The schooling ethology of Lutianus monostigma (Pisces) in the shallow reef environment of Aldabra

Field observations on a school of Lutianus monostigma have been made off Aldabra in the shallow reef environment. The school does not exhibit any obvious response to temperature. The response to current is the main factor that determines school orientation and position in the channel. Longshore movements are performed but their function is not known. The morning and evening dispersal may be associated with changes in light intensity and/or the crepuscular feeding habits. The response to predators depends upon the behaviour of the predator, its species and size. Other factors affecting the school in their natural environment are described.     

Cleaner fish, Labroides dimidiatus, diet preferences for different types of mucus and parasitic gnathiid isopods

Cleaner fish, Labroides dimidiatus, prefer the mucus of the parrotfish, Chlorurus sordidus, to parasitic gnathiid isopods, the main items in their diet, indicating a major conflict between clients and cleaners over what the latter should eat during interactions. We tested whether the conflict varied with client species (and the quality of its mucus) and with the presence of blood in the gnathiids. First, we offered cleaners the choice between mucus of the parrotfish and that of the snapper, Lutjanus fulviflamma. When offered equal amounts of mucus on Plexiglas plates, cleaners readily developed a significant preference for the parrotfish mucus. Reducing the amount of parrotfish mucus by 75% made the preference disappear. In a second test, we offered the cleaners gnathiids that were or were not engorged with client fish blood. Cleaners showed no significant preference for either food item. Our results suggest that the degree of conflict between cleaners and clients may vary between species, depending on whether the latter have a preferred mucus. In contrast, the cleaners' lack of preference for engorged gnathiids benefits clients because it means that cleaners do not hesitate to eat unengorged gnathiids before the gnathiids harm the fish by removing blood or by transmitting blood parasites.     

Population ecology of the temperate reef fish Pseudolabrus celidotus Bloch & Schneider (Pisces: Labridae). I. Factors influencing recruitment

Recruitment of Pseudolabrus celidotus Bloch & Schneider was measured at 10 reef areas over four seasons (1977–1980) in north-eastern New Zealand. These encompassed six different habitat types, defined on the basis of their major physical and biological features. Recruitment differed among habitats and years, but spatial differences were more pronounced than temporal changes. Shallow broken rock (SBR) habitats dominated by macrophytic brown algae consistently had the highest recruitment. Six areas within SBR habitats were censused over three seasons (1979–1981). Even within this one habitat type, most of the variation in numbers was explained by spatial effects. Furthermore, the differences in recruitment between sites remained fairly constant because changes between years were similar in magnitude and direction.An adult removal experiment established that recruitment was independent of adult numbers. Macroalgae affected recruitment as was demonstrated by an algal removal experiment, which resulted in a marked reduction in recruitment, and an algal addition (via urchin removal) experiment which resulted in an increase. Juvenile densities increased as an exponential function of algal biomass per unit area, but the relationship was dependent on depth. Recruitment reached higher levels in shallow habitats (< 8 m) than deeper ones, despite a similar range of algal biomass.It is suggested that there are several factors operating at the time of or shortly after settlement, which result in spatial differences in recruitment on a very small scale. The observed temporal variation may be due to a different set of factors operating prior to settlement, and may have effects measurable over a considerably broader spatial scale.     

The feeding strategies of a facultative cleanerfish, Thalassoma bifasciatum (Pisces: Labridae)

The adult Bluehead wrasse (Thalassoma bifasciatum) is a facultative cleanerfish that can change its colouration into any one of three: patterns. These patterns correspond to several modes of feeding behaviour which, in turn, can be correlated with the movements of host fishes. The barred pattern occurred on individuals that are far ranging and also on those that formed unstable cleaning groups. These groups tended to form at locations having sharp drops in depth of several metres. Here these groups serviced large groups of host fishes. The striped pattern occurred on solitary individuals with a limited home range. They occurred in very shallow areas and serviced small groups of host fishes. The bright yellow pattern developed when a large food source was discovered and may be related to the attraction of conspecifics.     

Cleaning behaviour of the goldsinny (Pisces,Labridae) in Swedish waters

The goldsinny, $\text{Ctenolabrus}$$\text{rupestris}$, on the Swedish west-coast has been shown to be a facultative cleaner with the ballan wrasse, $\text{Labrus}$$\text{berggylta}$, as the cleanee. Twenty-four cleanings were observed during 1975 to 1981. The cleaning pattern of the symbiosis is described and the low rate of cleaners within the species is discussed.     

