Ballan Wrasse Labrus Bergylta Research Articles

Gender distribution, sexual size dimorphism and morphometric sexing in ballan wrasse Labrus bergylta.

In wild ballan wrasse Labrus bergylta, mass-length relationships were not different between genders, and positive allometry was found in the mixed-gender population. Male-biased sexual size dimorphism was significant and the most effective morphometric method for sexing L. bergylta outside of the species spawning window used body mass (M(B) in g), total body length (L(T) in mm) and Fulton's condition factor (K) as discriminant variables to predict gender with 91% accuracy. The discriminant score (S(D)) of a specimen can be calculated as S(D) = 0.01 M(B)- 0.016 L(T)- 3.835 K + 6.252 to predict its gender as female or male if S(D) is < 1.459 or S(D) is > 1.504, respectively. There was a potential trend towards earlier sexual inversion compared to previous studies at comparable latitudes. Sex change is a phenotypically plastic trait under social control in haremic fishes and should be monitored in increasingly exploited L. bergylta.

Restoration of a Temperate Reef: Effects on the Fish Community

The extraction of large boulders from coastal reefs for construction of harbours and coastal protection has led to habitat degradation for local fish populations through the destruction of cavernous reefs and changes in macroalgal cover resulting from a loss of substrate. The temperate reef at L?s? Trindel in Kattegat, Denmark, has now been re-established with the aim of restoring the reef’s historical structure and function. The effects of the restoration on the local fish community are reported here. Fishing surveys using gillnets and fyke nets were conducted before the restoration (2007) and four years after the restoration of the reef (2012). Species of the family Labridae, which have a high affinity for rocky reefs, dominated both before and after the restoration. Commercially important species such as cod Gadus morhua, and saithe Pollachius virens, occurred infrequently in the catches in 2007 but were significantly more abundant in the catches in 2012. Cods were especially attracted to the shallow part of the reef that was restored by adding stones. For some species, such as ballan wrasse Labrus bergylta, and cod, the proportion of larger individuals increased after the restoration. The findings highlight the importance of reef habitats for fish communities and the need for their protection.

Energy allocation and reproductive investment in a temperate protogynous hermaphrodite, the ballan wrasse Labrus bergylta

Energy allocation is an important component of life-history variation since it determines the tradeoff between growth and reproduction. In this study we investigated the state-dependent and sex-specific energy allocation pattern and the reproductive investment of a protogynous hermaphrodite fish with parental care. Individuals of Labrus bergylta, a temperate wrasse displaying two main different colour patterns (plain and spotted), were obtained from the fish markets in NW Spain between 2009 and 2012. Total energy of the gonad, liver, mesenteric fat and muscle (obtained by calorimetric analysis) and gut weight (as a proxy of feeding intensity) were modelled in relation to the reproductive phase of the individuals. A decrease in the energy stored as mesenteric fat from prespawning to spawning paralleled the increase in the gonad total energy in the same period. The predicted reduction in stored total energy over the reproductive cycle was higher than the energy required to develop the ovaries for the full range of female sizes analysed, suggesting a capital breeding strategy. Males stored less energy over a season and invested fewer resources in gamete production than females. Reproductive investment (both fecundity and energy required to produce the gonads) was higher in plain than in spotted females, which is in agreement with the different growth patterns described for the species.

Demographic Variation between Colour Patterns in a Temperate Protogynous Hermaphrodite, the Ballan Wrasse Labrus bergylta

Fish populations are often treated as homogeneous units in typical fishery management, thereby tacitly ignoring potential intraspecific variation which can lead to imprecise management rules. However, intraspecific variation in life-history traits is widespread and related to a variety of factors. We investigated the comparative age-based demography of the two main colour patterns of Labrus bergylta (plain and spotted, which coexist in sympatry), a commercially valuable resource in the NE Atlantic. Individuals were aged based on otolith readings after validating the annual periodicity of annuli deposition. The relationships between the otolith weight and fish age and between otolith length and fish length were strong but differed between colour patterns. The fit of the growth models to the age and length data resulted in divergent growth curves between colour morphotypes and between sexes. Males and spotted individuals attained larger mean asymptotic sizes (Linf) than females and plain individuals, respectively, but converged to them more slowly (smaller k). Estimates of mortality based on catch curves from two independent datasets provided a global total mortality (Z) of 0.35 yr–1, although Z was larger in plain and female individuals. Overall, the results of this research have direct implications for management of L. bergylta and, as a precautionary measure, we recommend considering both colour patterns as two different management units.

