The Extended Longevity of a Small Coral Reef Serranid; a Lesson from Cephalopholis Cyanostigma (Blue Spot Rock Cod) of the Central Great Barrier Reef, Australia (original) (raw)
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Aspects of the Growth and Natural Mortality of Exploited Coral Reef Fishes
1981
A newly developed computer-based method for the analysis of length-frequency data (ELEFAN I & II) is applied to data on reef fishes. It is shown that the growth of reef fishes often oscillates seasonally, and that adjusting for this effect considerably increases the accuracy of growth parameter estimates. This is also confirmed by a re-analysis of tagging data from the Caribbean. Potential causes of natural mortality in reef fishes are discussed in the light of a recently established empirical relationship between natural mortality, growth parameters and mean environmental temperature in fishes.
Inter-oceanic analysis of demographic variation in a widely distributed Indo-Pacific coral reef fish
Marine Ecology Progress Series, 2008
The surgeonfish Ctenochaetus striatus is abundant and widely distributed on reefs throughout the Indian and Pacific Oceans. Population samples at 15 sites that spanned 158°of longitude and 40°of latitude across both hemispheres of the Indian and Pacific oceans allowed us to examine geographic variation in longevity, growth rate and adult size of this species. Samples from 5 sites in the Indian Ocean, 6 in the western Pacific and 4 in the central Pacific provided otolith-based estimates of size-at-age for 1537 individuals. All populations displayed rapid growth to a distinct asymptotic size, a pattern characteristic of many acanthuroid fishes. In both oceans, fish lived longer at higher latitudes; in addition, Indian Ocean populations tended to be shorter-lived than those in the Pacific Ocean. In contrast, growth rate and adult size did not differ between the 2 oceans, and were not related to temperature (as a proxy for latitude) in either the Pacific or the Indian Ocean. Further, we found no relationship between fishing pressure and longevity, growth or adult size across our set of sampling sites, among which fishing pressure on this species varied from intense to zero. We hypothesize that (1) growth and adult size are most responsive to local environmental features unrelated to latitudinal (temperature) effects; and (2) variation in longevity reflects a combination of responses to latitudinal (temperature) gradients and as yet unidentified environmental differences between the Indian and Pacific oceans.
The purpose of this chapter is to consider the question “Is it necessary to validate the periodicity of increment formation in every species of fish for which we seek age-based demographic data”? The focus is on coral reef fishes. Four issues require consideration. Firstly, validation programs are expensive in terms of resources and time. This is especially important for coral reef fishes as resources available to tropical fisheries are often very limited. Secondly, many modern techniques used to validate the accuracy of age estimates require field and laboratory infrastructure that may not be available to fisheries laboratories serving coral reefs. Thirdly, the great majority of validation studies have confirmed the annual periodicity of increment formation. Fourthly, opportunities to study undisturbed populations of reef fishes from which reference age data can be derived are limited due to over-fishing and habitat alteration. We argue for a more strategic approach to age-based st...
Diversity
Patterns of age and growth of a sedentary damsel fish Acanthochromis polyacanthus were tested over a latitudinal range of approximately 10 degrees (1200 km) on the Great Barrier Reef (GBR), Australia. Within latitudes, these patterns were also compared on reefs in distance strata (inner, mid, and outer) across a continental shelf that ranged in width from 52 to 128 km. Although variation in length-max (SLMAX), growth, age-max (AMAX), and the von Bertalanffy metrics of Linf and K were found within and among latitudes, the greatest variation in some demographic characteristics was found among distance strata across the shelf regardless of latitude. Fish were always relatively smaller at inner shelf reefs and grew more slowly when compared to mid and outer shelf reefs; this was true regardless of the color morph of fish. The oldest fish collected was 11 years old, and there was no consistent variation in age-max among distances from shore. On outer reefs, there was a negative linear re...
