The lipid content and fatty acid composition of the small common wrasse Symphodus ocellatus was analysed within two populations located in very different biotopes on the French shore: a Caulerpa ...taxifolia meadow located in Cap Martin and a Posidonia oceanica bed located in Villefranche. Polar lipids represented 82-90% of the total lipid in adult female livers, gonads and in eggs. Cholesterol in gonads and eggs and triacylglycerols in livers were the dominant neutral lipids. Differences in lipid classes were found in livers between the two populations, but not in their gonads and eggs. Moreover, a quantitative difference in total lipid content was evident. Young fish living on the C. taxifolia meadow in winter had 21% less lipid than those living on the P. oceanica bed. The populations of S. ocellatus showed differences between triacylglycerol versus phospholipid fatty acid compositions and between gonad versus liver fatty acid compositions. Moreover, a significant difference was found between both populations in their liver triacylglycerol fatty acid compositions, suggesting a difference in diet. Gut content analysis supported this hypothesis as it showed important differences in the ingested preys between the two populations in January (planktonic vs. benthic, frequency of isopods) and in June (frequency of gastropods). Thus, we found that the fish populations from Villefranche and Cap Martin showed significant differences in body lipids due to different nutritional habits.PUBLICATION ABSTRACT
Physical factors influencing the distribution and abundance of seven common labrid fishes were examined over four rocky reef locations in northeastern New Zealand. Depth and exposure for each species ...(both within and among sexes) were related to pectoral fin aspect ratio. Each of the four locations (two mainland and two island) displayed distinct labrid assemblages, which were consistent over time, likely due to the influence of the East Auckland Current. There was a consistent depth-related trend for most species, regardless of location. Several species also showed a sex related depth difference. There was also a trend for some species to be associated with certain levels of wave exposure. For most species, the relationship between pectoral fin aspect ratio and the above physical variables was not as strongly evident in this temperate assemblage as has been previously found in tropical reef fish systems. Although some species did follow the predicted shifts in fin aspect ratio with depth and/or exposure, the observed trends were unrelated to fin aspect ratio for many other species. These findings suggest that wave exposure may not be as important for labrids on northeastern New Zealand reefs as it may be in tropical coral reefs systems. The lower fin aspect ratios for New Zealand labrids, compared to tropical labrids, suggest that New Zealand labrids represent a subset of the total pectoral fin diversity in the Labridae. Consequently, the potential for distinct trends in fin aspect ratio and physical variables to be evident may be reduced.
We studied territorial behaviour of the acanthurid surgeonfish Acanthurus sohal and pomacentrid damselfish Plectroglyphidodon leucozona on fringing reefs in Ras Mohammed National Park, Red Sea, ...Egypt. We investigated trespass times, the number of agonistic acts, their intensity and the agonism elicited (number agonistic acts/total trespass time) for all intruders. Five families (Pomacentridae, Chaetodontidae, Acanthuridae, Labridae and Scaridae) were dominant among the 14 we recorded in our study sites. Seven species belonging to four families were resident inside A. sohal territories. Of the other 66 species we observed, 45 are intruders. The territory-holder did not react equally agonistically toward all these intruders. A. sohal showed a high number of agonistic acts against conspecifics and the parrotfish Cetoscarus bicolor. The intensity of the agonistic encounters, however, showed a different picture, with a low level for conspecifics and C. bicolor, respectively. A. sohal showed a high degree of agonistic intensity toward only one parrotfish, Chlorurus sordidus. The highest values of 'Agonism elicited' were recorded against Scarus ghobban, followed by Siganus rivulatus and Zebrasoma desjardinii . Despite these high values, the intensity was relatively weak. The territories of A. sohal were large (average 12.5m^sup 2^); those of P.leucozona were ca. 20 times smaller (average 0.6m^sup 2^). A. sohal spent most of their time swimming (patrolling) along the territory border, stopping briefly to feed on algae. On the other hand, P. leucozona spent most of their time swimming and sheltering.PUBLICATION ABSTRACT
Seagrasses are marine angiosperms widely distributed in both tropical and temperate coastal waters creating one of the most productive aquatic ecosystems on earth. In the Western Indian Ocean (WIO) ...region, with its 13 reported seagrass species, these ecosystems cover wide areas of near-shore soft bottoms through the 12 000 km coastline. Seagrass beds are found intertidally as well as subtidally, sometimes down to about 40 m, and do often occur in close connection to coral reefs and mangroves. Due to the high primary production and a complex habitat structure, seagrass beds support a variety of benthic, demersal and pelagic organisms. Many fish and shellfish species, including those of commercial interest, are attracted to seagrass habitats for foraging and shelter, especially during their juvenile life stages. Examples of abundant and widespread fish species associated to seagrass beds in the WIO belong to the families Apogonidae, Blenniidae, Centriscidae, Gerreidae, Gobiidae, Labridae, Lethrinidae Lutjanidae, Monacanthidae, Scaridae, Scorpaenidae, Siganidae, Syngnathidae and Teraponidae. Consequently, seagrass ecosystems in the WIO are valuable resources for fisheries at both local and regional scales. Still, seagrass research in the WIO is scarce compared to other regions and it is mainly focusing on botanic diversity and ecology. This article reviews the research status of seagrass beds in the WIO with particular emphasis on fish and fisheries. Most research on this topic has been conducted along the East African coast, i.e. in Kenya, Tanzania, Mozambique and eastern South Africa, while less research was carried out in Somalia and the Island States of the WIO (Seychelles, Comoro Is., Reunion (France), Mauritius and Madagascar). Published papers on seagrass fish ecology in the region are few and mainly descriptive. Hence, there is a need of more scientific knowledge in the form of describing patterns and processes through both field and experimental work. Quantitative seagrass fish community studies in the WIO such as the case study presented in this paper are negligible, but necessitated for the perspective of fisheries management. It is also highlighted that the pressure on seagrass beds in the region is increasing due to growing coastal populations and human disturbance from e.g. pollution, eutrophication, sedimentation, fishing activities and collection of invertebrates, and its effect are little understood. Thus, there is a demand for more research that will generate information useful for sustainable management of seagrass ecosystems in the WIO.