Natural sex change in the temperate protogynous Ballan wrasse Labrus bergylta

Wild Ballan wrasse Labrus bergylta were sampled monthly over 2 years in western Norway to identify the natural process of sex change in this species. Light microscopy of standard histological-stained and immunohistochemistry-treated gonad tissue showed that spermatogonial germ cells tended to proliferate around the periphery of the lamellae before filling into the slowly receding, apoptotic central areas of the lamellae. Sex change occurred following the breeding season. From July to September, fish were most often in an early state of gonadal transition (ET), characterized by degenerating previtellogenic oocytes and pockets of proliferating spermatogonia in the germinative epithelia. The majority of fish with late transitional gonads, that were typically dominated by spermatogenic cells, developing efferent ducts and the beginning of lobule formation, were found between October and November. Sex steroid profiles of fish representing the different sexual phases showed that breeding females had the highest concentrations of 17β oestradiol (E2 ) and the lowest concentration of 11 ketotestosterone (11KT). Concentrations of E2 decreased greatly in ET fish at the beginning of sex change and remained low in all subsequent phases. The opposite trend was demonstrated in 11KT profiles. Initial-phase female fish had minimal concentrations of 11KT, but these increased during subsequent transitions. Sex change occurred most often in fish 34-41 cm total length (L(T)) and the median of fish in the size-frequency overlap of female and male fish was 36 cm L(T).

Phylogeographic structure of a protogynous hermaphrodite species, the ballan wrasse Labrus bergylta, in Ireland, Scotland, and Norway, using mitochondrial DNA sequence data

AbstractD'Arcy, J., Mirimin, L., and FitzGerald, R. Phylogeographic structure of a protogynous hermaphrodite species, the ballan wrasse Labrus bergylta, in Ireland, Scotland, and Norway, using mitochondrial DNA sequence data. – ICES Journal of Marine Science, 70: 685–693. The ballan wrasse, Labrus bergylta, is a protogynous hermaphrodite marine fish species that inhabits coastal waters of the eastern North Atlantic. Sequential hermaphrodite species tend to be characterized by a skewed sex ratio, which is thought to lead to marked population structuring due to a reduced effective number of breeders. Furthermore, due to its large body size (compared with other wrasse species) and its peculiar feeding behaviour, this species has been identified as a candidate cleaner fish to be used in parasite control of farmed finfish. In the present study, we used mitochondrial DNA (control region) sequence data to investigate the genetic diversity and population structuring of ballan wrasse in waters around the British Isles and southern Norway. Ballan wrasse in southern Norway showed lower levels of genetic diversity than around the British Isles, which appear to be the result of historical demographic events (population bottleneck followed by expansion). Analysis of mismatch distributions and the presence of two highly divergent clades unevenly represented in Atlantic and Scandinavian regions suggest distinct recolonization patterns in these two regions. These results provide a first insight on the status of wild populations of ballan wrasse in the eastern North Atlantic, with implications for conservation and management.

Embryonic development in ballan wrasse Labrus bergylta

Eight primary embryonic developmental stages were assigned to eggs of ballan wrasse Labrus bergylta using key morphological features following standardized nomenclature: Ia, Ib, II, III, IV, V, VI and VI+, reared from single family clutches under comparable environmental conditions in Ireland and Norway. Development in L. bergylta is typical of demersal marine finfish species with a short egg stage. Hatching occurred c. 123 h post-fertilization (hpf) equivalent to 62·5 degree days at 12·2 ± 1·10° C (mean ±S.D.), after which the larvae swam intermittently near the surface of the water column.

