Publication Abstract

Effects of Condition on fecundity andtotal egg production of eastern Scotian Shelf haddock (Melanogrammus aeglefinus).

J.L Blanchard, K.T. Frank, J.E. Simon

A fecundity study of the eastern Scotian Shelf haddock (Melanogrammus aeglefinus) stockduring the 19971999 spawning seasons is reported. We developed a model that accounted forfecundity changes at the individual level and that could be used to estimate populationegg production beyond the study period. Incorporating condition factors into the model(relative condition factor (Kn) and hepatosomatic index) accounted for a significantproportion of the residual variation. The model predicted that a change in Kn from 0.8 to1.0 resulted in a twofold increase in fecundity at length. This variability was as greatas that observed for fecundity-length relationships among stocks. Three time series(1979-2001) of total egg production (TEP) were constructed using different fecundityrelationships: one with a condition effect, one based on length only, and one based onweight only. The magnitude of change in TEP resulting from the condition effect rangedfrom +30 to -20%. Condition effects during the first half of the time series resulted inan enhancement of TEP, whereas in the latter half, condition effects depressed TEP Thisevaluation of TEP generated new insights into haddock stock dynamics but did not result ina dramatic improvement of the relationship between recruitment and stock reproductivepotential.

Reference:

J.L Blanchard, K.T. Frank, J.E. Simon 2003. Effects of Condition on fecundity and totalegg production of eastern Scotian Shelf haddock (Melanogrammus aeglefinus) CanadianJournal of Fisheries and Aquatic Sciences 60 (3) 321-332