Academic literature on the topic 'Wrasses'

Resource partitioning in polymorphic fish species is expected to be altered by human exploitation, as individual specialization is density dependent in many vertebrates. We tested this hypothesis using the ballan wrasse Labrus bergylta as a model species. We compared the isotope niches of the plain and spotted morphs of the species in a marine protected area (MPA) and in adjoining areas open to fishing, both off Galicia (NW Spain). Underwater visual census confirmed a 3-fold increase in the biomass of ballan wrasse off the Cíes Islands compared to areas open to recreational fishing, thus demonstrating that populations outside MPAs are well below carrying capacity. The stable isotope ratio of C revealed differences in the resource use patterns of plain and spotted ballan wrasses both in areas open and closed to fishing, as plain wrasses were always depleted in 13C compared to sympatric spotted ones. The stable isotope ratio of N showed that plain ballan wrasses foraged consistently at a higher trophic level than spotted ones in areas of high population density closed to recreational fishing, whereas differences did not exist or were reversed in areas open to fishing. These results demonstrate that the pattern of trophic resource partitioning between 2 morphs of the ballan wrasse is density dependent and that plain and spotted ballan wrasses likely had different ecological niches in pristine ecosystems.

Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae)—a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse (Thalassoma bifasciatum) and the temperate spotty (Notolabrus celidotus) and kyusen (Parajulus poecilepterus) wrasses. In all three species, gonadal sex change was preceded by downregulation of cyp19a1a (encoding gonadal aromatase that converts androgens to oestrogens) and accompanied by upregulation of amh (encoding anti-müllerian hormone that primarily regulates male germ cell development), and these genes may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase (cyp19a1b) in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (it, that regulates teleost socio-sexual behaviours) expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting it upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, it expression was not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.

Abstract Piscivorous wildlife is often perceived as competitors by humans. Great cormorants of the continental subspecies (Phalacrocorax carbo sinensis) in the Baltic and North Sea increase, while local cod (Gadus morhua) stocks decline. In contrast, numbers of the Atlantic subspecies (Phalacrocorax carbo carbo), breeding along the Norwegian and Barents Seas, have been relatively stable. We investigated the diet of both great cormorant subspecies in breeding colonies along the Norwegian Coast from Lofoten to the Skagerrak and estimated the biomass of fish consumed annually by great cormorants in Norwegian waters. The birds’ consumption was compared with estimated fish stock sizes and fishery catches. Cod and saithe (Pollachius virens) dominated the diet in the Norwegian Sea and wrasses in the North Sea and Skagerrak. Estimated total fish consumption of cod and saithe by great cormorants was <1.7% of estimated fish stocks and <9% of that of human catches and therefore considered minor. Cormorant consumption of wrasses amounted to 110% of human catches. The practice of using wrasses as cleaner fish in the salmon farming industry leads to a conflict with cormorants, and we urge for a better understanding and management of wrasse populations, taking ecosystem functioning and natural predation into account.

Abstract Coral reefs are complex marine habitats that have been hypothesized to facilitate functional specialization and increased rates of functional and morphological evolution. Wrasses (Labridae: Percomorpha) in particular, have diversified extensively in these coral reef environments and have evolved adaptations to further exploit reef-specific resources. Prior studies have found that reef-dwelling wrasses exhibit higher rates of functional evolution, leading to higher functional variation than in non-reef dwelling wrasses. Here, we examine this hypothesis in the lower pharyngeal tooth plate of 134 species of reef and non-reef-associated labrid fishes using high-resolution morphological data in the form of micro-computed tomography scans and employing three-dimensional geometric morphometrics to quantify shape differences. We find that reef-dwelling wrasses do not differ from non-reef-associated wrasses in morphological disparity or rates of shape evolution. However, we find that some reef-associated species (e.g., parrotfishes and tubelips) exhibit elevated rates of pharyngeal jaw shape evolution and have colonized unique regions of morphospace. These results suggest that while coral reef association may provide the opportunity for specialization and morphological diversification, species must still be able to capitalize on the ecological opportunities to invade novel niche space, and that these novel invasions may prompt rapid rates of morphological evolution in the associated traits that allow them to capitalize on new resources.

A nearly complete lower pharyngeal tooth-plate from a large (over 60 cm long) fossil wrasse (Perciformes: Labridae) was recently recovered from the middle to late Eocene La Meseta Formation on Seymour Island, Antarctic Peninsula. This find increases the number of teleosts from the Eocene of Antarctica to five taxa, and further illustrates the diversity of the ichthyofauna in the Eocene Weddellian Sea prior to wide-scale climatic change in the Southern Ocean. The fossil wrasse represents the first occurrence of this family in Antarctica, and is one of the oldest fossils of this family from the Southern Hemisphere. Wrasses are not found in Antarctic waters today, and probably became extinct during the Oligocene due to a combination of climatic change, loss of shallow-water habitat, and changes in the trophic structure of the Wedell Sea.