The reproductive cycle of female Ballan wrasse Labrus bergylta in high latitude, temperate waters

This 2 year study examined the reproductive cycle of wild female Ballan wrasse Labrus bergylta in western Norway as a precursor to captive breeding trials. Light microscopy of ovarian histology was used to stage gonad maturity and enzyme-linked immuno-absorbent assay (ELISA) to measure plasma concentrations of the sex steroids testosterone (T) and 17beta-oestradiol (E(2)). Ovarian recrudescence began in late autumn to early winter with the growth of previtellogenic oocytes and the formation of cortical alveoli. Vitellogenic oocytes developed from January to June and ovaries containing postovulatory follicles (POF) were present between May and June. These POF occurred simultaneously among other late maturity stage oocytes. Plasma steroid concentration and organo-somatic indices increased over winter and spring. Maximal (mean +/-s.e.) values of plasma T (0.95 +/- 0.26 ng ml(-1)), E(2) (1.75 +/- 0.43 ng ml(-1)) and gonado-somatic index (I(G); 10.71 +/- 0.81) occurred in April and May and decreased greatly in July when only postspawned fish with atretic ovaries occurred. Evidence indicates that L. bergylta are group-synchronous multiple spawners with spawning occurring in spring and peaking in May. A short resting period may occur between late summer and autumn when previtellogenic oocytes predominate and steroid levels are minimal.

New Information on the Hosts and Distribution of the Marine Fish Leeches Trachelobdella Lubrica and Pontobdella Muricata (Clitellata, Hirudinida)

New Information on the Hosts and Distribution of the Marine Fish LeechesTrachelobdella LubricaandPontobdella Muricata(Clitellata, Hirudinida)Fish leeches collected in the Aegean Sea, the Sea of Marmara and the Black Sea were examined.Trachelobdella lubrica(Grube, 1840) was recorded for the first time from the ballan wrasseLabrus bergylta(Osteichthyes, Labridae), marine breamDiplodus vulgaris(Osteichthyes, Sparidae) and the grouperEpinephelus aeneus(Osteichthyes, Serranidae) from aquiculture. The leeches of this species were found in the Aegean Sea and the Sea of Marmara on the body surface, in the mouth and gill cavities of their hosts. Leeches identified asPontobdella muricata(Linnaeus, 1758) were collected from the thornback rayRaja clavata(Chondrichthyes, Rajidae) in the Black Sea.

Underwater television observations of Serpula vermicularis (L.) reefs and associated mobile fauna in Loch Creran, Scotland

The behaviour of Serpula vermicularis reef worms and associated mobile fauna in Loch Creran, on the west coast of Scotland, was recorded for six weeks using underwater television. The reef worms were extended almost continually, generally only retracting when stimulated by the close proximity of a predator. The length of hiding time varied according to the species triggering the reaction. The mean length of time retracted was 21 s. Fauna associated with the reefs included the corkwing wrasse Crenilabrus melops, ballan wrasse Labrus bergylta, black squat lobster Galathea squamifera and velvet swimming crabs Necora puber. There were few significant associations between tidal cycle and the presence/activity of associated fauna but a number of fish and crustacean species appeared to be influenced by the diurnal cycle. Gobies were recorded during daylight only with peak observations around midday while wrasse, butterfish Pholis gunnellus and cod Gadus morhua were crepuscular. The dawn and dusk appearance of juvenile cod in large shoals is suggestive of a nightly migration.

The Food of Post-Larval Fish. No. II (1918)

Investigation of the food of larval and post-larval fish from the townets has been continued throughout the year (1918) in the same way as previously, by examining the contents of stomach and intestine in the fresh state. From May 24th a new big net made of stramin, with a wooden frame 36 inches by 25 inches, was used in addition to the ordinary tow-nets. Any live specimens, and these were chiefly caught in the big net, were kept in small aërated aquaria standing in running water and fed with plankton in order to see, when possible, what food they ate. In this way a few post-larval fish went through the metamorphosis into the adult form. Details of these will be found in another paper in the same number of the Journal (page 9).The tow-nettings were regularly examined by Miss Webb in order to see whether the fish were feeding on what was commonest at the moment, and this was found to be usually the case, so far as the Copepods were concerned, although most of the young fish seemed to select their food to a certain extent. In any month the Copepods which are at that time commonest in the plankton are those most eaten by the young fish, but most of them have preferences and select in various degrees. Thus in June Calanus finmarchicus and Acartia clausi were the commonest Copepods, Temora longicornis coming next, Pseudocalanus elongatus and Oithona similis not occurring so frequently. The commonest young fish in the tow-nets in the same month were the Whiting, Pollack, Rockling and Ballan Wrasse (Labrus bergylta).