
c be
transpoorted. The structure of the gills varies
consideerably and caan serve as a useful meanns for
classifyying bivalves into
i
groups (T
Taylor and Suzzanne,
2007).
Fig. 3: Fourr filaments of thee gills of the bluee mussel (Mytiluus
edullis)
posterior pedal
p
retractorr muscles operrate the animaal's
foot. In soome bivalves, such as oysteers and scallopps,
these retraactors are abssent. Bivalvess have an oppen
circulatoryy system th
hat bathes the
t
organs in
hemolympph. The heart haas three chambbers: two auricles
receiving blood
b
from th
he gills and a single ventriccle.
The ventriicle is musculaar and pumps hemolymph innto
the aorta and
a through thiis to the rest off the body. Maany
bivalves haave only a sing
gle aorta, but most
m also havee a
second, usually smaller, aorta serving the hind parts of
the animal (Giribet and Wheeler,
W
2002)).
t
blue mussel
Four filaments of the gills of the
(Mytilus eddulis):



Part of four filaments
f
shhowing ciliatted
interfilamentar juncttions (cj)
gle filament shhowing the tw
wo
Diagraam of a sing
lamelllae connected at intervals by interlamelllar
junctioons (ilj)
The position of the interfilaamentar ciliatted
junctioons (cp) (Fig. 3).
3
d into the hem
molymph in the
t
Oxygeen is absorbed
gills, which hang down into
i
the mantlee cavity and allso
assist in filtering
f
food particles from
m the water. The
T
wall of thhe mantle cavity is a seconndary respiratoory
surface annd is well sup
pplied with capillaries.
c
Som
me
species, hoowever, have no
n gills, with the
t mantle cavvity
being the only location
n of gas excchange. Bivalvves
adapted too tidal environ
nments can surrvive for seveeral
hours out of water by cllosing their shhells and keepiing
the mantlee cavity filled
d with water. The hemolym
mph
29 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
bivalves start life as a trochophore, later becoming a
veliger. Freshwater bivalves of the Unionoida have a
different life cycle: they become a glochidium, which
attaches to any firm surface to avoid the danger of
being swept downsteam. Glochidia can be serious pests
of fish if they lodge in the fish gills. Some of the
species in the freshwater mussel family, Unionidae,
commonly known as pocketbook mussels have evolved
a remarkable reproductive strategy. The edge of the
female's body that protrudes from the valves of the shell
develops into an imitation of a small fish complete with
markings and false eyes. This decoy moves in the
current and attracts the attention of real fish. Some fish
see the decoy as prey, while others see a conspecific.
Whatever they see, they approach for a closer look and
the mussel releases huge numbers of larvae from her
gills, dousing the inquisitive fish with her tiny, parasitic
young. These glochidia larvae are drawn into the fish's
gills where they attach and trigger a tissue response that
forms a small cyst in which the young mussel resides. It
feeds by breaking down and digesting the tissue of the
fish within the cyst (Taylor et al., 2007).
The radical structure of the bivalves reflects their
behaviour in several ways. The most significant is the
use of the closely fitting valves as a defence against
predation and, in intertidal species, against desiccation.
The entire animal can be contained within the shell,
which is held shut by the powerful adductor muscles.
This defence is difficult to overcome except by
specialist predators such as sea stars and oystercatchers.
Most bivalves are filter feeders although some have
taken up scavenging and predation. Nephridia remove
the waste material. Buried bivalves feed by extending a
siphon to the surface (indicated by the presence of a
pallial sinus, the size of which is proportional to the
burrowing depth and represented by their hinge teeth).
There are four feeding types, defined by their gill
structure: Protobranchs use their ctenidia solely for
respiration and the labial palps to feed. Septibranchs
possess a septum across the mantle cavity which pumps
in food. Filibranchs and lamellibranchs trap food with a
mucous coating on the ctenidia; the filibranchs and
lamellibranchs are differentiated by the way the
ctenidia are joined (Klaus, 1994).
