Blanchard, JL, Maternal contribution to the reproductive potential of a recovering fish stock: variability in the fecundity and condition of haddock (Melanogrammus aeglefinus) on the Scotian Shelf (2000) [Masters Research]
Three years of fecundity data were collected over the period 1997-1999 for the Eastern Scotian Shelf haddock and data were also collected for the neighbouring, Southwest Scotian Shelf haddock stock in 1998 and 1999. Fecundity-body size relationships were determined for the three years of data collected and were highly variable compared to the neighbouring southwestern Scotian Shelf stock. Significant inter-annual differences in the intercepts of these relationships were observed over the 1997-1999 period and appeared to be reflective of inter-annual differences in condition. Relative to other haddock stocks throughout the North Atlantic, ESS haddock exhibited the lowest and most variable fecundity-length relationship.
Multiple regression models incorporating length and condition were developed using three different measures of condition: liver index (H.S.I.); Fultonís condition index (K) and length specific weight (with a length*weight interaction term). All measures of condition contributed to explaining additional variation in fecundity-at-length (from 15- 19%). H.S.I. explained the most variation, followed by length specific weight, then Fultonís K.
The stock reproductive potential was reconstructed for a two decade period (1979-1999) by incorporating the fecundity equations into a length based population model. This yielded annual estimates of Total Egg Production (TEP). Results showed that TEP has declined over that period with evidence of a recent increase in 1999. The decline was more drastic when TEP was separated for repeat spawners (fish above 40.5 cm). Also, there appeared to be a stronger relationship between TEP by repeat spawners and recruitment than the relationship between VPA-based SSB.The TEP estimates based on repeat spawners are more representative of the quantitative and qualitative factors contributing to reproductive potential and hence this approach is a more accurate method of estimating recruitment.
|Item Type:||Masters Research|
|Keywords:||fecundity, haddock, Scotian Shelf, population dynamics|
|Research Division:||Biological Sciences|
|Research Field:||Population Ecology|
|Objective Group:||Ecosystem Assessment and Management|
|Objective Field:||Ecosystem Assessment and Management of Marine Environments|
|Author:||Blanchard, JL (Dr Julia Blanchard)|
|Deposited By:||Sustainable Marine Research Collaboration|
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