Since the introduction of the invasive tropical alga Caulerpa taxifolia in the Mediterranean Sea, a new, uniformly green habitat has been available to local fish assemblages. Underwater visual ...censuses of three species, Symphodus ocellatus, Symphodus roissali and Coris julis, revealed a higher proportion of green morphs in the C. taxifolia meadows compared to those inhabiting their usual indigenous habitats. In a fourth species, Symphodus rostratus, the distribution of the different colour morphs did not differ between the two habitats investigated. Experiments in aquaria proved that S. ocellatus and S. roissali were homochromic species able to adapt their colouration to the environment. In contrast, no colour change was observed in S. rostratus during the experiments. Copyright 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.
Shore fish community structure off the Jordanian Red Sea coast was determined on fringing coral reefs and in a seagrass-dominated bay at 6 m and 12 m depths. A total of 198 fish species belonging to ...121 genera and 43 families was recorded. Labridae and Pomacentridae dominated the ichthyofauna in terms of species richness and Pomacentridae were most abundant. Neither diversity nor species richness was correlated to depth. The abundance of fishes was higher at the deep reef slope, due to schooling planktivorous fishes. At 12 m depth abundance of fishes at the seagrass-dominated site was higher than on the coral reefs. Multivariate analysis demonstrated a strong influence on the fish assemblages by depth and benthic habitat. Fish species richness was positively correlated with hard substrate cover and habitat diversity. Abundance of corallivores was positively linked with live hard coral cover. The assemblages of fishes were different on the shallow reef slope, deep reef slope and seagrass meadows. An analysis of the fish fauna showed that the Gulf of Aqaba harbours a higher species richness than previously reported. The comparison with fish communities on other reefs around the Arabian Peninsula and Indian Ocean supported the recognition of an Arabian subprovince within the Indian Ocean. The affinity of the Arabian Gulf ichthyofauna to the Red Sea is not clear.
The genus
Pseudolabrus comprises 11 species of marine nearshore fishes which are antitropically distributed: two species occur in East Asia, the remaining nine species being distributed in the ...Southern Hemisphere, mainly in the temperate Pacific. The distributions of their closely allied genera, collectively called “pseudolabrines” are, however, restricted to the Australia-New Zealand region. The molecular phylogeny of six of the 11
Pseudolabrus species from both Hemispheres and four of the five other pseudolabrine genera was reconstructed from nucleotide sequence data from mitochondrial DNA 12S rRNA, tRNA
Val, and 16S rRNA genes. Both parsimony and Bayesian analyses were performed. Results are not consistent with a previous phylogenetic hypothesis based on osteological data, particularly in the relationship between
Pseudolabrus and
Notolabrus, indicating a probable need for reviewing the status of
Notolabrus (or the delimitations of both
Pseudolabrus and
Notolabrus). The two Northern Hemisphere species of
Pseudolabrus were monophyletic and nested deep into the clade of the Southern Hemisphere pseudolabrines, which indicates that both pseudolabrines and
Pseudolabrus originated in the Southern Hemisphere. A dispersal rather than vicariance explanation for the antitropical distribution of
Pseudolabrus is more parsimonious given the number of dispersal events, extinctions, and evolutionary adaptations required under the phylogeny. Based on molecular clock calibrations, the transequatorial divergence was suggested to be early to mid Pliocene at the earliest.