Razor shells can dig themselves into the sand with
great speed to escape predation. Scallops and file clams
can swim to escape a predator, clapping their valves
together to create a jet of water. Cockles can use their
foot to leap from danger. However these methods can
quickly exhaust the animal. In the razor shells the
siphons can break off only to grow back later. The file
shells can produce a noxious secretion when threatened
Some bivalves feed by scraping detritus from the
bottom and this may be the primitive mode of feeding
for the group, before the gills became adapted for filter
feeding. These primitive bivalves hold onto the
substratum with a pair of tentacles at the edge of the
mouth, each of which has a single palp, or flap. The
tentacles are covered in mucus, which traps the food
particles and transports them back to the palps using
cilia. The palps then serve to sort the particles, ejecting
those that are too large to be digestible. A few bivalves,
such as Poromya, are carnivorous, eating much larger
prey than the tiny phytoplankton consumed by the filter
feeders. In these animals, the gills are relatively small
and form a perforated barrier separating the main
mantle cavity from a smaller chamber through which
the water is exhaled. Muscles pump water through the
cavity, sucking in small crustaceans and worms. The
prey are then seized in the palps and consumed. The
unusual genus Entovalva is parasitic and lives only in
the gut of sea cucumbers.
The digestive tract of typical bivalves consists of
an oesophagus, stomach and intestine. A number of
digestive glands open into the stomach, often via a pair
of diverticula; these secrete enzymes to digest food in
the stomach, but also include cells that phagocytose
food particles and digest them intracellularly. In the
filter feeding bivalves, an elongated rod of solidified
mucus referred to as the crystalline style projects into
the stomach from an associated sac. Cilia in the sac
cause the style to rotate, winding in a stream of foodcontaining mucus from the mouth and churning the
stomach contents. This constant motion propels food
particles into a sorting region at the rear of the stomach,
which distributes smaller particles into the digestive
glands and heavier particles into the intestine.
Carnivorous bivalves have a greatly reduced style and a
chitinous gizzard that helps grind up the food before
digestion (Taylor et al., 2009).
Like most other molluscs, the excretory organs of
bivalves are nephridia. There are two nephridia, each
consisting of a long, glandular tube, which opens into
the body cavity just beneath the heart and a bladder.
Waste is voided from the bladders through a pair of
openings near the front of the upper part mantle cavity,
where it can easily be washed away in the stream of
exhalant water.
The sexes are usually separate, but some
hermaphroditism is known. Bivalves practice external
fertilization. The gonads are located close to the
intestines and either open into the nephridia, or through
a separate pore into the mantle cavity. Typically
30 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
and the fan shells of the same family have a unique,
acid-producing organ.
Bivalves are superficially similar to brachiopods,
which also have a shell consisting of two valves, but the
construction of the shell is completely different in the
two groups. In brachiopods, the two valves are on the
dorsal and ventral surfaces of the body, while in
bivalves, they are on the left and right sides. Bivalves
appeared late in the Cambrian explosion and came to
dominate over brachiopods during the Palaeozoic. By
the Permian-Triassic extinction event bivalves were
undergoing a huge radiation while brachiopods were
devastated, losing 95% of their diversity. It had long
been considered that bivalves are better adapted to
aquatic life than the brachiopods were, causing
brachiopods to be out-competed and relegated to minor
niches in later strata. These taxa appeared in textbooks
as an example of replacement by competition. Evidence
included the use of an energetically efficient ligamentmuscle system for opening valves, requiring less food
to subsist. However the prominence of bivalves over
brachiopods might instead be due to chance disparities
in their response to extinction events.
Plate 21: Frog
Plate 22: Toad
newts differ from frogs and toads in having slender,
elongated bodies with necks and long tail. Some frogs
live on fish fry and are therefore harmful. They lay eggs
on the surface of ponds. Large masses of eggs consume
much pond oxygen. This can retard fish growth if not
checked. Many cannot differentiate frogs from toads.
