Prawn Honours projects for 2014
Western School Prawns (Metapenaeus dalli) were once the focus of an iconic recreational
and commercial fishery in the Swan-Canning Estuary. However, their numbers have declined
since the 1960s. As a result, Murdoch University together with the Swan River Trust and the
Challenger Institute of Technology has just received funding to restock the Western School
Prawn in the estuary and investigate the biology and ecology of this species. We have several
exciting Honours projects available, which focus on different aspect of the prawns.
Determination of the age and growth of prawns using eyestalks
The counting of annual growth bands deposited in
hard structures, such as the otoliths (ear bones) of
fishes and shells of bivalves underlies the assessment
and management of fisheries across the world. Such
measurements have not yet been applied to
crustaceans, as they were thought to lack permanent
hard growth structures due to the moulting of their
exoskeleton which occurs regularly. However, a recent
study of two prawns, a crab and a lobster from North America have revealed that growth
bands similar to those in fish otoliths are found in calcified regions of the eyestalk and/or
gizzard (Kilada et al., 2012). This project, which would be an Australian first, would allow
the assessment of the current stock structure of Western School Prawns (Metapenaeus dalli)
and Western King Prawns (Melicertus latisulcatus), something, which despite the decline in
abundance of this species, has never been able to be undertaken before now. The aims of this
Honours project are to investigate the stock structure of prawns in the Swan-Canning Estuary
and determine whether it’s possible to age prawns using calcified regions of their eye stalks.
Snow Crab
(Chionoecetes opilio),
Northern Shrimp
(Pandalus borealis)
American Lobster
(Homarus Americanus)
Examples of the growth bands found crustacean species. Taken from Kilada et al. (2012).
This project would involve both laboratory and fieldwork and all costs would be covered by a
grant from the Fisheries Research and Development Corporation and Swan River Trust.
Investigating the burrowing habitats and daily routine of the Western School Prawn
Prawns spend a large part of their life in contact with the seabed and, as such, the abundance
of many prawn species has been linked to characteristics of the sediment. Many prawn
species also undergo pronounced diel (day/night) changes in their behaviour; burying
themselves during the day and emerging at night to feed. This burying reduces their energy
expenditure and makes them less susceptible to predation. A multitude of studies conducted
around the world have described the method and depth of burying of multiple prawn species
as well as investigating their daily patterns of emergence and activity. However, despite the
importance of the Western School Prawn (Metapenaeus dalli) to both commercial and
recreational fishers in the Swan-Canning and Peel-Harvey estuaries, very little is known
about the way this species interacts with the sediment and its activity patterns. This project
aims to address these knowledge gaps by:
1) Collecting Western School Prawns from the Swan-Canning Estuary and describing
the method of burying from tank experiments conducted in the laboratory.
2) Comparing rates of and depths of burial among various life stages of the Western
School Prawn.
3) Describing the patterns of emergence and activity in the Western School Prawn under
laboratory conditions (see figure below).
4) Comparing these results with data on prawn abundance collected at regular intervals
throughout the day and night in the Swan-Canning Estuary.
Pattern of emergence (a) and activity (b) of Brown Shrimp (Penaeus aztecus) under
laboratory conditions. Taken from Dall et al. (1990).
If the student wished these techniques could also be applied to the Western King Prawn. This
project would involve both laboratory and fieldwork and all costs would be covered by a
grant from the Fisheries Research and Development Corporation and Swan River Trust.
Determining the contribution of prawns to the diets of fishes in the Swan-Canning Estuary
The abundance of the Western School Prawns
(Metapenaeus dalli) has declined since the
Western King Prawns
1960s, however, there is no clear explanation
as to why this has occurred. One of the factors
hypothesised to have played a role is the
increase in predatory fish species, such as the
Black Bream (Acanthopagrus butcheri) and the
Weeping
Toadfish
(Torquigener
pleurogramma). The aim of this Honours
project is to determine the diets of the above two
key fish species and other potential predators e.g. Gobbleguts (Apogon rueppellii), Whiting
and Flathead species and the Yellow-eye Mullet (Aldrichetta forsteri) and assess what
contribution Western School Prawns make to the diets of those species. Although the diets of
most of these species have been investigated previously, those samples were collected several
decades ago and also during the day. Therefore, as prawns spend the day buried and emerge
at night (during which time they are venerable to predation), the proportion of prawns in the
diets of these fish species may have been underestimated previously. Laboratory feeding
trials will also be conducted using juvenile and adult prawns together with Black Bream,
Weeping Toad fish and the Brown Jellyfish (Phyllorhiza punctata) by a PhD student and the
Honours student would be welcome to use this set up to conduct additional experiments of
their choosing.
This project would involve both laboratory and fieldwork and all costs would be covered by a
grant from the Fisheries Research and Development Corporation and Swan River Trust.
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For more information on any of these projects and to apply please contact Dr James
Tweedley
(j.tweedley@murdoch.edu.au)
and
Professor
Neil
Loneragan
(n.loneragan@murdoch.edu.au).