Research Document - 2000/028

An examination of the possible effect of spawning stock characteristics on recruitment in 4 Newfoundland groundfish stocks.

By M.J. Morgan, P.A. Shelton, D.E. Stansbury, J. Brattey, and G.R. Lilly

Abstract

Several characteristic of the spawning stock biomass of 3LNO American plaice, 2J3KL cod, 3NO cod and 3Ps cod were explored for variability and for relationships with the residuals from Beverton-Holt stock-recruit models. Weighted mean age of the SSB, proportion of first time spawners and proportion female all show substantial variation over the time period. The residuals from the stock-recruit relationship show a tendency to increase with mean age of the SSB for 3LNO American plaice and 2J3KL cod, indicating that recruitment is over estimated when mean age is low. The residuals tend to increase with proportion of first time spawners for 3NO cod and perhaps 3LNO American plaice and 3Ps cod, indicating that recruitment is over estimated when the proportion of first time spawners is low. For 3LNO American plaice, 3NO cod and 3Ps cod there is a tendency for the residuals from the Beverton-Holt fits to increase as proportion female increases indicating that recruitment is under estimated when proportion female is high.

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