They are quite different animals, although they belong
to the same animal group (Table 1). Neither frogs nor
toads will give you warts! That is just a myth.
Generally speaking, though, when we think of frogs, we
generally picture what are called "True Frogs"members
of the family Ranidae, containing more than 400
species. These frogs have the characteristics of:
AMPHIBIANS:
These are believed to have evolved from an ancient
group of lobe-finned fishes. They were the first
vertebrates to venture out of the water and live on land.
Present day amphibians include the frogs, toads, newts
and salamanders. Most of them live in moist
environments and return to water to breed. An
amphibian has these features: It is cold blooded; it has
paired fore and hind limbs in the adult stage. It has a
naked, most skin. It has a sticky tongue, which can be
protruded and retracted quickly. It has inner and middle
ears. It carries out gaseous exchange by gills, lungs,
skin or mouth lining, separately or in combination. Gills
are present at some stage in its life cycle. It has a-three
chambered heart. An aquatic lava stage is usually
present.
Frogs (Bufalo bufalo) (Plate 21) and toads
(Xenopus) (Plate 22) are the largest group of
amphibians. They have stout bodies with powerful hind
legs for leaping and webbed feet for swimming. They
mate in water. During mating, the male climbs on the
female’s back. The male releases sperm cells to fertilize
eggs as soon as laid. The embryos of the fertilized eggs
develop into fish like larvae called tadpoles, which
undergo metamorphoses to become adult amphibians.
Tadpoles feed on aquatic plants and animals while frogs
and toads feed on insects and worms. Salamander and




Frogs from this family can be found on every
continent except Antarctica. They are referred to as the
"true frogs" because of their generalized body form and
life history: the so-called generic frog. Members of this
family include the bullfrog, common frog, green frog,
leopard frog, marsh frog, pickerel frog and wood frog.
The term toads tend to refer to "True Toads"
members of the family Bufonidae, containing more than
300 species. These types of frogs have are characterized
by:
31 Two bulging eyes
Strong, long, webbed hind feet that are adapted for
leaping and swimming
Smooth or slimy skin (generally, frogs tend to like
moister environments)
Frogs tend to lay eggs in clusters
Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
Table 1: Difference between frogs and toads Frog
Need to live near water
Have smooth, moist skin that makes them look “slimy”
Have a narrow body
Have higher, rounder, bulgier eyes
Have longer hind legs
Take long high jumps
Have many predators





Toad
Do not need to live near water to survive
Have rough, dry, bumpy skin
Have a wider body
Have lower, football shaped eyes
Have shorter, less powerful hind legs
Will run or take small hops rather than jump
Do not have many predators. Toad’s skin lets out a bitter taste and
smell that burns the eyes and nostrils of its predators, much like a
skunk does

Stubby bodies with short hind legs (for walking
instead of hopping)
Warty and dry skin (usually preferring dryer
climates)
Paratoid (or poison) glands behind the eyes
The chest cartilage of toads is different also
Toads tend to lay eggs in long chains. (There are
some toads (genera Nectophrynoides), however,
that are the only types of anurans to bear live
young!)




True Toads can be found worldwide except in
Australasia, polar regions, Madagascar and Polynesia,
though Bufo marinus has been artificially introduced
into Australia and some South Pacific islands. Besides
Bufo, the family includes 25 genera, all of which, like
the frogs, are anura! The physical distinctions, however,
can easily get blurred because sometimes the features
appear mixed or less obvious and certain species even
legitimately fall into both categories. It is not
uncommon, for example, to find a warty skinned frog
that isn't a toad, or even a slimy toad! Even the more
invisible stuff like cartilage structure has been found to
sometimes fit both categories!


CONCLUSION
Predatory fish, aquatic birds, aquatic mammals and
some other animals (toads, coelenterates and
crustaceans) are some challenges to culture fisheries in
Nigeria. These pests of fish destroy fish or hinder the
production of target fish species. Man also pouches on
fishponds. However some pests to culture fisheries are
also useful in culture fisheries management and
practices. The management of the pest is essential for
the sustenance of culture fisheries in Nigeria.
