Histological analysis invalidates macroscopically determined maturity ogives of the Kattegat cod (Gadus morhua) and suggests new proxies for estimating maturity status of individual fish

Abstract

M. 2006. Histological analysis invalidates macroscopically determined maturity ogives of the Kattegat cod (Gadus morhua) and suggests new proxies for estimating maturity status of individual fish. e ICES Journal of Marine Science, 63: 485e492.Assessment and management of fish populations currently rely on correct estimation of the spawning-stock biomass (SSB), which is based on accurate maturity ogives of the population. Although maturity ogives are usually calculated through macroscopic evaluation of the gonads, histology is generally considered to be more accurate. Here we show that the macroscopic analysis consistently overestimates the proportion of mature females for all age classes in Kattegat cod. The resulting bias showed minimum values for all age classes about a month before the spawning season. Consequently, estimation of the incidence of maturation in females several months before or after the spawning season can only be accurate using histological techniques. Further, the observed bias was used to reconstruct a historical data set of maturity ogives of Kattegat cod. The results showed that female spawning biomass (FSB) might have been overestimated by up to 35%. However, as histological analysis is considered a laborious procedure, proxies of maturity status were sought. It was indicated that the gonadosomatic and hepatosomatic indices may serve as robust proxies for discriminating mature females from immature, thus greatly enhancing the accuracy of the macroscopic maturity evaluation of cod gonads when histological analysis is lacking.

Migratory behaviour of Atlantic cod Gadus morhua: natal homing is the prime stock-separating mechanism

“…For retained fish that had not been gutted, gonadal inspection was conducted. Sexual maturity of each cod was classified according to a 4-stage macroscopic scale, used in the International Bottom Trawl Survey (IBTS; Vitale et al 2006); a more detailed histological analysis was not possible because most of the fish had been deep frozen before being delivered to the laboratory. Fish in Stages 1 and 2 were considered as non-maturing, whereas fish in Stages 3 and 4 were considered as maturing or mature.…”

Changes in size at maturity of European hake Atlantic populations in relation with stock structure and environmental regimes

“…Those ogives are usually calculated from a macroscopic evaluation of the gonad maturity. However, macroscopic analysis may overestimate the proportion of mature females (Murua et al, 2003;Vitale et al, 2006).. Moreover, in most scientific assessments of European marine fish stocks, SSB is calculated using a fixed maturity ogive, ignoring the inter-annual variability in this parameter.…”

Rapid Reproductive Analysis and Length–Weight Relation for Blacktail Snapper, <I>Lutjanus Fulvus</I> (Actinopterygii: Perciformes: Lutjanidae), from a Remote Village in Papua New Guinea

“…Because macroscopic gonad classification systems are known to introduce excessive error when describing reproductive parameters (Vitale et al 2006, Longenecker et al 2013, we evaluated our accuracy in determining sex and reproductive status by macroscopic examination. We misclassified 43% of specimens examined (could not determine sex, 8.8%; incorrect sex, 4.4%; incorrect status, 20.2%; incorrect sex and status, 9.6%).…”