Are cold water corals an important habitat
for fish? A video analysis of the Irish case
G. Prato, A. Rengstorf, A. Grehan
Earth and Ocean Science, National University of Ireland, Galway
INTRODUCTION
The EU 7th Framework Programme project ‘CoralFISH’ is assessing the interaction between corals, fish and fisheries, in order to develop monitoring and predictive modelling tools for ecosystem based
management in the deep waters of Europe and beyond.
Determining the importance of habitat for fish is not trivial. CoralFISH has adopted a three prong approach: fisheries acoustic surveys, longline experimental fishing and in situ video surveys of coral and
control areas. Here we present the results of CoralFISH video surveys undertaken in Irish waters. The key questions are:
• Is there a significant difference in fish assemblages found in reef areas compared with non-reef areas in terms of species diversity or abundance?
• Is there a significant difference in fish assemblages associated with coral and non-coral three dimensional structures?
VIDEO ANALYSIS
STUDY AREA AND SAMPLING DESIGN
• Video surveys were conducted in three study locations of the west coast of Ireland: Belgica
Mound Province (Porcupine Seabight), Arc M. Province (Southern Porcupine Bank) and
Logachev M. Province (Southern Rockall Bank; Fig.1). Depths ranged from 600 to 1000m.
• Standardised experimental sampling design (CE10014 ROV survey, May 2010):
- 2 km x 2 km experimental boxes in coral and control area,
- random selection of 3 boxes in coral (on mound) and non-coral (off mound) areas
- standardized 2 km ROV-transects within each box
CoralFISH video annotation proprietary software: COVER (Customizable Observation Video imagE Record
Annotations for each segment included:
- Primary (> 50% cover) and secondary (>20 % cover) substrate cover. Substrate categories used: coral
framework, coral rubble, bedrock, boulder, cobble, pebble, gravel and sand (according to a standard
CoralFISH classification system (Kutti et al., 2009). Boulders were always annotated.
- Fish species and abundance
- Fish locomotion activity and position relative to three dimensional objects.
DATA ANALYSIS
Arc
Mounds
a.
• Video segments were grouped into three main habitat types:
- Coral = coral framework, isolated corals and rubble (a)
- 3D geogenic structures = boulders, bedrock and cobbles (b)
- Fine sediment = sand and gravel (c)
• Comparison of % cover of each habitat and species density (fish/m2) per each transect
• Multivariate analysis with PRIMER-6 software were performed to unravel patterns in
fish community structure among habitat types and study sites.
• Relative percentage abundances of each species were plotted to analyse habitat
specificity (n. of individuals per habitat / total n. of individuals from all habitats)
• Locomotion behaviour for the most abundant species among habitat types was
described.
c
Logachev
Fig.1
a. Study area
b. Standardised experimental
sampling design
c. The Irish ROV Holland I
Belgica
b
a
0
RESULTS
• ~126 000 m2 of seafloor were surveyed on and around Arc, Belgica and Logachev mounds.
• 2721 fish from 32 taxa were recorded. 27 species were found in coral habitat, 22 in 3D geogenic
structured habitat , 29 in fine sediment habitat.
• At the three study sites fine sediments were the most abundant habitat surveyed, followed by
coral and 3D geogenic structured habitat (Fig.2a)
• In contrast, fish were more abundant in the less frequently encountered coral and 3D geogenic
structured habitats (Fig.2b)
80
80
70
Average density ( SE)
(fish/1000 m2)
90
Percentage cover
70
60
50
50
100
n
20
Coelorinchus caelorhincus
135
Gadidae
10
Neocyttus helgae. Observed only on
coral habitat, slowly swimming on top of
framework
Paralepipidae
Lepidion eques . In coral habitat was observed
station holding and swimming next to isolated
corals and above thick coral framework. Station
holding fish have often been observed sheltering
behind boulders with respect to current direction.
9
Coelorinchus sp.1
14
Phycis blennoides
14
988
Lophius sp.
10
Anguilliformes
38
4
30
Centrophorus squamosus
4
20
Hoplostethus mediterraneus
10
10
Helicolenus dactylopterus
0
b. 0
40
30
40
Logachev
Belgica
Arc Mounds
Logachev
L
Group average
A
B
20
40
60
Similarity
LL
40
L
L
H.dactylopterus. Perched under coral bushes, on
top of coral, sitting on bottom next to corals.
When away from reef, it was almost always
associated with boulders or any structure
available.
Phycis blennoides. Often observed swimming
above coral framework or near the bottom in
Resemblance: S17 Bray Curtis
similarity
Belgica
2D Stress: 0.19
between coral bushes.
Habitat
Logachev
2d stress:
0.19
Resemblance: S17 Bray Curtis similarity
0
L
AA
B
B
L BL
LL
A
L L
B B B L
B A A
B
A A
A
A
B
A
B
A
A
Coral
3D structured
Fine sediment
85
Dalatias licha
11
Osmeriformes
5
25
Molva dypterigia
36
Micromesistius poutassou
30
Nezumia aequalis
125
Synaphobranchus kaupii
277
Deania calcea
3
Coryphaenoides sp.1
7
Rajidae
8
Trachyrincus sp.
