TAILIEUCHUNG - Systematic bias in estimates of reproductive potential of an Atlantic cod (Gadus morhua) stock: implications for stock–recruit theory and management

When starting hormonal contraception after POEC (Levonelle 1500® or Levonelle One Step®) additional contraception should be advised until contraceptive efficacy is established (see Summary on page iv). There are no data on quick starting hormonal contraception after use of the emergency contraceptive, ulipristal acetate (UPA) (ellaOne®). As UPA is a progesterone receptor modulator that blocks the action of progesterone, it may affect the contraceptive efficacy of hormonal However, no interaction studies have been carried out to date. Therefore, the CEU have taken a pragmatic approach in developing its recommendations and these may be amended if new evidence becomes available | 980 Systematic bias in estimates of reproductive potential of an Atlantic cod Gadus morhua stock implications for stock-recruit theory and management C. Tara Marshall Coby L. Needle Anders Thorsen Olav Sigurd Kjesbu and Nathalia A. Yaragina Abstract Stock-recruit relationships that use spawning stock biomass SSB to represent reproductive potential assume that the proportion of SSB composed of females and the relative fecundity number of eggs produced per unit mass are both constant over time. To test these two assumptions female-only spawner biomass FSB and total egg production TEP were estimated for the Northeast Arctic stock of Atlantic cod Gadus morhua over a 56-year time period. The proportion of females FSB SSB varied between 24 and 68 and the variation was systematic with length such that SSB became more female-biased as the mean length of spawners increased. Relative fecundity of the stock TEP SSB varied between 115 and 355 eggs-g-1 and was significantly positively correlated with mean length of spawners. Both FSB and TEP gave a different interpretation of the recruitment response to reductions in stock size overcompensatory compared with that obtained using SSB either compensatory or depensatory . There was no difference between SSB and FSB in the assessment of stock status however in recent years 1980-2001 TEP fell below the threshold level at which recruitment becomes impaired more frequently than did SSB. This suggests that using SSB as a measure of stock reproductive potential could lead to overly optimistic assessments of stock status. Résumé Les relations stock-recrues qui utilisent la biomasse du stock reproducteur SSB pour representer le poten-tiel reproductif présupposent que la proportion de SSB représentée par les femelles et que la fecondite relative nombre d oeufs produits par unite de masse sont toutes deux invariables dans le temps. Afin d evaluer ces deux presuppositions nous avons estime la biomasse des reproducteurs femelles seuls FSB et .

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