Abstract Small-bodied wrasse species are important for structuring coastal marine ecosystems but are also increasingly harvested as parasite cleaners on farmed salmon. Identifying management regulations that will support long-term sustainability of wrasse fisheries is challenging, because there is still limited knowledge about the impacts of fisheries on the demography of these intermediate predators in their natural environments. To this end, we studied individual growth histories of goldsinny wrasse (Ctenolabrus rupestris) at a fine spatial scale across replicated marine protected areas (MPAs) and areas open to commercial harvesting on the Norwegian coast. The MPAs were established 1–7 years prior to our sampling. We detected significant fine-scale spatial variation in wrasse asymptotic body size, but found no consistent difference between MPAs and fished areas. Male wrasses reached larger asymptotic body sizes than females, whereas fyke nets captured individuals with larger asymptotic body sizes compared with baited traps. These are the two commonly used gear types in wrasse fisheries. An extended use of baited traps, along with slot-size limits, could therefore aid in protecting large-growing phenotypes such as nest-guarding males.

The present study analysed two sympatric wrasses, Thalassoma pavo and Coris julis, with similar sizes and morphologies, that are widespread in the reef habitats of the Mediterranean and the eastern Atlantic coast. Ocean warming has induced the northward movement of T. pavo, whereas C. julis has been moving to deeper habitats. In addition, under conditions of high slope of the sea bottom, T. pavo occupies shallow habitats and C. julis is in greater abundance in deeper habitats. By investigating stomach contents and prey availability in the benthos, we assessed whether the two wrasses exploit food resources by choosing different prey within the same habitat both under co-existence and segregation conditions. The results showed that T. pavo mainly feeds on gammarids and sipunculids, whereas C. julis mainly feeds on Alvania spp. and Paguroidea. The two wrasses also showed an intrinsic partitioning of food resources, independently of the condition of co-existence or segregation and benthic prey availability in the environment. The two wrasses fall in the ‘over dispersion of resource use’ model, in which species share numerous niche dimensions in a variable manner. Our findings may contribute to exclude a greater trophic competition between these labrid species in a projected warming scenario.

Changes in fish communities as oceans warm and cool and competition for space between established and novel species can be evaluated in biogeographic transition zones such as the west coast of Australia. At ~30° S in this region, a cool anomaly occurred in the 2000s, between marine heatwaves. Over 2 yr of that anomaly, surveyed reef fishes were 57% temperate, 18% sub-tropical and 25% tropical. The most numerous fishes included a wrasse, herring, bullseye, drummer and damselfish. Based on similarities in the composition of fishes, 7 significant clusters of reefs were identified along a gradation from deep, exposed reefs to shallow, protected lagoonal reefs. Endemic sub-tropical and temperate wrasses and damselfishes typified all reefs. Some of these were ubiquitous over exposed and lagoonal reefs and others prevalent in only one reef type, demonstrating habitat preferences and partitioning among closely related species. This was reflected in the differing order of importance of fishes that typified different reefs. Linear modelling indicated that abiotic (depth, distance from shore) and biotic factors (e.g. algae) explained most of the variation in the fish communities among reefs. Additional variation, particularly within lagoonal reefs, was related to relief, turf and corals, rather than water temperature. Occurrence and reproductive activity of a group of tropical/sub-tropical wrasses and damselfish in some lagoonal reefs with abundant tropical habitats (e.g. corals) suggested that they supported novel communities during cool anomalies. Better predictions of future change and interactions between existing and novel species with environmental cycles requires knowledge of species-specific habitat relationships and biology.

The genetic impact of farmed fish escaping aquaculture is a highly debated issue. However, non-target species, such as cleaner fish used to remove sea lice from farmed fish, are rarely considered. Here, we report that wild corkwing wrasse ( Symphodus melops ), which are transported long distances to be used as cleaner fish in salmon farms, escape and hybridize with local populations. Recently, increasing numbers of corkwing wrasse have been reported in Flatanger in Norway, north of its described distribution range, an area heavily relying on the import of cleaner fish from Skagerrak. Using genetic markers identified with 2bRAD sequencing, we show that, although the Flatanger population largely is a result of a northward range expansion, there is also evidence of considerable gene flow from southern populations in Skagerrak and Kattegat. Of the 40 corkwing wrasses sampled in Flatanger, we discovered two individuals with clear southern genotypes, one first-generation hybrid, and 12 potential second-generation hybrids. In summary, we provide evidence that corkwing wrasse escape from fish farms and hybridize with local populations at the leading edge of an ongoing range expansion. Although the magnitude and significance of escapees warrant further investigation, these results should be taken into consideration in the use of translocated cleaner fish.

Abstract As different macrophyte habitats house different distributions of invertebrates, we questioned if differences in the composition of fish in these habitats also could be identified. Additionally, we addressed the question if the fish communities could be affected a few years after sugar kelp beds had shifted to degraded turf habitats. Gill-nets of different mesh sizes were used to catch fish in the then four dominating subtidal macrophyte habitats; the kelp species Laminaria hyperborea and Saccharina latissima, the turf algae, and the seagrass Zostera marina. Each habitat was sampled in South Norway, day and night, and at two following months. Altogether, 31 species of fish and five species of larger crustaceans were caught. Both individuals and species numbers were dominated by wrasses and codfish. The wrasses were most active at daytime, while most codfish entered the habitats at night. Wrasses were mainly occurring in the seaweed habitats, while codfish dominated the seagrass samples. The kelps had highest numbers of individuals, while seagrasses showed highest species diversity. The turf habitats did not result in dramatic negative effects on the fish fauna. Fish can take advantage of other adjacent habitats, a benefit that could be reduced by expanding shifts from kelps to turfs.