The age of sex reversal of the venus tusk fish Choerodon venustus, caught by line fishing at various locations on the southern Great Barrier Reef, indicated that C. venustus is capable of modifying ...its life cycle in response to increased mortality. The evidence suggests Masthead Reef fish, which experience the highest mortality, underwent sex reversal at a smaller size and younger age than at the other sites. The largest female fish, sexually transitional fish and males were smaller at Masthead Reef than at the Swains Reefs or One Tree Reef at Masthead Reef. There was also considerable overlap in the size of males and females within the exploited populations indicating that sex reversal is not initiated at a particular length but may have a social cause. The sex ratio of fish was essentially the same for fish fully susceptible to line fishing in the Swains and Masthead samples. Circumstantial evidence suggested that the absence of large males in a population may initiate sex reversal, indicating the maintenance of a constant sex ratio may have a social basis.Copyright 2002 The Fisheries Society of the British Isles
Three new species of Huffmanela, here described from eggs only, are reported from the gills of marine fish caught off Nouméa, New Caledonia. Eggs of Huffmanela branchialis n. sp., from Nemipterus ...furcosus (Nemipteridae), are 45-52 (mean 48) microm in length and 23-30 (mean 25) microm in width, with thin shells. Each egg is enclosed in a thin membrane forming a spindle-shaped envelope 53-85 (mean 63) microm in length. Eggs of H. filamentosa n. sp., from Gymnocranius grandoculis (Lethrinidae), are 48-53 (mean 50) microm in length and 25-30 (mean 27) microm in width, with thin shells. Each egg bears a few long (150 microm), thin filaments. Eggs of these two new species were compared to those of H. paronai Moravec & Garibaldi, 2000, which are redescribed. Eggs of H. ossicola n. sp. were found within the branchial arch bone of Bodianus loxozonus (Labridae) and also filled the spinal chord bone and other bones. This is the first species of Huffmanela reported from bone tissue. Eggs are large, 72-88 (mean 79) microm in length and 32-40 (mean 36) microm in width, with a very thick shell. Each egg is covered with numerous filaments enclosed in a thin envelope. Fresh eggs were unembryonated, but embryos were visible after incubation in seawater. The three new species can be distinguished from other species of Huffmanela by size and the nature of the egg covering. Egg morphology of and their location in the host suggest different life-cycles: those of the first two species (small eggs, thin shells, egg covering possibly favouring flotation) are released from the gill mucosa with the turnover of living tissues and immediately continue their life-cycle, but eggs of H. ossicola (large eggs, thick shell) are only available for the continuation of the life-cycle after the host's death.
Few time series collections have been made of the larval ichthyofauna in waters directly above shallow coral reefs. As a result, relatively little is known regarding the composition and temporal ...dynamics of larval fish assemblages in shallow-reef waters, particularly those near a major western boundary current. We conducted a series of nightly net tows from a small boat over a shallow reef (Pickles Reef) along the upper Florida Keys during four new moon and three third-quarter moon periods in July (two new moons), August, and September 2000. Replicate tows were made after sunset at 0–1 m and at 4–5 m depth to measure the nightly progression in community composition, differences in depth of occurrence, and abundance and diversity with lunar phase. A total of 66 families was collected over the 3-month period, with a mean (±SE) nightly density of 23.7±2.1 larvae per 100 m³ and diversity of 24.2±0.9 taxa per tow. A total of 28.8% of the catch was composed of small, schooling fishes in the families Atherinidae, Clupeidae, and Engraulidae. Of the remaining catch, the top ten most abundant families included reef fishes as well as mangrove and oceanic taxa (in descending order): Scaridae, Blennioidei (suborder), Gobiidae, Paralichthyidae, Lutjanidae, Haemulidae, Labridae, Gerreidae (mangrove), Balistidae, and Scombridae (oceanic). These near-reef larval fish assemblages differed substantially from those collected during previous offshore collections. Taxa such as the Haemulidae were collected at a range of sizes and may remain nearshore throughout their larval period. Overall, the abundance and diversity of taxa did not differ with depth (although within-night vertical migration was evident) or with lunar phase. Temporal patterns of abundance of larval fish families clustered into distinct groups that in several cases paralleled family life-history patterns. In late July, a sharp shift in larval assemblages signaled the replacement of oceanic water with inner shelf/bay water. In general, the suite and relative abundance of taxa collected each night differed from those collected on other nights, and assemblages reflected distinct nightly events as opposed to constant or cyclical patterns. Proximity to the Florida Current likely contributes to the dynamic nature of these near-reef larval assemblages. Our results emphasize the uniqueness of near-reef larval fish assemblages and point to the need for further examination of the biophysical relationships generating event-related temporal patterns in these assemblages.
During the spring and summer of 1999, mortalities occurred in 1-2 year old juvenile tautog being held for nutritional studies at the Milford Laboratory. Internal examination of the dead fish revealed ...that most contained large numbers of white, round nodules. Nodule imprints and histological sections stained with Kinyoun Acid-Fast stain revealed the presence of acid-fast, rod-shaped bacteria. To prevent infection of other tautog at the facility and to determine the extent of infection, the remaining fish were sacrificed and examined for the presence of nodules. Thirty six of the 123 fish examined (29%) had evidence of nodular growth. Multiple organ involvement of nodule growth was found in 71.43% of the infected fish. Nodules were found primarily in kidney tissue (85.71%), liver (57.14%) , and spleen (45.71%). Nodules also were seen to a lesser extent in the heart (20.0%), visceral membrane (11.4%) and one instance each in the intestines and gonads (2.9%). With the exception of a few heavily infected fish which became lethargic and had swollen abdomens, very few signs of external pathology were noted. Slow-growing, acid-fast bacteria were isolated from the nodules using Middlebrook 7H10 Agar media supplemented with ADC enrichment media. After 2-3 weeks, visible growth of raised, roughly textured, off-white colonies was observed. Ongoing and future plans for these isolates call for identification to species level and pathogenicity testing by challenge in healthy tautog. Several species of Mycobacteria have been found to cause diseases in a number of aquatic species including frogs, amphibians, and both freshwater and saltwater fishes. Some of the these same organisms also have been known to infect humans. This is the second known occurrence of mycobacteriosis in the tautog or the wrasse (Labridae) family of fishes. Aquaculturalists should be made aware of the possible infection of their stocks by this pathogen.
