Phase 2

Possible evidence for long-term shifts in the feeding preferences of North Sea fish over the past 100 years.

Cefas scientists and their predecessors in the Ministry of Agriculture, Fisheries & Food (MAFF) have been collecting information on fish feeding preferences since the laboratory in Lowestoft was first established in 1903. With the imminent closure of the existing facilities in Lowestoft, efforts are underway to digitise historic information as a matter of urgency. An online, searchable database of historic fish stomach content records has been constructed (www.cefas.co.uk/dapstom) and it has become apparent that data are available throughout the last century, and that these might indicate significant long-term changes in marine ecosystem functioning. However additional funding is required to continue digitisation of paper records, and particularly to incorporate those data from the earliest period, 1902-1906.

Figure 1. The research vessel “RV Huxley”. This former steam trawler was commissioned in 1902 to assist with the research work of the newly created fisheries laboratory in Lowestoft.

Cruises of the Research Vessel ‘Huxley’

In 1902 the steam trawler ‘Huxley’ (figure 1) was requisitioned by the Marine Biological Association, in order to carry out fishery investigations as part of UK commitments under the fledgling International Council for the Exploration of the Seas (ICES). Detailed information was collected on fish abundance, size and movement patterns (Garstang 1905). Information was also collected on the ‘food of fishes’. These data were published by Todd in 1905 and 1907, and represent a very useful early resource for those hoping to reconstruct how foodwebs in the North Sea might have changed as a result of intensive fishing and/or climate change over the past 100 years.

There have been considerable variations in the catch of commercial fish species in the North Sea over the past century (figure 2), and many species are currently experiencing their lowest ever population levels following a century (or perhaps more than 1000 years, see Barrett et al. 2004) of intensive exploitation. Some species (such as herring) have experienced complete stock collapses and recovery over the 100 year period, whereas many gadoid species (cod, whiting and haddock) experienced a ‘boom’ in population numbers during the 1960s and 1970s but have subsequently declined. These marked changes in fish biomass, and concomitant changes in the benthic biota (see Callaway et al. 2007), will be reflected in the 100 year time-series of fish diet information.

Figure 2. Total international landings of commercial fish (in metric tonnes) from the North Sea between 1892 and 2005.

Uniqueness of the data

Many authors (notably Pope & Macer 1996; Christensen et al 2003) have speculated about possible long-term changes in marine food-webs as a result of fishing and climate, however very little ‘hard data’ has been available to confirm or refute such speculations. Some authors

have examined changes in the stable isotope composition of materials held in museums, to deduce long-term changes in the diets of particular species, indeed Wainwright et al. (1993) suggested a long-term change in the diet of haddock on the Grand Banks over the twentieth century, whereas Thompson et al. (1995) suggested a change in the diets of fulmars around Shetland. However, this technique does not provide a picture of what has really changed in the ecosystem. Such information can only be gained by detailed examination of stomach contents.

No other fisheries laboratory anywhere in the world has been collecting information on fish feeding preferences on a continual basis as long as the MAFF/Cefas laboratory in Lowestoft. When it is completed the DAPSTOM database will represent a unique resource of great utility for future ecosystem modelling efforts throughout Europe.

References

Christensen C., Guénette S., Heymans J.J., Walters C.J., Watson R., Zeller D., Pauly D. (2003) Hundred-year decline of North Atlantic predatory fishes. Fish and Fisheries 4, 1–24.

Barrett JH, Locker AM, Roberts CM (2004) The origins of intensive marine fishing in medieval Europe: the English evidence. Proc R Soc Lond B 271:2417–2421.

Callaway R., Engelhard G.H., Dann J., Cotter J. and Rumohr H. (2007) A century of North Sea epibenthos and trawling: comparison between 1902-1912, 1982-1985 and 2000. Marine Ecology Progress Series 346: 27-43.

Garstang, W. (1905). Report on the trawling investigations, 1902-3, with especial reference to the distribution of the plaice. First Report on Fishery and hydrographic investigations in the North Sea and adjacent waters (southern area), International Fisheries Investigations, Marine Biological Association, UK, 67–198.

Pope, J.G., Macer, C.T.(1996) An evaluation of the stock structure of North Sea cod, haddock, and whiting since 1920, together with a consideration of the impacts of fisheries and predation effects on their biomass and recruitment. ICES Journal of Marine Science, 53:1157-1169

Thompson, D.R., Furness, R.W., Lewis, S.A. (1995) Diets and long-term changes in d15N and d13C values in northern fulmars. Fulmarus glacialis from two northeast Atlantic colonies. Marine Ecology-Progress Series, 125: 3-11.

Todd, R.A., 1905. Report on the food of fishes collected during 1903. Rep. North Sea Fish. Invest. Comm. 1, pp. 227–287.

Todd, R. A. 1907. Second report on the food of fishes (North Sea, 1904–1905). Mar. Biol. Ass. U.K., Second Rep. on Fish. and Hydr. Inv. in the North Sea and adjacent waters (Southern Area), 1904–1905, I: 49–164.

Wainright SC, Fogerty MJ, Greenfield RC, Fry B (1993) Longterm changes in the Georges Bank food web: trends in stable isotopic compositions of fish scales. Marine Biology, 115: 481-493.