The biology of four species of Choerodon (Labridae), the blue tuskfish C. cyanodus, the bluespotted tuskfish C. cauteroma, the baldchin groper C. rubescens and the blackspot tuskfish C. schoenleinii was studied in Shark Bay in Western Australia. These species are fished commercially and/or recreationally in this large subtropical marine embayment, which is a world heritage area. The biology of C. rubescens was also studied in the Abrolhos Islands, which are located ~ 300 km to the south of Shark Bay, where this labrid is an important commercial and recreational fish species. The broad aims of this project were to determine the following for the above four Choerodon species in Shark Bay. (1) Whether they are protogynous hermaphrodites, as is the case with many labrids. (2) The biological variables required for developing management plans for these species, such as the timing of spawning, the lengths and ages at both maturity and sex change, size and age compositions and growth parameters, and (3) the habitat types occupied during their life cycles and also of the purple tuskfish Choerodon cephalotes. Finally, comparisons are made between the age and size compositions, growth and reproductive biology of C. rubescens in Shark Bay and the Abrolhos Islands. Where relevant, the underlying hypotheses for the individual studies conducted during this PhD are included in the following chapters. A macroscopic and histological examination of the gonads of the full size range of C. cyanodus, C. cauteroma, C. rubescens and C. schoenleinii, together with an analysis of the length and age compositions of female, transitional (individuals changing sex) and male individuals, demonstrated that each of these species is a protogynous hermaphrodite, i.e. individuals change sex from female to male during their life cycle. The gonads of all small (> < ca 100 mm) and young (> < ca 1 year old) individuals of each species comprised solely ovarian tissue and thus the individuals of each species began life as a female. All individuals subsequently become sexually mature as females and then later in life some will change to males. Since this was found to be the only method of sex change in these species, they are termed monandric. Individuals that were changing sex contained 'undelimited type 2' gonads sensu Sadovy and Shapiro (1987). These gonads contained both ovarian and testicular tissue that was intermixed and not separated by connective tissue. The males of each species possessed secondary testes, which retained structures of the ovary they had replaced, such as a membrane-lined ovarian lumen, lamellae and ovary wall. Furthermore, histological sections indicated that sperm were transported towards the outer walls of the testes, where the multiple sperm sinuses present in that region were presumably responsible for transporting sperm to the cloaca, rather than to a singular sperm duct as is the case with gonochoristic species. The typically large size and different colour of the males of C. rubescens, C. schoenleinii and C. cauteroma and the bias in the sex ratios of their adults towards females suggests that the males of each of these species are either haremic, i.e. permanently territorial, or form leks, i.e. are temporarily territorial during their spawning seasons. In these three species, the presence of ripe testes that are far smaller than ripe ovaries and the release by females of eggs in batches are consistent with a single male spawning with an individual female, as commonly occurs in haremic/lekking species. In contrast to the above species, C. cyanodus was not sexually dichromatic, the sex ratio was not biased towards either sex and the weight of ripe testes remained relatively constant as body weight increased. The latter implies that the relative investment of energy by males into testicular development during the spawning season declines with increasing fish size. Thus, the males of C. cyanodus may be opportunistic spawners when small, possibly spawning in groups, and may tend towards a haremic or lek mode of life when larger. The respective lengths and ages at which 50% of the females of C. cyanodus C. cauteroma and C. schoenleinii attained sexual maturity (L50m, A50m) in Shark Bay were ca 129, 196 and 253 mm and 2.3, 2.0 and 3.5 years of age. The corresponding L50m and A50m for C. rubescens in Shark Bay and the Abrolhos Islands were ca 274 and 279 mm, respectively, and 2.7 and 4.1 years of age, respectively. The respective lengths and ages at which 50% of the females of C. cyanodus, C. cauteroma and C. schoenleinii changed to males (L50c, A50c) in Shark Bay were 221, 310 and 556 mm and 4.1, 6.4 and 10.4 years of age. The length at which C. rubescens changed sex (L50c) was significantly greater in Shark Bay (545 mm) than in the Abrolhos Islands (479 mm), whereas the reverse pertained with respect to the age at sex change (A50c), i.e. 10.5 vs 11.9 years of age. Since some females were found in the oldest age classes of each species in Shark Bay and in the population of C. rubescens in the Abrolhos Islands, some of the females of each species do not apparently change sex. The trends exhibited by the gonadosomatic indices of females and males and the stages of ovarian development in sequential months demonstrated that the spawning periods of each species varied. Thus, C. rubescens (in both Shark Bay and the Abrolhos Islands) and C. cauteroma spawn predominantly in spring, whereas spawning occurs in late spring/early summer in C. schoenleinii and in summer in C. cyanodus. As C. schoenleinii, C. cyanodus and C. cauteroma occur predominantly within the inner gulfs of Shark Bay, the offset in the timing of their spawning periods would be likely to reduce any potential for competition between the larvae of those three species for resources. The trends exhibited by the mean monthly marginal increments in sectioned otoliths with differing numbers of opaque zones demonstrated that, in each species, those opaque zones were laid down annually. Thus, the numbers of opaque zones in the sectioned otoliths of individuals of each species could be used, in conjunction with the birth date and time of year when those zones are delineated, to determine their approximate ages at capture. The maximum ages recorded for the four Choerodon species in Shark Bay ranged only from 12 to 16 years. However, in that environment, the maximum lengths of C. rubescens (649 mm) and C. schoenleinii (805 mm) were far greater than those of C. cauteroma (424 mm) and C. cyanodus (382 mm). In contrast to the situation with C. rubescens in Shark Bay, this species reached a substantially older maximum age (22 years), but slightly shorter length (629 mm), and grew at a slower rate in the Abrolhos Islands, possibly reflecting the influence of greater productivity in Shark Bay and/or greater densities of this species in the Abrolhos Islands. Although a few C. rubescens and C. schoenleinii reach large sizes in Shark Bay, most of the individuals of these species were less than 400 mm, their minimum legal length (MLL) for capture. This raises the possibility that these two sought after species, i.e. the seventh and ninth most abundant species in the recreational fishery in Shark Bay, are subjected to substantial fishing pressure. Sampling for C. cyanodus was considered representative of the sites that this species occupies in Shark Bay and the sampling methods would have been likely to have captured the full size range of this tuskfish. Thus, the failure to catch any C. cyanodus greater than 400 mm indicates that, in Shark Bay, this species does not grow to the far greater lengths of about 600 mm reported for this species as a maximum by Allen (1999). Furthermore, the 400 mm MLL for this species in Western Australia precludes the retention by fishers of this species in this environment. Choerodon cauteroma was caught at lengths up to 424 mm, which is greater than the maximum of 360 mm reported for this species (Allen, 1999). Although there is no MLL for C. cauteroma, recreational fishers are restricted to a bag limit of four fish per person per day, as is the case with all other tuskfish species. Since fishers target large fish preferentially and the largest size classes of each of the species of tuskfish are dominated by males, heavy fishing pressure has the potential to remove a large proportion of the males of the Choerodon species that are fished in Shark Bay, i.e. C. rubescens, C. schoenleinii and C. cauteroma, and also of C. rubescens in the Abrolhos Islands. Since the ratio of females to males in catches of C. rubescens taken by the commercial fishery in the Abrolhos Islands are ca 1:1 and yet the typical adult sex ratio is heavily biased towards females (ca 14:1), that fishery is removing a substantial proportion of the males from the population. Protogynous hermaphroditic species are apparently able to respond to such pressure on the males by initiating a change in sex by the larger females. However, there is evidence from studies of other protogynous species that heavy size-selective fishing can lead to a reduction in the size and age at which a species changes sex and ultimately to a collapse in the stock. The results of visual surveys, when taken in conjunction with the locations of the catches of each of the five Choerodon species, demonstrated that C. rubescens lives on reefs in 'oceanic' waters along the western boundary of Shark Bay, whereas C. schoenleinii, C. cyanodus, C. cauteroma and C. cephalotes are found predominantly in the two inner gulfs of this large embayment. Choerodon cephalotes lives almost exclusively in seagrass beds, while C. schoenleinii and C. cyanodus occupy predominantly inner gulf reefs and rocky shorelines and C. cauteroma occurs in all of those three habitats. Choerodon cauteroma was the only species that underwent an obvious size-related shift during its life cycle, moving from seagrass to hard substrates, such as inner gulf reefs and rocky shorelines, as it reached adulthood. The biological and habitat data produced during this thesis will provide fisheries and environmental managers with the types of information that will enable them to develop management plans for conserving tuskfish species and their habitats in Shark Bay. The biological data for C. rubescens in the Abrolhos Islands will be able likewise to be used to develop plans for conserving the stock of this species in waters in which it is heavily fished.

