Variation in reproductive parameters of Plectropomus leopardus populations between coral reefs open and closed to fishing was examined in two geographic regions (off Townsville (19°S) and in the Swains (22°S)) of the Great Barrier Reef, Australia. The reproductive parameters that were examined included the operational (reproductive) sex ratio and size and age structure of mature females, sex-changing individuals (transitionals), and mature males. There was a greater proportion of males above the minimum size and age of harvest on reefs closed to fishing for 8-10 years than on reefs open to fishing, although the effect varied with geographic region. Nevertheless, neither the sex ratio, mean age, nor mean size of males or transitionals varied significantly with reef closure status. Females, however, were significantly older and larger on closed than on open reefs in both regions. Marked regional variations in the sex ratio and average age of transitionals were found independent of reef closure status, suggesting regional variation in reproductive strategies. Controlled manipulations, inclusion of broad spatial scales, and detailed studies of intra- and inter-specific variation in serranid reproductive biology are necessary to resolve such complexities in the responses of protogynous serranids to fishing pressure and management strategies.

No abstract

The gonadal ontogeny through sex differentiation and transition of three protogynous coral trout species, Plectropomus leopardus, P. maculatus and P. laevis was described, based on anatomical and germinal differences along the length of the reproductive tract. Gonads of immature and mature females, sex changing individuals (transitionals) and males were examined. Specific anatomical features that were compared between sexual phases included the presence and structure of sperm sinuses, gonadal musculature and germinal cell types. All three coral trout species first differentiated as an immature female. The sexual pattern of P. leopardus and P. maculatus was concluded to be diandric protogynous hermaphroditism (males were derived from the juvenile phase as well as through sex change of mature females). Plectropomus laevis was found to be monandric as males were only derived through sex change in mature females. Structural changes did not occur concomitantly with the germinal changes associated with sex change in these Plectropomus species, which is atypical for protogynous species described to date. Precursory sperm sinuses in the dorso‐medial region of the gonad were present, although non‐functional, in a proportion of immature and mature females of all three species. These proportions, however, varied between species depending on the sexual pattern. The structural and germinal changes observed were hypothesized as anatomical adaptations that aid in minimizing time spent in the (non‐reproductive) sexual transition phase and maximizing flexibility in male development in the diandric species.

Species in the coral trout complex Plectropomus spp. are some of the most desired and exploited in the Indo-Pacific, although data are limited for most species. Demographic parameters of blue-spot coral trout, Plectropomus laevis, were estimated on the basis of specimens collected from five regions of the Great Barrier Reef and Torres Strait, Australia, between 1995 and 2005 to define demography and population status over a broad range. In total, 1249 individuals were collected to estimate growth, mortality and reproductive parameters. Growth parameters based on the von Bertalanffy model were K = 0.096 year–1, L∞ = 1159 mm fork length (FL) and the best-fit model suggested non-asymptotic growth over the size and age ranges represented in the sample. Maximum age was 16 years, total mortality was estimated at 0.39 (±0.031), and estimated size and age at first maturity were 299 mm FL (range: 299–872) and at 1 year (range: 1–6.5), respectively, with the size range over which sex change occurred at 460–872 mm FL. Population parameters and available relative abundance estimates indicated that long-term sustainable harvest rates of P. laevis will be lower than those for P. leopardus and species-specific size-based management measures are necessary to ensure the species is not overfished.

We investigate the use of multivariate life-history indices to assess the performance of no-take zones with respect to ameliorating the impacts of harvest on exploited coral reef fish populations in the Great Barrier Reef Marine Park. A range of life-history parameters were estimated for the two major target species of the Great Barrier Reef (GBR) line fishery, common coral trout (Plectropomus leopardus) and red throat emperor (Lethrinus miniatus), collected from five adjacent reefs (three of which were closed to all forms of fishing) in each of three geographically dispersed regions between 1995 and 1998. Life-history parameters were used to compare the status of populations on open and closed reefs over regions and years. Principal components (PC) analyses were used to effectively reduce the number of parameters to four significant PCs for each species, accounting for 84% and 94% of the total variation in the data for common coral trout and red throat emperor, respectively. We were able to clearly identify those populations that were sampled from reefs open or closed to fishing based on the multivariate descriptors of life-history parameters. The concurrent use of several life-history indices maximised our potential to differentiate changes related to no-take zones from background variation.Résumé : Nous examinons l'utilisation des indices démographiques multidimensionnels pour évaluer la performance des zones de protection marines (MPA) établies pour atténuer l'impact de la récolte sur les populations de poissons des récifs coralliens dans le parc marin de la Grande Barrière de Corail. Nous avons estimé un nombre de variables démographiques pour les deux espèces qui sont le plus couramment ciblées par la pêche à la ligne sur la Grande Barrière de Corail (GBR), la loche saumonée (Plectropomus leopardus) et l'empereur gueule longue (Lethrinus miniatus), récoltées sur cinq récifs adjacents (dont trois où toute forme de pêche est interdite) dans chacune de trois régions séparées géographiquement de 1995 à 1998. Les variables démographiques ont servi à comparer l'état des populations dans les récifs protégés et non protégés au cours des années dans les différentes régions. Des analyses des composantes principales (PC) ont permis de réduire le nombre de variables à quatre PC significatives pour chaque espèce, expliquant ainsi respectivement 84 % et 94 % de la variation totale des données pour la loche saumonée et l'empereur gueule longue. Les descripteurs multidimensionnels des variables démographiques nous ont permis de distinguer clairement les populations échantillonnées sur les récifs protégés et sur les récifs non protégés. L'utilisation conjointe de plusieurs indices démographiques a maximisé notre capacité de reconnaître les changements dus à la présence des MPA de la variation sous-jacente.[Traduit par la Rédaction] Begg et al. 692