7 ToR d Developing EcoQO on changes in the proportion of large fish
7.5 Concluding comments
Analyses undertaken for the OSPAR QSR raised two interesting issues. First, the proportion of large fish indicator varies spatially across the North Sea, with a pattern that was persistent over time despite major changes in exploitation rates and consid‐
erable variation in the overall regional scale North Sea indicator value. The resulting regional scale temporal variation in the indicator may need to be taken into account when formulating management advice, and may require some form of spatial resolu‐
tion to be applied in the size‐resolved multispecies modelling work that is currently in progress. The second issue, in respect of metric redundancy, established that the proportion of large fish indicator provides relatively specific information regarding changes in the overall composition, structure and function of demersal fish communi‐
ties. To ensure that the range of aspects of change in fish communities likely to be of policy interest is covered, such as biodiversity, additional surveillance metrics will need to be applied.
This second issue was examined formally in a new analysis performed by WGECO.
Examination of species richness and species evenness among the larger fish compo‐
nent of the North Sea demersal fish community suggested that biodiversity in the community was also improving, alongside the increase in the proportion of large fish.
Finally, the trajectory, in terms of the biomass of fish of both ≤40 cm and >40 cm in length considered independently, was examined. This helped to elucidate how the community had changed, giving rise to the observed trend in the proportion of large fish indicator. This empirical analysis helps in understanding the behaviour of the indicator and should inform the ongoing modelling work.
7.6 References
Andersen, K. H., and Beyer, J. E. 2006. Asymptotic size determines species abundance in the marine size spectrum. The American Naturalist, 168: 54–61.
Andersen, K.H., and Pedersen, M. 2009. Trophic cascades in marine ecosystems driven by fish‐
ing and primary productivity. Submitted.
Andersen, K.P., and Ursin, E. 1977. A multispecies extension to the Beverton and Holt theory of fishing, with accounts of phosphorus circulation and primary production. Meddelelser fra Danmarks Fiskeri‐Og Havundersogelser,VII, 319–435.
Caldarelli, G., Higgs, P.G., and McKane, A.J. 1998. Modelling coevolution in multispecies communities. Journal of Theoretical Biology, 193:345–358.
Daan, N., Bromley, P. J., Hislop, J. R. G., and Nielsen, N. A. 1990. Ecology of North Sea fish.
Netherlands Journal of Sea Research, 26:343–386.
Floeter, J., and Temming, A. 2003. Explaining diet composition of North Sea cod (Gadus mor‐
hua): prey size preference vs. prey availability. Canadian Journal of Fisheries and Aquatic Sciences, 60:140–150.
Floeter, J., and Temming, A. 2005. Analysis of prey size preference of North Sea whiting, saithe and grey gurnard. ICES Journal of Marine Science, 62:897–907.
Fraser, H. M., Greenstreet, S. P. R., Fryer, R. J., and Piet, G. J. 2008. Mapping spatial variation in demersal fish species diversity and composition in the North Sea: accounting for species‐
and size‐related catchability in survey trawls. ICES Journal of Marine Science, 65:531–538.
Fraser, H. M., Greenstreet, S. P. R., and Piet, G. J. 2007. Taking account of catchability in groundfish survey trawls: implications for estimating demersal fish biomass. ICES Journal of Marine Science, 64:1800–1819.
Greenstreet, S. P. R., and Hall, S. J. 1996. Fishing and the ground‐fish assemblage structure in the northwestern North Sea: an analysis of long‐term and spatial trends. Journal of Animal Ecology, 65:577–598.
Greenstreet, S. P. R., and Rogers, S. I. 2006. Indicators of the health of the fish community of the North Sea: identifying reference levels for an Ecosystem Approach to Management. ICES Journal of Marine Science, 63:573–593.
Greenstreet, S. P. R., Spence, F. E., and McMillan, J. A. 1999. Fishing effects in Northeast Atlan‐
tic shelf seas: patterns in fishing effort, diversity and community structure. V. Changes in structure of the North Sea groundfish assemblage between 1925 and 1996. Fisheries Re‐
search, 40:153–183.