The biology of four species of Choerodon (Labridae), the blue tuskfish C. cyanodus, the bluespotted tuskfish C. cauteroma, the baldchin groper C. rubescens and the blackspot tuskfish C. schoenleinii was studied in Shark Bay in Western Australia. These species are fished commercially and/or recreationally in this large subtropical marine embayment, which is a world heritage area. The biology of C. rubescens was also studied in the Abrolhos Islands, which are located ~ 300 km to the south of Shark Bay, where this labrid is an important commercial and recreational fish species. The broad aims of this project were to determine the following for the above four Choerodon species in Shark Bay. (1) Whether they are protogynous hermaphrodites, as is the case with many labrids. (2) The biological variables required for developing management plans for these species, such as the timing of spawning, the lengths and ages at both maturity and sex change, size and age compositions and growth parameters, and (3) the habitat types occupied during their life cycles and also of the purple tuskfish Choerodon cephalotes. Finally, comparisons are made between the age and size compositions, growth and reproductive biology of C. rubescens in Shark Bay and the Abrolhos Islands. Where relevant, the underlying hypotheses for the individual studies conducted during this PhD are included in the following chapters. A macroscopic and histological examination of the gonads of the full size range of C. cyanodus, C. cauteroma, C. rubescens and C. schoenleinii, together with an analysis of the length and age compositions of female, transitional (individuals changing sex) and male individuals, demonstrated that each of these species is a protogynous hermaphrodite, i.e. individuals change sex from female to male during their life cycle. The gonads of all small (> < ca 100 mm) and young (> < ca 1 year old) individuals of each species comprised solely ovarian tissue and thus the individuals of each species began life as a female. All individuals subsequently become sexually mature as females and then later in life some will change to males. Since this was found to be the only method of sex change in these species, they are termed monandric. Individuals that were changing sex contained 'undelimited type 2' gonads sensu Sadovy and Shapiro (1987). These gonads contained both ovarian and testicular tissue that was intermixed and not separated by connective tissue. The males of each species possessed secondary testes, which retained structures of the ovary they had replaced, such as a membrane-lined ovarian lumen, lamellae and ovary wall. Furthermore, histological sections indicated that sperm were transported towards the outer walls of the testes, where the multiple sperm sinuses present in that region were presumably responsible for transporting sperm to the cloaca, rather than to a singular sperm duct as is the case with gonochoristic species. The typically large size and different colour of the males of C. rubescens, C. schoenleinii and C. cauteroma and the bias in the sex ratios of their adults towards females suggests that the males of each of these species are either haremic, i.e. permanently territorial, or form leks, i.e. are temporarily territorial during their spawning seasons. In these three species, the presence of ripe testes that are far smaller than ripe ovaries and the release by females of eggs in batches are consistent with a single male spawning with an individual female, as commonly occurs in haremic/lekking species. In contrast to the above species, C. cyanodus was not sexually dichromatic, the sex ratio was not biased towards either sex and the weight of ripe testes remained relatively constant as body weight increased. The latter implies that the relative investment of energy by males into testicular development during the spawning season declines with increasing fish size. Thus, the males of C. cyanodus may be opportunistic spawners when small, possibly spawning in groups, and may tend towards a haremic or lek mode of life when larger. The respective lengths and ages at which 50% of the females of C. cyanodus C. cauteroma and C. schoenleinii attained sexual maturity (L50m, A50m) in Shark Bay were ca 129, 196 and 253 mm and 2.3, 2.0 and 3.5 years of age. The corresponding L50m and A50m for C. rubescens in Shark Bay and the Abrolhos Islands were ca 274 and 279 mm, respectively, and 2.7 and 4.1 years of age, respectively. The respective lengths and ages at which 50% of the females of C. cyanodus, C. cauteroma and C. schoenleinii changed to males (L50c, A50c) in Shark Bay were 221, 310 and 556 mm and 4.1, 6.4 and 10.4 years of age. The length at which C. rubescens changed sex (L50c) was significantly greater in Shark Bay (545 mm) than in the Abrolhos Islands (479 mm), whereas the reverse pertained with respect to the age at sex change (A50c), i.e. 10.5 vs 11.9 years of age. Since some females were found in the oldest age classes of each species in Shark Bay and in the population of C. rubescens in the Abrolhos Islands, some of the females of each species do not apparently change sex. The trends exhibited by the gonadosomatic indices of females and males and the stages of