Effects of temperature and salinity on yolk utilization in Bairdiella icistia (Jordan & Gilbert) (Pisces: sciaenidae)

The effects of nine different combinations of temperature and salinity on yolk utilization in the eggs and larvae of the sciaenid fish, Bairdiella icistia (Jordan & Gilbert) have been investigated. The rate of yolk absorption was accelerated at higher temperatures, but salinity had only a slight effect. Increased water content resulted in larger yolk sacs at hatching in low salinities and at low temperatures. In all treatments, functional eyes and jaws were formed before the yolk had been completely exhausted. Yolk was utilized most efficiently at the intermediate temperature (24 °C) and lowest salinity (20 %.).     

The Lek-like Mating System of Halichoeres melanochir (Pisces: Labridae) at Miyake-jima,Japan1

Reproductive behavior and social organization of the labrid fish Halichoeres melanochir were studied at Miyake-jima, Izu Islands, Japan. ♂♂ set up contiguous territories from early to mid-afternoon daily during the breeding season, with ♂♂ at the center of the spawning site experiencing significantly higher spawning success than those at the periphery. Unlike other labrids with lek-like mating systems previously reported, H. melanochir is sexually monochromatic and shows only minimal sexual size-dimorphism. The spawning behavior and mating system are described and compared with current theories on labrid reproductive strategies.     

Distribution and tissue retention of cesium-134 and cobalt-6o in the nile catfish clarias lazera (cuv. & val.)

The Nile catfish, Clarias lazera was found to concentrate radioactive cesium-134 and cobalt-6o from the aquatic environment. For cesium-134 the rate of uptake increased by increase of exposure time, while for cobalt-6o maximum uptake occurred after one day of exposure. The corresponding concentration factors at maximum uptake levels were 0.37 and 0.36 for cesium and cobalt respectively.The internal distribution of these radionuclides in the different tissues and organs of the fish due to uptake from the aquatic environment followed the decreasing order:For ¹³⁴Cs: muscle, bone, gills, stomach, kidneys, intestine and liver.For ⁶⁰Co: bone, muscle, gills, intestine, kidneys, stomach and liver.The internal distribution due to ingestion of these radionuclides followed nearly the same order as was found in case of uptake from the aquatic environment.     

The predatory behaviour of Caranx melampygus (Pisces) in the channel environment of Aldabra Atoll (Indian Ocean)

Aspects of the predatory behaviour of free ranging Curanx melampygus have been examined in the shallow channel environment of Aldabra Atoll, Indian Ocean. Differences in the frequency of occurrence and number of fish hunting at two adjacent observation areas are described. The numbers of Caranx moving through the area appears to be influenced by tidal factors and possibly the abundance of prey and other environmental factors. The percentage offish hunting increases progressively throughout the day and is most commonly performed by solitary fish or small groups. While approximately equal numbers of Caranx move up or down stream significantly more fish engage in hunting activity when moving down stream which suggests the mechanical advantage of moving with the flow of water has advantages to the hunting fish. Several types of interspecific feeding association are described in which the Caranx is able to scavenge from others or to exploit the hunting methods of other species. More small Caranx form associations than do large Caranx . There is a relationship between the length of a hunting Caranx and the size and/or type of prey that makes an avoidance reaction to it. This relationship between different group sizes and the prey avoidance response is less clearly defined and it is suggested that whether hunting in groups or singly the final interaction is between a single predator and single prey. Ways by which group advantages may occur on grouped prey are described and are considered the result of independent individual action rather than group co-operation. Coastal observations indicate that Caranx use topographic features to shield their approach to areas of high prey density.     

Chromosomal analysis of repeated DNAs in the rainbow wrasse Coris julis (Pisces, Labridae)

Despite the interest of several authors, the karyotype of the labrid C. julis is still debated and in particular the presence of sex-chromosomes is still contradictory. In order to analyze the karyotype organization of C. julis we have performed an analysis with classical and molecular cytogenetic techniques. Our results after silver-, CMA₃- and DAPI-staining, C-banding and fluorescent in situ hybridization (FISH) using 28S rDNA, 5S rDNA, and telomeric repeat (TTAGGG) _n as probes allowed us to characterize the chromosomal location of several repetitive DNAs of C. julis. Finally, regardless of the technique used, no difference in the chromosome complement was found between males and females. This revised version was published online in August 2006 with corrections to the Cover Date.     

