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.
The magnitude and synchrony of spatial and temporal patterns of larval supply to the San Blas Archipelago were measured using three replicate light traps in each of three habitats (exposed, lagoon ...and back-reef) over 18 consecutive lunar months from December 1996 to June 1998.
The continuous reef tract on the semi-exposed side of Lizard Island, northern Great Barrier Reef, can be divided into 6 habitat zones, which are distinctly different in terms of their physical ...(depth, slope and wave exposure) and biological characteristics (percentage of living cover, percentage cover of each substratum type, substratum diversity and complexity). Sixty-four labrid species were found to use these habitat zones in 5 surveys conducted over 3 yr. Thirty-eight species (1804 individuals) were recorded in a single survey (area, 13500 m2), of which 8 were abundant (n > 5% of total number of individuals), 6 were common (1 % < n < 5 % of total) and 24 were rare (n < 1 % of total). Seven of the abundant species showed strong patterns of habitat use, such that the assemblages of these species differed significantly among habitat zones (p < 0.0001). Only 1 abundant species, Labroides dimidiatus, occurred in similar densities in all habitat zones. Depth appeared to be of overriding importance in determining habitat use, with most species occurring either in shallow or deep zones. Within depth ranges, the labrid assemblages differed among habitat zones in terms of the relative abundance of species. In contrast, no clear relationship was detected between labrid density or diversity and other habitat features such as percentage living substratum, substratum diversity or complexity. These patterns were consistent at each of 3 sites separated by >1 km and over 3 yr and 2 seasons (summer and winter). Only 2 of the 8 abundant species showed different patterns of habitat use by adults and recruits, suggesting ontogenetic shifts in habitat use by these species. In contrast, the others showed no evidence of ontogenetic shifts in habitat use, inferring that recruitment patterns may be important in structuring patterns of habitat use by these species. Further studies are now required to test this hypothesis.
. The coastal fish assemblage in three protected sites and one unprotected area in the Slovenian part of the Gulf of Trieste (Northern Adriatic) was studied. Species composition and richness were ...comparable at all studied sites, including the control, unprotected area. Differences in fish density between the protected area of Debeli rtič and the unprotected area of Fiesa‐Pacug were revealed using correspondence analysis. Particularly the densities of certain labrid species (Symphodus cinereus and S. roissali) were higher in the protected area. Those differences are attributable to the extended and densely vegetated infralittoral belt of the Debeli rtič area rather than to its protected status.
Understanding the dynamics of open marine populations is inherently complex, and this complexity has led to decades of debate regarding the relative importance of pre- versus post-settlement ...processes in structuring these populations. Movement between patches may be an important modifier of patterns established at settlement, yet local immigration and emigration have received less attention than other demographic rates. I examined loss rates from tagged populations of juvenile wrasses (yellowhead wrasse Halichoeres garnoti and bluehead wrasse Thalassoma bifasciatum) at two sites in the Bahamas. Assuming that all losses were due solely to mortality would have significantly underestimated survivorship of yellowhead wrasse by 29% and bluehead wrasse by 14%. On average, per capita mortality and emigration rates were higher for yellowhead than bluehead wrasse, but neither demographic rate differed between sites for either species. With respect to within-species density, bluehead wrasse mortality was density-dependent at the patch reef site, but mortality rates of yellowhead wrasse were consistently density-independent. Evaluating the effects of between-species density, yellowhead wrasse mortality increased with a decrease in bluehead wrasse density, but this effect was limited to the patch reef site. Emigration rates were not a function of either within-species or between-species density, but instead varied inversely with isolation distance. Numerous previous studies of coral-reef fish, conducted on patch reefs separated by only a few meters of sand and often using untagged fish, may have confounded losses due to emigration with those due to mortality. A better understanding of the factors affecting emigration in marine fishes is important to their effective management using spatial tools such as marine protected areas.PUBLICATION ABSTRACT
Julis blochii Valenciennes in Cuvier and Valenciennes (1839), allegedly from the East Indies, a new name for Labrus lunare (non Linnaeus) Bloch (1791), was suspected as a senior synonym of Thalassoma ...jansenii (Bleeker, 1856). Instead it is a junior synonym of Thalassoma pavo (Linnaeus), a common and widespread eastern Atlantic species, the result of locality error. Two other Atlantic species, T. sanctaehelenae (Valenciennes, 1839) and T. ascensionis (Quoy & Gaimard, 1834), sometimes considered synonymous, are demonstrably distinct.