ovarian development in sequential months demonstrated that the spawning periods of each species varied. Thus, C. rubescens (in both Shark Bay and the Abrolhos Islands) and C. cauteroma spawn predominantly in spring, whereas spawning occurs in late spring/early summer in C. schoenleinii and in summer in C. cyanodus. As C. schoenleinii, C. cyanodus and C. cauteroma occur predominantly within the inner gulfs of Shark Bay, the offset in the timing of their spawning periods would be likely to reduce any potential for competition between the larvae of those three species for resources. The trends exhibited by the mean monthly marginal increments in sectioned otoliths with differing numbers of opaque zones demonstrated that, in each species, those opaque zones were laid down annually. Thus, the numbers of opaque zones in the sectioned otoliths of individuals of each species could be used, in conjunction with the birth date and time of year when those zones are delineated, to determine their approximate ages at capture. The maximum ages recorded for the four Choerodon species in Shark Bay ranged only from 12 to 16 years. However, in that environment, the maximum lengths of C. rubescens (649 mm) and C. schoenleinii (805 mm) were far greater than those of C. cauteroma (424 mm) and C. cyanodus (382 mm). In contrast to the situation with C. rubescens in Shark Bay, this species reached a substantially older maximum age (22 years), but slightly shorter length (629 mm), and grew at a slower rate in the Abrolhos Islands, possibly reflecting the influence of greater productivity in Shark Bay and/or greater densities of this species in the Abrolhos Islands. Although a few C. rubescens and C. schoenleinii reach large sizes in Shark Bay, most of the individuals of these species were less than 400 mm, their minimum legal length (MLL) for capture. This raises the possibility that these two sought after species, i.e. the seventh and ninth most abundant species in the recreational fishery in Shark Bay, are subjected to substantial fishing pressure. Sampling for C. cyanodus was considered representative of the sites that this species occupies in Shark Bay and the sampling methods would have been likely to have captured the full size range of this tuskfish. Thus, the failure to catch any C. cyanodus greater than 400 mm indicates that, in Shark Bay, this species does not grow to the far greater lengths of about 600 mm reported for this species as a maximum by Allen (1999). Furthermore, the 400 mm MLL for this species in Western Australia precludes the retention by fishers of this species in this environment. Choerodon cauteroma was caught at lengths up to 424 mm, which is greater than the maximum of 360 mm reported for this species (Allen, 1999). Although there is no MLL for C. cauteroma, recreational fishers are restricted to a bag limit of four fish per person per day, as is the case with all other tuskfish species. Since fishers target large fish preferentially and the largest size classes of each of the species of tuskfish are dominated by males, heavy fishing pressure has the potential to remove a large proportion of the males of the Choerodon species that are fished in Shark Bay, i.e. C. rubescens, C. schoenleinii and C. cauteroma, and also of C. rubescens in the Abrolhos Islands. Since the ratio of females to males in catches of C. rubescens taken by the commercial fishery in the Abrolhos Islands are ca 1:1 and yet the typical adult sex ratio is heavily biased towards females (ca 14:1), that fishery is removing a substantial proportion of the males from the population. Protogynous hermaphroditic species are apparently able to respond to such pressure on the males by initiating a change in sex by the larger females. However, there is evidence from studies of other protogynous species that heavy size-selective fishing can lead to a reduction in the size and age at which a species changes sex and ultimately to a collapse in the stock. The results of visual surveys, when taken in conjunction with the locations of the catches of each of the five Choerodon species, demonstrated that C. rubescens lives on reefs in 'oceanic' waters along the western boundary of Shark Bay, whereas C. schoenleinii, C. cyanodus, C. cauteroma and C. cephalotes are found predominantly in the two inner gulfs of this large embayment. Choerodon cephalotes lives almost exclusively in seagrass beds, while C. schoenleinii and C. cyanodus occupy predominantly inner gulf reefs and rocky shorelines and C. cauteroma occurs in all of those three habitats. Choerodon cauteroma was the only species that underwent an obvious size-related shift during its life cycle, moving from seagrass to hard substrates, such as inner gulf reefs and rocky shorelines, as it reached adulthood. The biological and habitat data produced during this thesis will provide fisheries and environmental managers with the types of information that will enable them to develop management plans for conserving tuskfish species and their habitats in Shark Bay. The biological data for C. rubescens in the Abrolhos Islands will be able likewise to be used to develop plans for conserving the stock of this species in waters in which it is heavily fished.