8
B
Coral
28.F
31.C
18.F
22.F
21.F
16.F
14.F
14.C
14.3D
15.F
11.F
13.F
27.F
31.F
5.F
3.F
2.3D
8.F
9.C
6.F
8.C
32.C
9.3D
22.3D
31.3D
11.3D
13.C
11.C
6.3D
8.3D
5.3D
13.3D
3.3D
27.C
Mora moro
Chimaera monstrosa
40
B
2.C
18.3D
5
68
Molva dypterigia. When not in coral area, was often observed station
holding or resting on bottom associated with boulders.
21.C
115
Galeus melastomus
Similarity
80
27.3D
28
Conger conger
Belgica
• The ANalysis Of SIMilarity (ANOSIM) test performed among the three habitat categories showed
weak but significant fish assemblage differences ( Global R=0.25, p=0.1%). The post – hoc
comparison tests revealed highest differences between coral and fine sediment habitat (R=0.4)
and no differences between coral and 3D structured habitats (R=0).
• Cluster analysis and Multiple Dimensional Scaling showed differences in fish community structure
in relation to habitat type. Fish assemblages found in 3D geogenic structured and coral habitat
clustered together and were distinct from assemblages found on fine sediment samples.
• Analysis did not reveal significant location differences in fish composition
recorded
Resemblance: S17 Bray
Curtis similarityin coral and
3D geogenic structured habitat. Some regional differences in fish assemblages
recorded
at the
2D Stress:
0.19
Site
Arc Mounds
control sites were discernible however.
28.3D
80
Neocyttus helgae
Fig.2 Percentage coverage of each habitat type (a) and average fish density (b) at the three study sites
Similarity
60
Argentinidae
Arc Mounds
100
40
c.
Lepidion eques
60
20
a.
20
b.
3D structured
Fine sediment
Fig.4 Percentage of each species across the three habitats. n = number of individuals
observed.
Coloured squares highlight the main species driving the difference among habitats, as
identified by SIMPER analysis.
Samples
Coral + 3D structured
Fine sediment
Fig.3 Hierarchical clustering (a) and MDS plot (b) of 37 samples. Overlaying clusters (b) are defined at a 40% similarity level. L= Logachev Mounds ,
A = Arc Mounds, B = Belgica Mounds .
Chimaera monstrosa. Swimming above fine sediment.
Synaphobranchus kaupii . Drifting and swimming on large sandy areas
CONCLUSIONS
Our video surveys reveal that Irish coral reefs support a clear trend of higher abundance of fish than adjacent homogenous fine sediment areas.
Ice rafted boulders and drop stones, common on the upper continental margin, provide an important habitat for fish as suggested by the high co-occurrence of fish
associated with these features, particularly in areas of strong current.
The similarity of fish fauna in coral and 3D geogenic structured habitats, in both terms of density and species composition, suggests that these habitats are functionally
equivalent (Auster 2005), the main attracting factor being the physical structure itself (Harter et al., 2008). Both corals and boulders are an important source of habitat
complexity in relatively uniform deep sea areas and can provide an oasis of biodiversity and refuge for many deep sea fish. (Costello et al.,2005). Protection of these
habitats from destructive fishing should be implemented.
Analysis of ROV footage is a valuable instrument to describe deep-sea fish behaviour in situ and can give additional information on the association between fish and
surrounding habitat. Fig. 5 shows a tusk using a coral reef as an ambush point to prey on a smaller fish (probably Lepidion eques)
Fig.5 Brosme brosme preying on a smaller fish
REFERENCES
Auster P.J., 2005. Are deep-water corals important habitats for fishes? In: Freiwald A., Roberts J.M. (eds) Cold-water Corals and Ecosystems. Springer, Berlin Heidelberg, pp 761-769
Costello M.J., Mc. Crea M., Freiwald A., Lundalv T., Johnsson L., Bett B.J., van Weering T.C.E., de Haas H., Roberts J.M., Allen D., 2005. Role of cold water Lophelia pertusa coral reefs as fish habitat in the NE Atlantic. In: Freiwald A., Roberts J.M. (eds.) Cold-water Corals and Ecosystems. Springer, Berlin Heidelberg,
pp 771-805
Harter S.L., Ribera M.M., Shepard A.N., Reed J.K., 2009. Assessment of fish populations and habitat on Oculina Bank, a deep-sea coral marine protected area off eastern Florida. Fisheries Bulletin 107, 195-206
Kutti T.,Ragnrsson S.A., Beuck L., Fossa J.H., 2009. CoralFISH protocols for standardised fish census sampling strategies and methodologies,Deliverable D7,CoralFISH
AKNOWLEDGEMENTS
This research has received funding from the EU Seventh Framework Programme (FP7/2007-2013) under grant agreement nº 213144 and by the Department of Communications, Energy and Natural Resources under the Griffith Geoscience Research Awards (National Geoscience Programme 2007-2013). The views
and recommendations contained in this study reflect the views of the authors and do not necessarily reflect the views and opinions of the Minister for Communications, Energy and Natural Resources. The EC is not liable for any use that may be made of the information contained in this paper.