International eel symposium, 2003 - Quebec August 11, 2003
Oral Presentation

Development of Conservation Reference Points for the American Eel from a Stochastic Life Table Model

Cairns, D.K.* Department of Fisheries and Oceans, Box 1236, Charlottetown, PEI Canada C1A 7M8 cairnsd@dfo-mpo.gc.ca
Chaput, G.J. Department of Fisheries and Oceans, Box 5030, Moncton, NB Canada E1C 9B6 chaputg@dfo-mpo.gc.ca..

Presenter email address: cairnsd AT dfo-mpo.gc.ca

Abstract Text: A life table model in which growth is randomly varied, and in which natural mortality, fishing mortality, and maturity schedules depend on size, was prepared for the American eel (Anguilla rostrata). The model was fitted to length frequency and length-at-age data from Prince Edward Island in the southern Gulf of St. Lawrence. Eels sampled from an unexploited estuary were larger than those from exploited estuaries and from the same estuary in 1973, when it was commercially exploited. Rates of natural mortality and emigration were adjusted in the model until simulated length frequencies matched those from the unexploited population. A fishing mortality of 0.6 produced length frequencies similar to those from exploited estuaries, which suggests that fishing mortality in the PEI eel fishery is 0.6. Inter-annual variation of recruitment strength in modelled populations produced highly variable length frequency distributions for small eels, but had limited effect on length frequency distributions of eels over 50 cm. Conservation reference points can be based on targets or limits to the reduction in spawner escapement caused by fishing mortality. Fishing mortality estimated for Prince Edward Island (0.6) reduced egg deposition by 79-83%, a reduction which exceeds both target (50%) and limit (70%) conservation reference points.