Genetic variation was examined in bluehead wrasse, Thalassoma bifasciatum, populations along the Florida Keys. Interpretion of mean heterozygosity (H), percent polymorphic loci per population (P), genetic similarity, and F and G statistics demonstrated a clear division of wrasse populations into "northern" and "southern" groups. Correlation and cluster analyses indicated the six reefs can be grouped in a similar fashion based on genetic and environmental data. The conclusion from this analysis of wrasse populations in the Florida Keys is that substantial population subdivision occurs in response to differing selective pressures created by heterogeneous environments.

The use of wrasse (Pisces: Labridae) as cleaner fish to combat infections with the parasitic copepods Lepeophtheirus salmonis (Kroyer) and Caligus elongatus (Nordmann) (sea-lice) in the culture of Salmo salar L. (Atlantic salmon) is now common. Infections with these parasites has caused considerable losses in the industry since its formative years. The use of the wrasse species Ctenolabrus rupestris (L. ) (goldsinny), Centrolabrus exoletus (L. ) (rockcook), Symphodus melops (= Crenilabrus melops) (L. ) (corkwing) and Labrus mixtus L. (cuckoo) as cleaner fish was first suggested in 1988. The use of these species in the industry is now widespread in Scotland, Ireland and Norway. The fish used are normally caught from the wild before being stocked with S. salar smolts during their first year at sea. The fish are routinely collected from waters close to the farm sites to be stocked. As most of the S. salar sea production sites in Scotland are located on the west coast of the country, the wrasse to be used in these sites are normally collected from these waters. The movement of wild fish into farm pens presents a risk of disease transfer from wrasse to S. salar and vice versa. Prior to their use as cleaner fish, these four species of wrasse had received little attention as subjects of scientific study. As a result, there was very little information available in the literature regarding their diseases. The present study was undertaken to investigate the potential pathogens present in wild populations in Scottish coastal waters, and, in particular, which of these pathogens, if any, could be transmitted to the S. salar. The study also investigated the susceptibility of wrasse to the two major viral diseases of S. salar to which they would be exposed in pens. In order to fully assess the pathogenicity of the potential disease agents under farm conditions, it was first necessary to establish the normal morphology of the wrasse species. Hence, a study of the morphological features of wrasse, with particular emphasis on those features important in the health of the fish was undertaken. Wrasse were shown to differ in many aspects from salmonids but shared many morphological features with other perciforme fish. Major differences from salmonids were evident in the skin, fins, pancreas, intestine, gonads and heart. There were also aspects of their morphology which differed from other perciforme fish, notably the structure of the heart. These features were regarded to be adaptations to the specific demands of their feeding strategies and habitats. This study was the first of its kind undertaken for wrasse and showed some early contraindications for the use of wrasse in culture; most notable was the marked lipid accumulation in, and resultant degeneration of, the liver resulting from the consumption of high energy S. salar feeds. Once the normal morphological features were established, it was possible to examine the disease status of wrasse. Wild fish were sampled from three different locations on the west coast of Scotland. These sites were all geographically distinct and were all used as sources of wrasse for the S. salar farming industry. Samples of wrasse were also obtained from farm sites supplied with wrasse from these wild sites, and an additional number of other geographically distinct farm locations. As a comparison wrasse were also obtained from a wrasse captive breeding facility and another captive location unrelated to the S. salar industry, a public aquarium. The fish from all of these sampling sites were examined fully for the presence of parasites, bacteria and, in some cases, viruses. Histological examination was also carried out on all of the fish studied. A total of 24 new parasite host records, and two tentative ones, were recorded from the four wrasse species studied. These new parasite records included protozoa, digeneans, nematodes and crustacea. Parasite infections were found to vary in prevalence, abundance and intensity in respect to the geographical characteristics of sampling sites and also the length of time spent in S. salar pens. It was concluded that the separation of wrasse from their natural diet and habitat influenced the degree of parasitism. None of the parasites found to infect wrasse were observed to cause any significant pathology in their hosts other than localised tissue responses. The possibility of transfer of wrasse parasites to S. salar was also investigated experimentally in a series of infections in which parasites dissected from wrasse were introduced to S. salar smolts by means of a novel gavage method. None of the parasites used established in the S. salar, indicating that there is little risk of transfaunation of parasites between wrasse and S. salar. However, this aspect requires further work due to the low number of parasites available and the subsequent low numbers of S. salar infected. Bacterial isolates were obtained from wrasse held in S. salar pens but were not found in any of the fish collected from the wild. Most of the bacterial strains isolated would normally be considered as opportunistic pathogens of fish. It was concluded that the relatively high levels of stress, both environmental and physical, that wrasse are subjected to under farm conditions were instrumental in the number of bacterial infections seen in wrasse. Only one pathogenic bacterial infection was seen in any of the fish sampled. This was an isolate of Aeromonas salmonicida, the agent known to cause the disease furunculosis, isolated from a wrasse obtained from one of the farm samples. Other authors have reported that this bacterium has already caused substantial losses of wrasse under farm conditions. It was concluded that Aeromonas salmonicida will prove to be a major pathogen of wrasse held in S. salar pens. No viruses wereI isolated from any of the wrasse studied. The susceptibility of wrasse to the most significant pathogens of S. salar under farm conditions was also subjected to investigation. In addition to sea-lice infection, the industry lists Infectious Pancreatic Necrosis (IPN) and Pancreas Disease (PD) as of primary importance for further research. Both of these diseases cause substantial losses in the industry. The susceptibility of wrasse to both of these disease conditions was investigated by means of experimental infections. In the case of IPN wrasse were infected by bathing with two different infective doses, a low dose which would be expected to induce the disease in S. salar parr and a second dose substantially higher than the first. The C. rupestris used were found to be susceptible to IPN. The wrasse developed some of the pathological characteristics typical of the disease in S. salar, however, other pathological signs were peculiar to wrasse. The recovery rate from the disease seen in wrasse was far more rapid than that recorded from S. salar. Shedding of the virus in the faeces of infected C. rupestris was also demonstrated. This study has illustrated for the first time the susceptibility of wrasse to IPN and that they can shed the virus in their faeces. This suggests that infected wrasse could be a source of continual reinfection in an affected sea site. Experimental infections of C. rupestris with PD followed a standard protocol for the reproduction of the disease in S. salar. Infection was by means of intraperitoneal injection with putatively infective material obtained from S. salar affected with PD. Two infection doses were used, the lowest dose used had been proven to be effective in inducing the disease in S. salar parr while the second dose, ten times higher than the first, had been shown to be effective in reproducing PD in S. salar smolts. The C. rupestris infected did not develop any of the typical signs of the disease seen in S. salar. It was, therefore, concluded that wrasse were not susceptible to PD.