Guirey, E., Speirs, D., Gurney, W., Heath, M., and Greenstreet, S. 2008. A new multispecies, physiologically structured fish ecosystem model. ICES CM2008/F:04.
Gurney, W., Tyldesley, G., Wood, S., Bacon P., Heath, M., Youngson A., and Ibbotson A. 2007.
Modelling length at age variability under irreversible growth. Canadian Journal of Fisher‐
ies and Aquatic Sciences, 64:638–653.
Hall, S. J., Collie, J. S., Duplisea, D. E., Jennings, S., Bravington, M., and Link, J. 2006. A length‐
based multispecies model for evaluating community responses to fishing. Canadian Jour‐
nal of Fisheries and Aquatic Sciences, 63: 1344–1359.
Heath, M. 2009. End‐to‐end foodweb analysis as the basis for ecosystem advice on impacts of fishing. Invited oral presentation at ʺDeveloping IMBER Science in the UKʺ, Plymouth, January 2009. http://www.imber‐uk.org/presentations/heath.pdf.
Heslenfeld, P., and Enserink, L. 2008. OSPAR Ecological Quality Objectives: health indicators for the North Sea. ICES Journal of Marine Science, 65: 000–000.
ICES. 1994. Report of the Working Group on Ecosystem Effects of Fishing Activities. ICES Document, CM1994/Assess/Env:1.
ICES. 1995. Report of the Study Group on Ecosystem Effects of Fishing Activities. ICES Coop‐
erative Research Report, 200, 120pp.
ICES. 1996. Report of the Working Group on Ecosystem Effects of Fishing Activities. ICES Document, CM1996/Assess/Env:1/G.
ICES 2001. Report of the ICES Advisory Committee on Ecosystems. ICES Cooperative Research Report, 249, 75.
ICES 2007. Report of the Working Group on Ecosystem Effects of Fishing Activities (WGECO).
Copenhagen, Denmark, ICES.
ICES 2008. Report of the Working Group on Ecosystem Effects of Fishing Activities (WGECO).
Copenhagen, Denmark, ICES.
ICES 2008, Report of the Working Group on Fish Ecology (WGFE). ICES CM 2008/LRC:04.
Jennings, S., Greenstreet, S. P. R., and Reynolds, J. 1999. Structural change in an exploited fish community: a consequence of differential fishing effects on species with contrasting life histories. Journal of Animal Ecology, 68:617–627.
Pedersen, M., Andersen, K.A., Beyer, J., and Lundberg, P. 2009. Assembly of aquatic communi‐
ties from size‐structured species populations. Submitted.
Piet, G. J., and Jennings, S. 2005. Response of potential fish community indicators to fishing.
ICES Journal of Marine Science, 62:214–225.
Pope, J. G., Rice, J. C., Daan, N., Jennings, S., and Gislason, H. 2006. Modelling an exploited marine fish community with 15 parameters – results from a simple size‐based model. ICES Journal of Marine Science, 63: 1029–1044.
Rossberg, A. G., Ishii, R., Amemiya, T., and Itoh, K. 2008. The top–down mechanism for body‐
mass–abundance scaling. Ecology, 89:567–580.
Rossberg, A. G., Bränström, Å., and Dieckmann, U. 2009. How trophic interaction strength depends on traits‐A conceptual framework for representing multidimensional trophic niche spaces. Theoretical Ecology, in press.
Underwood, A. J., Chapman, M. G., and Crowe, T. P. 2004. Identifying and understanding eco‐
logical preferences for habitat or prey. Journal of Experimental Marine Biology and Ecol‐
ogy, 300:161–187.
Ursin, E. 1973. On the prey size preferences of cod and dab. Danmarks Fiskeri og Havunderso‐
gelser, 7:85–98.
8 ToR e Prioritizing fish species for research on fishing mortality