The effect of interannual variation in growth and condition on haddock recruitment

Abstract

Abstract:The relationship between recruitment and spawner biomass assumes that estimates of spawner biomass are proportional to total egg production by the stock. The validity of this assumption is in question for long-lived gadoid stocks; however, estimating total egg production independently of spawner biomass is seldom feasible. An alternative approach is to examine correlations between recruitment and variables likely to be proxies for total egg production by the stock. This indirect approach was used for haddock on the Scotian Shelf. Indices of growth (mean length at age-4) and condition (weight at 50 cm) were used as proxies for the reproductive potential of individual spawners. Both variables were positively correlated with recruitment over a 3-decade period . During the same time period, there was no relationship between recruitment and spawner biomass estimated by Virtual Population Analysis (VPA). This is further evidence that VPA-based spawner biomass is a poor index of the true reproductive potential of the stock. The results highlight the need to develop more accurate/precise measures of total egg production for use in recruitment research.Résumé : La relation entre le recrutement et la biomasse des géniteurs s'appuie sur la prémisse selon laquelle les estimations de la biomasse des géniteurs sont proportionnelles à la production totale d'oeufs par le stock. La validité de cette hypothèse est remise en question pour les stocks de gadoïdes à longue durée de vie. Toutefois, il est rarement possible d'estimer la production totale d'oeufs sans tenir compte de la biomasse des géniteurs. Une autre façon de procéder consiste à examiner les corrélations entre le recrutement et les variables considérées comme des approximations de la production totale d'oeufs par le stock. Cette approche indirecte a été appliquée au stock d'aiglefin de la plate-forme néo-écossaise. Des indices de la croissance (longueur moyenne à l'âge de 4 ans) et de la condition (poids à 50 cm) ont été utilisés comme approximations du potentiel reproducteur des géniteurs. Une corrélation positive entre ces variables et le recrutement a été observée sur une période de plus de 30 ans . Durant cette même période, aucune corrélation n'a été observée entre le recrutement et la biomasse des géniteurs estimée par analyse des populations virtuelles. Ces résultats démontrent une fois de plus que l'estimation de la biomasse des géniteurs par analyse des populations virtuelles ne reflète pas fidèlement le potentiel reproducteur d'un stock. Ils font également ressortir la nécessité d'élaborer des instruments de mesure plus justes et plus précis de la production totale d'oeufs à des fins d'utilisation dans le cadre de recherches sur le recrutement.[Traduit par la Rédaction] Marshall and Frank 355

Decreases in Condition and Fecundity of Freshwater Fishes in a Highly Polluted Reservoir

“…Raldúa et al (2007) reported more prevalence of liver pathologies in fish at sites with higher wholebody mercury concentrations. Our results support that the morphometric measurement of fish condition is a simple cost-effective measure of its well being, particularly because condition generally affects growth, reproduction and survival (Adams 1999;Marshall and Frank 1999). Although the fecundities observed in our study were within the ranges of other studies for the same species (Crivelli 1981;Vila-Gispert and Moreno-Amich 2000), we detected significantly low values at the impacted area for carp and pumpkinseed.…”

Spatial and temporal density dependence regulates the condition of central Baltic Sea clupeids: compelling evidence using an extensive international acoustic survey

“…As such, condition is a crucial parameter for the success of fish populations, since it may influence individual survival (Lambert and Dutil 2000), migration patterns (Slotte 1999), reproductive output (Blanchard et al 2003;Trippel and Neil 2004) and recruitment (Marshall and Frank 1999). Condition may be dependent on several, often interconnected, factors such as density dependence (Winters and Wheeler 1994), hydro-climatic conditions (Lloret and Rätz 2000), parasitic infection (Bagamian et al 2004) and selective fishing (Vainikka et al 2009).…”

Implementing Information on Stock Reproductive Potential in Fisheries Management: The Motivation, Challenges and Opportunities

“…r Positive associations between condition and recruitment have been observed for both demersal (Marshall & Frank 1999) and pelagic (Boyd et al 1998) stocks. r For Georges Bank haddock the fit of the S/R relationship was improved if estimates of spawning stock biomass excluded the first-time spawners (Wigley 1999 r For Northeast Arctic cod the total lipid energy in the livers of mature females showed a positive, linear correlation with recruitment over a 50-year time period (Marshall et al 2000).…”