No abstract

No abstract

Evidence accumulated over the last decade indicates that reproductive potential of marine fish stocks is not correctly represented by spawning stock biomass. Fundamental variables that affect reproductive potential of fish stocks (i.e. proportion mature at age, fecundity, and offspring size and viability) have found to vary with age, size, and condition of spawning fish, and/or spawning experience. Modeling initiatives that attempt to describe reproductive potential by incorporating all available information on reproductive variables require extensive, high quality data of a temporal and spatial origin. In this study, we explored the influence of female age, size, and condition on several reproductive variables for the cod Gadus morhua, including maturity, fecundity, egg density and size, and larval size and growth. In addition, we described the potential for annual variation in these relationships to increase our knowledge of temporal stability for fundamental variables that influence reproductive potential.

Otolith shape analysis was examined to determine its utility for stock identification of haddock Melanogrammus aeglefinus on Georges Bank. Otolith samples were collected from the Northeast Peak (eastern Georges Bank) and the Great South Channel (western Georges Bank) spawning components to examine stock continuity across Georges Bank. Otolith shape was described using 20 Fourier harmonics, four morphometric characteristics (area, length, width, and perimeter), and two shape indices (circularity and rectangularity). Potential confounding sources of variation (fish length, otolith position, age‐group, and year‐class) were examined and accounted for in the analyses before interpretation of spatial/stock differences. Significant age‐specific differences in otolith shape between eastern and western Georges Bank haddock indicated stock separation across the Bank. Classification success for each spawning component ranged from 63 to 80% across age‐groups and appeared to depend on growth rate differences. Otolith shape analysis has potential for stock identification of haddock on Georges Bank, but only for year‐classes with differing growth rates. The results of this study indicated an underlying stock structure within the Georges Bank transboundary haddock resource that may assist in defining consistent stock definitions used by the United States and Canada.

No abstract

Epinephelus fuscoguttatus is widespread throughout the Indo-Pacific and features strongly in regional fisheries, including the live reef fish trade. We investigated age-specific demographic and reproductive characteristics of E. fuscoguttatus from the Great Barrier Reef, Australia, and examined implications for resource management. Age, growth, longevity, and the relationships between size or age and female sexual maturity and the recruitment of males into the study population were examined. Age validation using both oxytetracycline marking and edge-type analysis demonstrated that a single annulus formed each year. This grouper is long-lived (> 40 yr) and relatively slow-growing. The size and age distributions of the sexes strongly suggested protogynous hermaphroditism. Histological data suggested infrequent spawning in small mature females. Females contribute very little to reproductive output until about 566 mm fork length and 9 yr of age. Larger females make important reproductive contributions during their 30+ yr reproductive lifespan. Their relatively long lifespan, restriction of males to large size groups, and the disproportionate contribution of large females to reproduction have important implications for the harvest of E. fuscoguttatus. For example, current Queensland size regulations are poorly matched to the species' biology because they do not protect the reproductive elements of populations.

No abstract

No abstract