Control of Crustaceans, Predatory Fishes, Aquatic
Birds and Mammals: Fish predators can be controlled
by the following methods.






REFERENCES
Traps can be set for crabs, fishes, birds and
mammals that prey on fish in the pond.
Birds and mammals can be shot with gun. Aerial
traps are efficient for birds.
Birds and mammals can be chased away manually
Proper screening is necessary to stop predatory fish
from entering the pond. The pond can be netted to
catch and remove predatory fish.
Predatory reptiles can be trapped with basket traps
and killed
Fence the pond area
Akira, S., 2010. Closed and Open Circulatory System.
Georgia State University, Retrieved from:
http://www2.gsu.edu/~bioasx/closeopen.html,
(Accessed on: November 26, 2010).
Alan, P.C. and H.T. James, 1991. Crustacea:
Introduction and Peracarida. In: James, H.T. and
P.C. Alan., (Eds.), Ecology and Classification of
North American Freshwater Invertebrates. 1st
Edn., Academic Press, San Diego, pp: 665-722,
ISBN: 978-0-12-690645-5.
32 Trusted security can be employed to check
pouching by man
Animal pest in the fishpond can be controlled
physically, manually or chemically. These can be
done in the following ways:
Do not place nursery ponds under water for more
than 2 days before stocking. This can hinder the
development of harmful larva.
Allow pond to dry for a long period before
stocking. This can destroy insect pests.
Manual removal of mollucs from the pond bottom
reduces the pest.
Suitable insecticides such as DDT can be used to
eliminate insect pests.
Pond clearing agents such as quick lime, bleaching
powder and rotenone can also eradicate some
animal pests.
Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
Alan, P.C. and H.T. James, 2001. Introduction to the
Subphylum Crustacea. In: H.T. James and P.C.
Alan, (Eds.), Ecology and Classification of North
American Freshwater Invertebrates. 2nd Edn.,
Academic Press, San Diego, pp: 777-798,
ISBN: 978-0-12-690647-9.
Barnes, R.D., 1982. Invertebrate Zoology. HoltSaunders
International,
Philadelphia,
PA,
pp: 389-430, ISBN: 0-03-056747-5.
Bieler, R. and P.M. Mikkelsen, 2006. Bivalvia-a look at
the branches. Zool. J. Linn. Soc., 148: 223-235.
Bieler, R., J.G. Carter and E.V. Coan, 2010.
Classification of bivalve families. pp: 113-133.
Cited in: Bouchet, et al., 2010.
Bouchet, P., J.P. Rocroi, R. Bieler, J.G. Carter and E.V.
Coan, 2010. Nomenclator of bivalve families: With
a classification of bivalve families, Malacologia,
52(2): 1-184.
Burkenroad, M.D., 1963. The evolution of the Eucarida
(Crustacea, Eumalacostraca), in relation to the
fossil record. Tulane Stud. Geol., 2(1): 1-17.
Elizabeth, P., 1997. Crab legs and lobster claws. Sci.,
277(5322): 36.
Giribet, G. and W. Wheeler, 2002. On bivalve
phylogeny: A high-level analysis of the Bivalvia
(Mollusca) based on combined morphology and
DNA sequence data. Invertebr. Biol., 121(4):
271-324.
Global Environmental Monitoring System (GEMS),
1992. An Operational Guide, 3rd Edn.
Happold, D.C.D, 1987. Mammals of Nigeria.
Clerendon Press Oxford, UK.
Harper, E., D. Hermann and S. Gerhard., 2006.
Reconstructing the anomalodesmata (Mollusca:
Bivalvia): Morphology and molecules. Zool. J.
Linn. Soc., 148(3): 395-420.
Hayward, P.J. and J.S. Ryland, 1995. Handbook of the
Marine Fauna of North-West Europe. Oxford
University
Press, Oxford, ISBN: 978-0-19854055-7.
