THE BIOLOGY OF BLENNIUS PHOLIS L. (TELEOSTEI).

Abstract

Summary. The growth rate in B. pholis has been studied mainly from the zones on the otolith. One wide opaque zone and one narrower transparent zone are laid down during the course of a year. The transparent zones are formed in spring, from March to May, following a period of minimum sea temperatures, reduced food intake, maximum gonad development and no observed growth in length of the fish. The opaque zones are formed during the rest of the year, mainly during the summer period, to which the whole of the growth in length is confined. Seasonal size frequency distribution curves show distinct peaks which evidently correspond to two or three year classes, because they fall in close agreement with the lengths of these classes determined from direct otolith readings and from back calculations. Otoliths show slight negative heterogonic growth, which was allowed for in the back calculations. Both sexes show a similar growth rate and attain a similar longevity. Growth in length seems to occur mainly during summer in older age groups, but in the first year group it seems to continue at a reduced rate during autumn and winter. Growth is rapid during the first two years. It gradually decreases in subsequent years. This causes the older age groups to overlap considerably in size. A study of the seasonal changes in the gonads of B. pholis, based on an arbitrary classification of maturity, showed that both sexes mature when nearly two years old and begin to spawn when about 8 cm. in length. The males ripen earlier and remain ripe for a longer period than the females. Each individual spawns successively during the breeding season, which lasts from April to August. There is a quick recovery of the gonads in both sexes after spawning is over. Ripe fish occur throughout spring and summer but no spent females were seen until July. Eggs were found in abundance on the shore from mid‐April to mid‐August, with a maximum in June. Seasonal changes in gonad weight are less marked in males than in females. The ovaries reach their maximum weight during May, in preparation for maximum spawning, which occurs in June. In both sexes there is a regular seasonal cycle in the “condition factor” which cannot be explained as being due to seasonal changes in the gonad weight alone. Alternating periods of growth in weight and growth in length seem to account for most of the seasonal rise and fall in the condition factor. There is a temporary fall in February and March, which is probably due to net loss of reserves on account of reduced feeding at the coldest season. The mean K values obtained for each length group, from the pooled data of all seasons, gave no indication of the size at first maturity, but some evidence of this was obtained by separate treatment of the samples from the months when spent fish were abundant. The size frequency distributions of oocytes in ripening and ripe ovaries show multiple groups, which are successively ripened and shed during the breeding season. The food of Blennius pholis was investigated by the examination of the...

Homing in rocky intertidal fish. Are Lipophrys pholis L. able to perform true navigation?

“…Choosing and maintaining good shelters or nestling holes can be of primordial importance for adults during the reproductive season, and therefore, site fidelity to a known area may be selectively advantageous. Several studies report that during the breeding season while males guard nests, females search the area in an attempt to find appropriate nests or males for laying their eggs (Almada et al 1990b;Qasim 1957). The ability to use a spatial map of visual cues (e.g., topographic features) provides an advantage because it enables the fish to keep track of its position in a familiar area.…”

Temporal asymmetries in the feeding patterns along the tidal cycle in two sympatric littoral blennies

“…Both species feed mainly on gastropods, barnacles and algae, with a minor proportion of other invertebrates like amphipods, copepods and isopods (Qasim, 1957;Gibson, 1972;Milton, 1983;Monteiro et al, 2005). As suggested by Burrows et al (1999), these fish may be hungrier during the rising-tide, since in the previous tidal phase (low-tide) they have been confined to small refugia, like tide-pools and crevices, where the typical prey of both species (e.g.…”

“…When they are about 1 year old, L. pholis reach the upper size of adult C. galerita (Faria et al, 1996). At this stage L. pholis leaves the pools that are shared by the juveniles of both species, seeking new shelters in crevices and spaces under boulders, in the lower shore, where they hide in groups (Qasim, 1957;Gibson, 1972;Faria and Almada, 2001). This shift in low-tide shelter is accompanied by a shift in diet, the larger L. pholis now eating larger prey (Monteiro et al, 2005).…”

“…Qasim, 1957;Gibson, 1972;Milton, 1983;Faria et al, 2001), so little consideration has been given to the possibility that partitioning of resources among the two species may occur through spatial and temporal differences in behaviour during high-tide. Burrows et al (1999), using underwater TV observations, suggested that the shanny, Lipophrys pholis, shows the highest level of activity during the rising and high-tide periods, and that its feeding movements are concentrated around crevices.…”

Sex Ratio of Ribbonfish, Lepturacanthus Savala (Cuvier, 1829) From Karwar Waters, Karnataka

“…Sarojini (1957) [21] opinioned male and female fish congregate in separate schools while moving to the spawning grounds. Qasim, (1957) [24] suggested that the preponderance of one sex in a population is because of sexual difference in growth rate, the faster growth rate leads increasingly to the less loss from predator this influences the sex ratio.…”