The importance of the canopy of small-sized seagrasses (Cymodocea nodosa and Zostera noltii) to fish assemblages was investigated in experimental plots at three shallow sites in NE Sardinia (Italy, ...western Mediterranean). Fish were assessed by underwater visual census in four habitats: (1) seagrass in its natural state, (2) cut seagrass, (3) uncut seagrass (with a simulation in time and effort equivalent to those spent at the treated patches) and (4) unvegetated sand. The disturbance associated with removing seagrass canopies was not found to affect fish. Multivariate analyses showed that fish assemblages from seagrass habitats, with seagrass patches removed and unvegetated sand differed significantly among each other. Univariate analyses revealed that species richness, total fish abundance, and densities of Atherinidae, Diplodus sargus and Sarpa salpa were unaffected by the habitat type. The seagrass leaf canopy was most important for Symphodus ocellatus, Labrus viridis, Diplodus annularis and Sparus aurata, the last three species being chiefly represented by small-sized fishes. Gobiids were most abundant in habitats devoid of seagrass vegetation (i.e. sand and removed patches), while Coris julis and Diplodus vulgaris appeared to prefer unvegetated sand, even compared with the removed patches. Other species, such as Symphodus cinereus, Symphodus tinca and Mullus surmuletus, did not display any distinct distribution patterns attributable to the habitat type. For a number of littoral fish species, including some of commercial importance (e.g. S. aurata), small-sized seagrasses in NE Sardinia were thus demonstrated to exert an ecological role, which involves important implications for the protection and management of these coastal habitats and suggests the need for further research at larger spatial scales.
At least 51 species of fishes are facultative symbionts of sea anemones. Most of the behavioural, ecological and physiological aspects of these associations including their costs and benefits are ...unknown. We recorded the behaviour and the habitat use of eight assemblages (three or ten specimens each) of the juvenile wrasse
Thalassoma amblycephalum dwelling among the tentacles of the two sea anemones
Entacmaea quadricolor (clonal type), and
Heteractis magnifica at a coral reef in southern Japan during 16 months in daylight hours. There are only two past records of this facultative association, one from east Africa and one from Indonesia. The wrasse remained close to and was occasionally in physical contact with the host when foraging amongst the tentacles. When frightened, they took shelter among corals, away from the host anemone. The wrasse co-existed with the anemonefishes
Amphiprion frenatus in
E. quadricolor and
A. ocellaris in
H. magnifica. By using forced host contact tests ex situ and scanning electron microscopy examination of the fish epidermis, we show that juveniles of this wrasse are protected from
E. quadricolor, but possibly not from
H. magnifica. We suggest that juvenile
T. amblycephalum dwelling among the tentacles of sea anemones are cleanerfish with an unusual client, in that they appear to clean mucus and, or, necrotic tissue from the sea anemone host.
Ultrasonic transmitters were surgically implanted into adult tautog (n=27, 400-514 mm TL) to document seasonal occurrence and site utilization at four sites situated within known tautog habitat near ...Cape Charles, Virginia, in lower Chesapeake Bay. Tagged tautog were released at the same sites where originally caught within 2 h of capture. Sites were continuously monitored with automated acoustic receivers between 9 November 1998 and 13 October 1999. Two sites consisted of natural bedform materials and two sites consisted of manmade materials. Ninety-four percent of tautog (n=15) released in fall 1998 remained inshore during winter at sustained water temperatures of 5-8 degree C, rather than moved offshore during winter as documented for tautog off New York, Rhode Island, and Massachusetts. Ninety-one percent (n=10) of tautog released in spring 1999 remained inshore during summer when water temperature was 27 degree C and in the absence of an important food item, blue mussels (Mytilus edulis). These findings conflict with assertions that tautog move to cooler water in summer when water temperatures reach 20 degree C. Tautog released at natural bedform sites were detected only at these sites throughout the study. Tautog released at manmade structures also displayed high site-utilization patterns, but several tautog periodically moved 2-10.2 km away from these sites over featureless bottom, a known deterrent to emigration for large temperate labrids in other waters. Benthic communities were similar at manmade sites and natural bedform sites, and movement away from manmade sites may have been influenced by habitat size as well as habitat structure. Understanding temporal and spatial utilization of habitats is an important first step to identifying essential fish habitat and to evaluating and protecting fishery resources within Chesapeake Bay and elsewhere.
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