Fishes represent half of all of the living species of vertebrates that have been described to date. Most species of fish are marine, with at least a third found exclusively in coral reefs. Yet the phylogenetic relationships of coral reef fishes and the drivers of their diversification remain poorly understood, particularly for taxonomic groups at the incipient stages of speciation. Despite the increasing application of high-throughput sequencing techniques to other taxonomic groups, much of the research conducted on coral reef fishes still relies on more traditional sources of information, such as morphology and mitochondrial sequence data. These methods are unreliable in resolving taxonomically problematic groups such as the Labridae, where many groups are still rapidly radiating, and the processes driving this are not well understood. It is therefore prudent to use a combined, integrative approach using both morphological and high-throughput sequencing techniques. This thesis uses the aforementioned techniques, integrated with morphological studies, to tease apart the relationships for members of the Labridae, in particular the fairy and pencil wrasses (Cirrhilabrus and Pseudojuloides respectively). Additionally, it includes taxonomic descriptions of eight new species, as well as investigations into general themes on coral reefs, including, but not limited to hybridisation, deep reef communities, and historical biogeography.

This study investigates the characteristics and use of spawning sites by the bluehead wrasse Thalassoma bifasciatum in Barbados, and movements of wrasses from source reefs to proximate and isolate recipient reefs. Pair spawning rate increased with increasing projection height; group spawning rate increased with increasing proximity to the downcurrent reef edge. Daily group spawning rates, but not pair-spawning rates, were higher when daily current speeds were lower, suggesting that fertilisation rates in group spawns may be more sensitive to current speed than fertilisation rates in pair spawns. Migration rate to isolated reefs was 16% that to proximate reefs. Immigration rate to recipient reefs decreased with increasing distance from the source reef and increased with increasing population density on the source reef. Immigration rates to proximate reefs were phase, sex, and size-specific, and were strongly influenced by phase, sex, and size-specific differences in home range size of wrasses. Immigration to isolated reefs was also phase and sex-specific. (Abstract shortened by UMI.)