It has been suggested that individuals may prevent partners from cheating by building up relationships slowly, giving very little in the beginning and raising the stakes in subsequent moves if ...partners reciprocate. I tested this idea with field experiments on the cleaner-fish Labroides dimidiatus and its "client" reef fish. Clients visit cleaners at their small territories, so-called cleaning stations, to have parasites removed. Cleaners were first observed and then caught and either put back on their original territory or moved to a new site. I noted a variety of cleaner and client behaviour to evaluate how, if at all, relationships are built up. Cleaners and resident clients indeed build up relationships, but with heavy initial investment. There was no evidence that cleaners build up relationships with client species that have access to several cleaners. Finally, it appeared that cleaners constantly invest in relationships with predatory clients, possibly to reduce the risk that predators try to catch them. I propose that asymmetries between partners with respect to either payoff values or strategic options are the major reason why the results do not fit the so-called raising-the-stakes strategy.
Fishes of the Pelican Cays, Belize Smith, C. Lavett; Tyler, James C.; Davis, William P. ...
Atoll research bulletin,
2003, Letnik:
497
Journal Article
The Pelican Cays are a distinctive group of mangrove islands in the south central part of the Belize Barrier Reef Complex. As part of a coordinated investigation of biodiversity in the Pelican Cays, ...we sampled fishes using a combination of small rotenone stations and visual censuses. The Pelican Cays are part of a structurally defined larger group called the Rhomboidal Cays. We have records of 193 species of fishes from the Rhomboidal Cays, 168 from the Core Pelican Cays and 123 from the Peripheral Rhomboidal Cays. By contrast, 293 species are known from the Offshore Banks, 339 from the Barrier Reef, 106 from the Mid-Shelf area exclusive of the Peripheral Rhomboidal Cays, and 150 from the Coastal Marine region, a total of 497 from the entire region. Twelve wide-ranging species recorded from the Pelican Cays have not been found in the other nearby areas. An undescribed species of wrasse, Halichoeres sp., is known only from the Rhomboidal Cays, and an undescribed serranid, Hypoplectrus sp., is abundant in the Pelican Cays, with a single record from Wee-Wee Cay. Other special features of the Pelican Cays are the conspicuous absence of some common species, such as the bluehead wrasse, Thalassoma bifasciatum, and differences in habitat of the blenny Acanthemblemaria aspera.
Trials were conducted in experimental tanks and in commercial scale sea cages to evaluate the ability of wrasse to control sea lice infestations on farmed Atlantic salmon smolts. In a 3 h tank trial ...rockcook wrasse,
Centrolabrus exoletus (L.), removed an average of 19 lice per fish h
−1 from salmon smolts infested mainly by
Caligus elongatus Nordmann (93%) and with lower numbers of
Lepeophtheirus salmonis (Krøyer) (7%). Goldsinny wrasse,
Ctenolabrus rupestris (L.), did not remove lice from salmon over this 3 h period. Chalimus stages I and II were removed at a lower rate than were older and larger life history stages.
Both species of wrasse failed to prevent rapid increases in infestations of
C. elongatus in commercial cages in 1992 and 1993 at initial wrasse to salmon ratios ranging from 1:37 to 1:146. However, SCUBA diving observations confirmed that both wrasse species did remove
C. elongatus from salmon in these cages.
In the 10 m deep cages, wrasse occurred mainly at depths greater than 6 m while salmon occurred primarily between 2 and 5 m. Goldsinny had a significantly shallower distribution than rockcook. Both species associated closely with the cage net and with objects in the cage and interactions with salmon appeared to be relatively uncommon.
Rigorously controlled trials on commercial farms need to be carried out in order to define protocol for the use of wrasse under these conditions.
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