UCSC-SOE-11-10: Probable Values of Stock-Recruitment Steepness for North Pacific Albacore Tuna

Jon Brodziak, Hui-Hua Lee, Marc Mangel
03/28/2011 09:00 AM
Applied Mathematics & Statistics
We applied a new method to estimate probable values of stock-recruitment steepness for a Beverton-Holt recruitment curve for North Pacific albacore. We used information on growth, maturity at age, weight at length, natural mortality and reproductive ecology of albacore tuna and a simulation method to obtain the probability distribution of steepness. Thus, the results suggested that the North Pacific albacore tuna stock had a resilient to highly resilient stock‐recruitment relationship depending upon the choice of growth curve. The results also conformed to the expectation that faster somatic growth, as indicated by higher values of the von Bertalanffy k parameter, was associated with higher resilience in the stock‐recruitment relationship. Overall, the results indicated that the mean steepness of North Pacific albacore was less than unity. In this context, assuming that mean steepness is unity is a biologically implausible assumption because such an assumtpion implies that there is an infinite amount of compensation in the stock‐recruitment relationship.