The biogeography of wrasses within the Western Indian Ocean (WIO) is poorly understood, with regard to origins and genetic differentiation or connectivity among the regions of the WIO. This region is a good model for studying the influence of physical complexities and biogeographic breaks in shaping patterns of differentiation in wrasses. Three reef-associated fish species, Cheilio inermis, Thalassoma hebraicum and T. lunare, were selected to examine the factors that have influenced patterns of differentiation across the WIO. Each species was sampled from various localities of the WIO, the Red Sea and Indo-West Pacific Islands. Sequence data were generated from two mitochondrial gene fragments (cytochrome b and ATPase 6) and one nuclear locus (the first intron of the ribosomal protein S7 gene). Genetic analyses were used to calculate genetic diversity indices within species, which were then compared among species. The relationships among haplotypes and alleles were constructed using median-joining networks. Where necessary, neighbour-joining trees (NJ) were constructed to examine relationships among haplotypes and alleles for the Thalassoma species. Population structure was analysed using AMOVA and pairwise ФST to compare and calculate differentiation between the WIO localities. Mismatch distributions were used to examine population growth and decline or stability, and demographic parameters were used to calculate time of population expansion. There was high haplotype (h = 0.88 to 0.98) and low nucleotide diversities (π = 0.003 to 0.008) among all species for mitochondrial markers. For S7 intron I, high allelic (A = 0.95 to 0.98) and low nucleotide diversities (π = 0.002 to 0.014) were observed for all species. The pairwise ФST values revealed little to great (ФST = -0.02 to 0.67) genetic differentiation between localities, across all species for the three gene regions. The pairwise comparisons indicated the differentiation in C. inermis of Tanzania and Kenya from Mozambique and Nosy Be (Madagascar). The widespread C. inermis also revealed the differentiation of Kenya and Tanzania. For C. inermis, the AMOVAs of ATPase 6 and cytochrome b data indicated high differentiation among defined locality groups. The groups were defined according to geographic proximity. However, the AMOVA of the nuclear gene (S7 intron I) did not find variation among defined locality groups. Cheilio inermis revealed a sequence divergence of 0.4%. The divergence that was found in C. inermis was not enough to suggest a cryptic species within the WIO. Overall, the widespread and monotypic C. inermis revealed genetic differentiation within the WIO. Thalassoma hebraicum generally revealed little genetic differentiation across the WIO. The AMOVAs of the three gene regions showed no variation among specimens of the defined locality groups. However, some differentiation was found between localities. The pairwise comparisons of T. hebraicum revealed the differentiation of Seychelles from the African mainland and Madagascar. Southern Africa was observed to be differentiated from Nosy Be and Zanzibar. The observed differentiation could be caused by oceanic barriers such as the South Equatorial Current (SEQC), East African Coastal Current (EACC), and the Comoros Gyres and eddies in the Mozambique Channel, and Agulhas Current. Thalassoma lunare revealed genetic isolation between the WIO and the Red Sea as well as within the WIO. The genetic isolation between the WIO and the Red Sea is probably due to the historical isolation by the Bab al Mandab and contemporary barriers such as the cold upwelling cells in Somalia. The differentiation of Maldives from the African mainland and Seychelles could be due to distance and the upwelling cells created by monsoon winds. Mismatch distributions suggested that C. inermis and T. hebraicum had undergone demographic expansion during the Pleistocene (92 678 to 40 219 years ago). The results of the current study are similar to those from previous studies of WIO reef fish species, and the results of the present study could have potential implications for conservation and fisheries management. Single genetic markers and single species studies do not detect all barriers to dispersal in the WIO, thus they are insufficient to inform conservation management. Thus, the use of multispecies and genetic markers in the current study can be adopted by other studies of the marine taxa of the WIO.

Cleaner fish, including ballan wrasse (Labrus bergylta) have been proposed as a sustainable solution to sea lice infestations affecting farmed Atlantic salmon (Salmo salar) globally. However, in order to become sustainable, ballan wrasse need to be farmed. This thesis investigated the establishment of captive broodstock and protocols to optimise hatchery performance and productivity of ballan wrasse. High throughput sequencing was used to develop a panel of novel single nucleotide polymorphic markers (SNPs). These SNPs were used to investigate the phylogeographic structuring of ballan wrasse populations within northern geographic ranges including the UK and Norway. Results indicated fine scale population structuring within the UK suggesting that founder broodstock should be sourced locally to minimise the risk of genetic introgression with wild ballan wrasse. Secondly, captive breeding was benchmarked from harems to determine total egg production over the spawning season. Data quantified the spawning periodicity and seasonal changes in egg quality parameters. In addition, microsatellite markers identified the parental contribution to each spawning event of captive broodstock. Results confirmed, for the first time, the repeat-batch spawning behaviour and suggested that spawning events were single-paired matings. Furthermore, bottlenecks in commercial production were investigated including the benthic adhesive eggs and complex spawning behaviours of ballan wrasse within broodstock tanks. Experiments were conducted to optimise the spawning dynamics and egg productivity using fragmented spawning zones and coloured substrates. Finally, an effective bath treatment for removal of the adhesive gum layer of eggs using the proteolytic enzyme alcalase® was found to assist in egg disinfection and incubation. Overall, this research provides important baseline data on the management of broodstock and the optimisation of hatchery protocols to improve the commercial productivity and performance of ballan wrasse for use as a biological control of sea lice of farmed Atlantic salmon.

Stressful situations include abiotic factors such as exposure to hypersaline waters derived from desalination plants and biotic factors such as infection by new parasites introduced by human activities. The aim was to study the effects of an abiotic factor (salinity) and a biotic factor (ectoparasite) on the small coastal wrasse Coris julis (Linnaeus, 1758). Specimens were obtained in three areas of the Island of Ibiza (Balearic Islands): control area, area influenced by the desalination plant and area with high levels of parasite infection. Biomarkers of oxidative stress in the gills, liver and epithelial mucus were analysed, as well as immunological markers in the mucus. The two stress factors induced a differential response, with a greater effect of salinity on the gills and a greater effect of the parasite on the liver and mucus. Innate immunity increased in the mucus of fish under both stressors, and immunoglobulin levels increased only in the presence of parasite. In conclusion, C. julis specimens affected by salinity and an ectoparasite respond with an increase in antioxidant and immunological defence mechanisms.