Huber, M., 2010. Compendium of Bivalves. A FullColor Guide to 3'300 of the World's Marine
Bivalves. A Status on Bivalvia after 250 Years of
Research. Conch Books, Hackenheim, pp: 901 +
CD, ISBN: 978-3-939767-28-2.
Hughes, N.C., 2003. Trilobite tagmosis and body
patterning from morphological and developmental
perspectives. Integr. Comp. Biol., 43(1): 185-206.
International Union for the Conservation of Nature and
Natural Resources (IUCN), 1992. Coastal and
Marine
Biodiversity
Report
for
UNEP:
Identification, Establishment and Management of
Specially Protected Areas in the WACAF Region.
Gland, Switzerland.
Jay, A.S., 2001. Bivalve systematics during the 20th
century. J. Paleontol., 75(6): 1119-1127.
Jell, P., 1980. Earliest known pelecypod on Earth-a new
Early Cambrian genus from South Australia
Alcheringa an Australasian. J. Palaeontol., 4(3):
233-226.
Klaus, U., 1994. Respiratory Pigments. Comparative
Animal Biochemistry. Springer, pp: 249-287,
ISBN: 978-3-540-57420-0.
Limkpe, B.H., 1991. Introduction. Marine Lobsters of
the World, FAO Species Catalogue.
Margulis, L. and V.S. Karlene, 1997. Five Kingdoms:
An Illustrated Guide to the Phyla of Life on Earth,
W.H. Freeman and Co., New York, ISBN: 0-61392338-3.
Mikkelsen, P.M., R. Bieler, I. Kappner and T.A.
Rawlings, 2006. Phylogeny of Veneroidea
(Mollusca: Bivalvia) based on morphology and
molecules. Zool. J. Linn. Soc., 148(3): 439-521.
Niger Delta Environmental Survey (NDES), 1997.
Final Report of Phase 1. Vol. 1.
Niger Delta Environmental Survey (NDES), 2003.
Phase 1 Report on the Niger Delta Environment.
Oates, J.F., R.A. Bergl and J.M. Linder, 2004. Africa’s
Gulf of Guinea Forests: Biodiversity Patterns and
Conservation Priorities. Advances in Applied
Biodiversity Science No. 6, Center for Applied
Biodiversity, Washington, pp: 90.
Ponder, W.F. and D.R. Lindberg, 2008. Phylogeny and
Evolution of the Mollusca. University of California
Press, Berkeley, pp: 117, ISBN: 0520250923.
Runnegar, B., 1983. Anatomy, ecology and affinities of
the australian early cambrian bivalve pojetaia
runnegari jell. J. Paleontol. Paleontol. Soc., 57(1):
73-92.
Schneider, J.A., 2001. Bivalve systematics during the
20th century. J. Paleontol., 75(6): 1119-1127.
Taylor, J.D., S.T. Williams, E.A. Glover and P. Dyal.,
2007. A molecular phylogeny of heterodont
bivalves (Mollusca: Bivalvia: Heterodonta): New
analyses of 18S and 28S rRNA genes, Zool. Scr.,
36(6): 587-606.
Taylor, J.D., E.A. Glover and S.T. Williams., 2009.
Phylogenetic position of the bivalve family
Cyrenoididae-removal
from
(and
further
dismantling of) the superfamily Lucinoidea.
Nautilus, 123(1): 9-13.
33 Int. J. Fish. Aquat. Sci., 1(1): 16-34, 2012
Taylor, J.D., E.A. Glover, P. Dyal and S.T. Williams,
2011. Molecular phylogeny and classification of
the chemosymbiotic bivalve family Lucinidae
(Mollusca: Bivalvia). Zool. J. Linn. Soc., 163:
15-49.
Vaught, K.C., 1989. A Classification of the Living
Mollusca. American Malacologists, Melbourne,
FL, USA, ISBN: 0-915826-22-4. 12, pp: 195.
34