Dynamics of the Georges Bank scallop fishery.
Date
1991
Authors
McGarvey, Richard.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The cyclical dynamics of the Georges Bank sea scallop fishery are investigated by time series and spatial data analysis, modelling, and dynamical hypothesis testing.
Surveys of Placopecten magellanicus, on Georges Bank, provided size-frequency distributions of the population from 1977 to 1988. Commercial time series of effort and catch, extending to 1944, corroborate the surveys. Population reproduction, early life history survival, and stock-recruitment interactions, within and between subareas along the clockwise direction of current flow, are computed.
Recruitment and egg production on the Northern Edge and Northeast Peak are correlated, suggesting a reproductively self-sustaining population. Large increases in stock-recruitment correlations were observed when the egg contribution of newly fecund scallops ages 3 and 4 was omitted from yearly totals which, together with physiological studies, suggests that scallops age 3 and 4 are not yet fully mature. Recruitment could be substantially enhanced by raising age of first capture.
Hypotheses for the 15-year cycle of Georges Bank scallops are threefold; periodic environmental forcing, Schaefer predator-prey, or Ricker density dependence. The fishery closely matches assumptions and mathematical features of the age-structured, stochastic-recruitment Schaefer model, comparing auto- and cross-correlations of recruitment, effort and stocksize from model and data. Population cycle hypothesis testing criteria are applied that are qualitative, and therefore robust.
Density dependence is implicated from age structure before compared with under exploitation. Due to a greatly shortened lifespan in the fishery, egg survivorship to age 2 is 300 times greater, estimated from survey, compared with a natural population, whose egg to recruit survival is deduced as the reciprocal of mean lifetime egg production.
Thesis (Ph.D.)--Dalhousie University (Canada), 1991.
Surveys of Placopecten magellanicus, on Georges Bank, provided size-frequency distributions of the population from 1977 to 1988. Commercial time series of effort and catch, extending to 1944, corroborate the surveys. Population reproduction, early life history survival, and stock-recruitment interactions, within and between subareas along the clockwise direction of current flow, are computed.
Recruitment and egg production on the Northern Edge and Northeast Peak are correlated, suggesting a reproductively self-sustaining population. Large increases in stock-recruitment correlations were observed when the egg contribution of newly fecund scallops ages 3 and 4 was omitted from yearly totals which, together with physiological studies, suggests that scallops age 3 and 4 are not yet fully mature. Recruitment could be substantially enhanced by raising age of first capture.
Hypotheses for the 15-year cycle of Georges Bank scallops are threefold; periodic environmental forcing, Schaefer predator-prey, or Ricker density dependence. The fishery closely matches assumptions and mathematical features of the age-structured, stochastic-recruitment Schaefer model, comparing auto- and cross-correlations of recruitment, effort and stocksize from model and data. Population cycle hypothesis testing criteria are applied that are qualitative, and therefore robust.
Density dependence is implicated from age structure before compared with under exploitation. Due to a greatly shortened lifespan in the fishery, egg survivorship to age 2 is 300 times greater, estimated from survey, compared with a natural population, whose egg to recruit survival is deduced as the reciprocal of mean lifetime egg production.
Thesis (Ph.D.)--Dalhousie University (Canada), 1991.
Keywords
Biology, Ecology., Biology, Oceanography., Agriculture, Fisheries and Aquaculture.