Fisheries Research, 2000
The age, growth and mortality of Lutjanus carponotatus and L. vitta were determined from sectioned otoliths of ®shes from the central Great Barrier Reef. The periodicity of annulus formation was validated by oxytetracycline labelling of tagged ®shes in a separate study. Growth in length was variable between sexes for both species, males tending to grow larger than females. The von Bertalanffy growth function (fork length-at-age) for L. carponotatus was L t 313.0 (1Àexp {À0.449[t0.016]}), and L t 245.3 (1Àexp {À0.853[t0.179]}) for L. vitta. The oldest individuals found were an L. carponotatus individual of unknown sex, 20 years of age (FL335 mm) and a female L. vitta 12 years of age (FL257 mm). Otolith weight was strongly correlated with age for both species. The annual instantaneous rate of natural mortality (M) was estimated to be 0.199 for L. carponotatus and 0.342 for L. vitta, representing an annual survivorship of approximately 82 and 71%, respectively. The longer life span and lower rate of natural mortality for L. carponotatus indicates that this species will be more vulnerable to over®shing than L. vitta. #
Age-based analyses were used to demonstrate consistent differences in growth between populations of Acanthochromis polyacanthus (Pomacentridae) collected at three distance strata across the continental shelf (inner, mid-, and outer shelf ) of the central Great Barrier Reef (three reefs per distance stratum). Fish had significantly greater maximum lengths with increasing distance from shore, but fish from all distances reached approximately the same maximum age, indicating that growth is more rapid for fish found on outer-shelf reefs. Only one fish collected from inner-shelf reefs reached >100 mm SL, whereas 38−67% of fish collected from the outer shelf were >100 mm SL. The largest age class of adult-size fish collected from innerand mid-shelf locations comprised 3−4 year-olds, but shifted to 2-yearolds on outer-shelf reefs. Mortality schedules (Z and S) were similar irrespective of shelf position (inner shelf: 0.51 and 60.0%; mid-shelf: 0.48 and 61.8%; outer shelf: 0.43 and 65.1%, respectively). Age validation of captive fish indicated that growth increments are deposited annually, between the end of winter and early spring. The observed cross-shelf patterns in adult sizes and growth were unlikely to be a result of genetic differences between sample populations because all fish collected showed the same color pattern. It is likely that cross-shelf variation in quality and quantity of food, as well as in turbidity, are factors that contribute to the observed patterns of growth. Similar patterns of cross-shelf mortality indicate that predation rates varied little across the shelf. Our study cautions against pooling demographic parameters on broad spatial scales without consideration of the potential for cross-shelf variability.
2004
The growth, age, mortality rate and some aspects of the biology of a protogynous fish from the family Serranidae, Epinephelus merra Bloch, 1793, have been studied on the Réunion Island. This key species in the functioning of the Réunion coral reef ecosystem was sampled in a semi-artificial habitat. The log-transformed length-weight relationship was defined by: Ln(W) = 3.015 LT -1.970 and was not statistically different from that reported by other authors in natural habitats. Comparison between the total length of males and females revealed that sexual change occurred when fish were between 18 and 20 cm (TL), which corresponded to ages ranging from 3 to 5 years. A comparison between otolith reading methods for age assessment was done (in toto observations, assessment on digital photographs, and assessment by image analysis software). The von Bertalanffy growth curve provided low theorical maximum length (L∞ranging from 19.8 cm to 25.0 cm TL, depending on the method used) and relatively high growth rate (k ranging from 0.43 to 0.80, depending on the method used). Estimates of natural mortality (M) ranged from 0.90 to 1.67. These results could however be underestimated (L∞) or overestimated (k and M), possibly due to Lee's phenomenon linked to sampling which mainly focused on medium and large sizes. Implications for fishery management are discussed. SERRANIDAE OTOLITHES VALIDATION RÉTROCALCUL MILIEU SEMI-ARTIFICIEL RÉSUMÉ. -L'âge, la croissance, la mortalité et certains aspects de la biologie d'un Serranidae protogyne de l'île de La Réunion, Epinephelus merra Bloch, 1793, ont été étudiés. Cette espèce-clé dans le fonctionnement de l'écosystème corallien réunionnais a été récoltée en milieu semi artificiel, et a présenté une relation taillepoids (transformation Log) définie par : Ln(W) = 3,015 LT -1,970 qui n'est pas significativement différente de la relation en milieu naturel définie par d'autres auteurs. La comparaison des longueurs totales des mâles et des femelles a révélé que le changement de sexe se fait pour des tailles comprises entre 18 et 20 cm, ce qui correspond à des âges compris entre 3 et 5 ans. Une comparaison entre différentes méthodes d'évaluation de l'âge à partir des otolithes a été réalisée (lectures in toto, évaluations par lectures sur photos numérisées, et par logiciel d'analyse d'image). La courbe de croissance établie avec le modèle de von Bertalanffy a donné une longueur maximale théorique faible (L∞ entre 19,8 et 25,0 cm selon la méthode utilisée) et un taux de croissance assez fort (k compris entre 0,43 et 0,80 selon la méthode utilisée). Les estimations de la mortalité naturelle (M) ont fluctué entre 0,90 et 1,67. Ces résultats sont cependant peut-être sous-estimés (L∞) ou surestimés (k et M) de par un possible 'phénomène de Lee' lié à un échantillonnage centré sur des tailles moyennes et grandes. Les implications de ces résultats sur la gestion de l'espèce sont discutées.