Fishing down Canadian aquatic food webs

The mean trophic level (TL) of fish landed in fisheries on the east and west coasts of Canada is declining by 0.03–0.10·decade–1, similar to global trends. This finding is based on data from United Nations Food and Agriculture Organization and the Canadian Department of Fisheries and Oceans and other Canadian sources for the period 1873–1997. Significant rates of decline in mean TL were obtained even when key species — Atlantic cod (Gadus morhua) on the east coast and Pacific herring (Clupea pallasi) and Pacific hake (Merluccius productus) on the west coast — were omitted from the analysis. Fish taken in inland water fisheries did not exhibit a decline in mean TL. Two models were developed, based on length and age, respectively, for correcting TL estimates of individual species for the effects of changes in body size due to changes in fishing mortality. Both produced corrections that were small relative to changes in mean TL that resulted from changes in species composition of the catch over time. Overall...

[1]  Charles F. Cole,et al.  Sustaining Marine Fisheries , 2000 .

[2]  E. Cortés.  Standardized diet compositions and trophic levels of sharks , 1999 .

[3]  J. Csirke,et al.  How Pervasive is "Fishing Down Marine Food Webs"? , 1998 .

[4]  D. Pauly,et al.  How Pervasive Is 'Fishing Down Marine Food Webs'? , 1998, Science.

[5]  S. Jennings,et al.  Life history correlates of responses to fisheries exploitation , 1998, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[6]  D. Pauly,et al.  Fishing down marine food webs , 1998, Science.

[7]  John F. Caddy.  A short review of precautionary reference points and some proposals for their use in data-poor situations , 1998 .

[8]  D. Pauly,et al.  Cross-Validation of Trophic Level Estimates from a Mass-Balance Model of Prince William Sound Using 15N/14N Data , 1998 .

[9]  T. Parsons.  The Impact of Industrial Fisheries on the Trophic Structure of Marine Ecosystems , 1996 .

[10]  D. Pauly.  Anecdotes and the shifting baseline syndrome of fisheries. , 1995, Trends in ecology & evolution.

[11]  D. Pauly,et al.  Primary production required to sustain global fisheries , 1995, Nature.

[12]  Robert M. May,et al.  Large-Scale Ecology and Conservation Biology. , 1995 .

[13]  J. Beddington,et al.  Harvesting species of different lifespans. , 1994 .

[14]  Edward L. Mills,et al.  Exotic Species in the Great Lakes: A History of Biotic Crises and Anthropogenic Introductions , 1993 .

[15]  Villy Christensen,et al.  ECOPATH II − a software for balancing steady-state ecosystem models and calculating network characteristics , 1992 .

[16]  G. Fleischer.  Status of coregonine fishes in the Laurentian Great Lakes , 1992 .

[17]  A. Campbell,et al.  Natural diets of lobster Homarus americanus from barren ground and macroalgal habitats off southwestern Nova Scotia, Canada , 1987 .

[18]  R. Myers,et al.  Predicting Natural Mortality Rates and Reproduction–Mortality Trade-offs from Fish Life History Data , 1983 .

[19]  G. Hewes.  Indian Fisheries Productivity in Pre-Contact Times In the Pacific Salmon Area , 1973 .

[20]  M. Webber,et al.  Marine Mammals of the World , 1972 .

[21]  S. Groot.  On the interrelationships between morphology of the alimentary tract, food and feeding behaviour in flatfishes (pisces: pleuronectiformes) , 1971 .

[22]  M. Culley.  The Pilchard; biology and exploitation , 1971 .

[23]  L. Walford,et al.  The British Columbia Fisheries , 1945 .