Benefits of heterospecific foraging by the Caribbean wrasse,Halichoeres garnoti (Pisces: Labridae)

Synopsis Terminal-phase yellowhead wrasses, Halichoeres garnoti, foraged alone or in association with foraging goatfish, Pseudupeneus maculatus and Mulloides martinicus. Whereas H. garnoti did not dig for benthic infauna, the goatfish foraged almost exclusively on and in sand substrata. Wrasses in the company of goatfish made significantly more strikes on sand substrata than did solitary wrasses, although there were no significant differences in the frequency of strikes on sand and hard substrata combined. The frequencies of other behaviors (searches, scratches, flights, chases, rests, yawns, and cleanings) were not significantly different between solitary and associated wrasses. H. garnoti are attracted to foraging goatfish, which provide access to an otherwise unavailable food resource. To whom reprint requests should be sent     

Courtship and Spawning Behavior in the California Sheephead, Semicossyphus Pulcher (Pisces: Labridae)

We recorded the courtship and spawning behavior of a protogynous fish, the California sheephead, Semicossyphus pulcher, throughout their spawning season at Bird Rock, Santa Catalina Island, California. We made additional observations at the Monterey Bay Aquarium and confirmed the details of behavior seen in the field. Large males held spawning territories in which females congregated approximately 1 h before sunset. Courtship commenced shortly before sunset and involved the male approaching each female, making lateral contact and leading her in a circular pattern. Smaller males attempted to court females within the territories, prompting large males to abort spawns and engage in chasing behavior with small males. Females visited several territorial males throughout the day, indicating that they are not part of a strict harem. Both field and aquarium observations confirm that the mating system can be successfully predicted from the size advantage model. Current regulations on the sheephead fishery, which allow for the removal of large, rare males, could have significant effects on the social structure, reproductive output, and mating processes of local populations. Moreover, understanding the mating system of the California sheephead illustrates the need for creating management strategies that better complement the unique life histories of marine fishes with alternative reproductive strategies.     

Phenotypic plasticity in the reef corals Montastraea annularis (Ellis & Solander) and Siderastrea siderea (Ellis & Solander)

Mature colonies of Montastraea annularis (Ellis & Solander) and Siderastrea siderea (Ellis & Solander) were transplanted reciprocally between four reef environments near Discovery Bay, Jamaica. Multivariate analyses of variables describing corallite structures show that colonies of M. annularis change their skeletal morphology after transplantation from that characteristic of their original habitat to that characteristic of the environment to which they were moved. Control colonies of M. annularis, however, retain the morphology characteristic of their original habitat after manipulation. Many colonies of S. siderea similarly altered their morphology after transplantation, but some retained the morphology characteristic of their original habitat. Most control colonies of S. siderea did not change after manipulation. In general, control colonies of S. siderea show more morphologic variation between skeleton deposited before and after manipulation within colonies and also between colonies within populations, than did control colonies of M. annularis.These results indicate that, although M. annularis shows more plasticity than S. siderea. both species have highly plastic phenotypes. A large number of characters describing the architecture of corallites respond to environmental factors such as light intensity, sedimentation rate, water activity, and food availability. The most plastic characters in M. annularis describe coenosteal features and the thickness of thecae. The most plastic characters in S. siderea describe the thicknesses of thecae. septa, and columellae.This study suggests that phenotypic plasticity is an important species attribute in scieractinians and may be a significant mechanism in controlling the distribution and abundance of scleractinians on reefs.     

The ontogeny of agonistic behaviour in the blue gourami, Trichogaster trichopterus (Pisces,Anabantoidei)

The development of agonistic behaviour in the blue gourami, Trichogaster trichopterus, was studied from hatching to four months of age. Larval motor patterns appear first as simple, uncoordinated, and irregular movements and gradually become regular and well coordinated, forming integrated complex patterns, such as swimming, surfacing, and feeding. Most motor patterns used in agonistic interactions are first exhibited in non-social contexts. Initial interactions between young fish consist of Approach and investigation in a feeding context, in some cases followed by nibbling, Biting, and Chasing by one fish. Later, initial Approaches are separated from Biting and Chasing by Lateral Displays, circling, Tail Beating, and Fin Tugging, and by Appeasement behaviour that inhibits Chasing and Biting by the opponent.Agonistic behaviour of socially isolated fish, when paired in dyadic encounters as adults, indicates that the role of social experience as an integrator and regulator of social behaviour may change progressively during development and become more important as ontogeny proceeds.