We designed a new inverse PCR protocol combined with switching mechanism at 5', end of RNA transcript (SMART) technology, and applied it to the cloning of teleost corticotropin-releasing hormone ...precursor cDNA. Due to the advantages of both techniques, this method can efficiently amplify the complete 5'- and 3'ends of cDNA in a single reaction, and might prove to be an alternative to the conventional rapid amplification of cDNA ends (RACE) approaches.
Many fish species are cryptic by nature or show a negative response to divers. This may make traditional censusing techniques difficult to perform and the results obtained using these methods may be ...inaccurate. This problem will be exacerbated in complex habitats, such as those found on coral reefs, because the cryptic species present will be even more difficult to locate and identify. Predation studies on coral reefs have been especially hampered by this problem because many predatory species are cryptic and so it has been difficult to obtain reliable abundance estimates. This study tested a visual census technique that used bait to bring cryptic predatory fish into view. Results from this census were then compared to those from a traditional survey using belt transects, and to a patch reef tagging study where all individuals of 3 key species were located. The baited technique produced significantly higher density estimates for 3 of the 4 most abundant cryptic species. The patch reef experiment demonstrated that the baited technique accounted for 85 to 96% of fish present. Censuses without bait observed only 40 to 61% of fish present. For mobile species, on the other hand, the baited census appeared to overestimate abundance, due to movement of fish into the census area. We therefore recommend combining baited censuses of sedentary cryptic species with traditional censuses of mobile species to gain an accurate picture of piscivorous reef fish communities. Using this approach at Lizard Island on the Great Barrier Reef, the proportion of cryptic piscivores in the community was found to be almost double that which would have otherwise been observed. We also found considerable spatial variation in the abundance and distribution of piscivorous fish. These patterns would have been quite different had the survey been based on belt transects alone. Previous studies using belt transects may therefore have underestimated the importance of cryptic piscivorous species in communities of coral reef fish.
Many Caribbean coral reefs have experienced an increase in erect brown algae (species ofSargassum,TurbinariaandLobophora) over the past 18 yr. We explored the effects of fleshy algal overgrowth on ...coral reef fishes by reducing erect algae by ~2.5 kg(wet) m–2on 8 patch reefs (average size ~1000 m²) whereby half were in a new no-fishing zone and half in an unrestricted fishing zone. Another 8 reefs were left as unmanipulated controls in the respective zones. Multivariate ordination indicated that the algal removal had marginal effect on whole-fish assemblages but that effect was highly significant on the biomass of common herbivores. The reduction of erect algae resulted in a rapid increase in the abundance of the blue-headed wrasseThalassoma bifasciatum(Labridae), in the biomass of the blue tangAcanthurus coeruleus(Acanthuridae), and in both the abundance and biomass of the spotlight parrotfishSparisoma viride(Scaridae). Bite rates and intra- and inter-specific aggressive encounters were used as measures of resource quality, and we found that these measures increased for surgeonfishes and damselfishes after the algal reduction, particularly in the center of the patch reefs, where most erect algae was originally located. Increased accessibility, net production and palatability of the early successional turf algae on the manipulated reefs are likely to account for the increased numbers, biomass and feeding rates of the dominant herbivorous fishes.
The fish community associated with a fringing reef was studied at Cautaro, Mochima National Park, Venezuela. A systematic sampling based on visual censuses was carried out from December 2000 to May ...2002. A total of 86 species belonging to 31 families were identified, dominated by Scaridae, Haemulidae and Labridae, Pomacentridae and Serranidae, which accumulated, together with the sole species of Sparidae, 77.52% of the total abundance. Diplodus argenteus, Microspathodon chrysurus and Thalassoma bifasciatum were the most abundant and frequent (>50%) species, and considered typical and characteristic of the study area. The total diversity was 4.54 bits ind super(-1) and oscillated between 3.33 and 4.25 bits ind super(-1), with an average of 3.86. Equitability varied between 0.74 and 0.89. The relationship between species abundance and rank was significant and the diversity index of the log-series based on the species number was alpha = 14.19. The trophic analysis of the community indicated that the carnivorous species constituted the dominant group, followed by the herbivores and omnivores. The normal distribution fitted the species abundance data, indicating a tendency towards stabilization in relation to the species number.
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