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Marine and fisheries research

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Research papers

1983 · Journal of Fish Biology · 65 citations

The biology of Carangidae (Teleostei) in Natal estuaries

The occurrence and abundance of 17 species of Carangidae in Natal estuaries are described. The following six species are of significance in the estuarine community: Caranx ignobilis, C. melampygus, C. papuensis, C. sexfasciatus, Lichia amia and Scomberoides lysan . Only juveniles and subadults utilize estuaries. The time of recruitment, growth rates and feeding biology of the six species were investigated. Among the juveniles, C. ignobilis and C. sexfasciatus are mainly piscivorous on a variety of small estuarine fishes and estuarine dependent juveniles of marine species, while C. melampygus, C. papuensis and S. lysan filter feed on mysids and juvenile penaeids. Subadults of all species are piscivorous, although C. papuensis and S. lysan retain a suitable gill raker structure for filter feeding and a proportion of their diet consists of mysids and penaeids. The salinity and turbidity preferences of each species were investigated. All are euryhaline but C. melampygus, C. papuensis and 5. lysan are only found in clear water. It is suggested that the more widespread estuarine distribution of juvenile C. sexfasciatus and C. ignobilis may be related to their turbidity tolerances. The role of carangids in Natal estuaries is discussed in relation to their ecological significance in estuaries as predators and their degree of estuarine dependence.

1978 · Journal of Fish Biology · 39 citations

Aspects of the biology of<i>Scomberomorus maculatus</i>(Mitchill) in Trinidad

A study was made of the biology of S. maculatus . Results of gonadal examination of 347 males and 409 females suggest spawning takes place from October to April, a period associated with low salinities. First spawning takes place at ages I1 and/or III for both sexes. Sex ratio results suggest spawning may be promiscuous, males outnumbering females. Egg counts from 12 ripe females ranged from 26 057 to 149 736. A period of abundance from May to September may be associated with a post‐spawning feeding migration encompassing the island, possibly in a clockwise direction. Otolith were used to age 817 fish. Opaque and translucent rings are formed yearly. The translucent ring, representing a period of slow growth, is laid down during the spawning season. The fish can live for nine years with females growing faster than males. Growth parameters are compared with those obtained for Brazilian and Florida fish. Mortality rates were investigated and gill nets effected higher mortality rates than beach seines. Full recruitment takes place at age III for gill nets, and ages II and III for beach seines.

2003 · Gulf and Caribbean Research · 27 citations

The Biology of Wahoo (Acanthocybium solandri) in the Western Central Atlantic

This contribution summarizes aspects of the biology of the wahoo, Acanthocybium solandri (Scombridae), that are pertinent to assessment and management of this species in the western central Atlantic (WCA). In this region wahoo is a target species for both commercial and recreational fisheries, and annual landings appear to have increased steadily over the last 30 years to in excess of 2000 mt. Wahoo is believed to be migratory, but little is known of the migration patterns. Significant seasonal variation in catches within the region indicates that it is seasonally abundant in most locations. Periods of peak abundance occur from the fall through spring in the southeastern and northern Caribbean islands, and are restricted to the warmer months (late spring through early fall) in the more northerly locations (northern Gulf of Mexico, North Carolina, and Bermuda). Wahoo exhibits early sexual maturity (within the first year) and a spawning season that extends from at least May to October. Females are multiple batch spawners and are highly fecund. Limited age and growth studies indicate that it is a relatively fast-growing species, has high mortality, and probably lives for 5-6 years. Wahoo is primarily piscivorous, although some invertebrates including squids are eaten. A relatively small number of parasite species have been associated with it. There is no evidence of more than a single shared stock of wahoo in the WCA, and recent genetic studies, using RAPD markers, suggest that stock boundaries may extend beyond this region. The status of the wahoo resource in the WCA remains unclear. Reliable wahoo catch and fishing effort data from the entire WCA, improved knowledge of migration patterns, reproductive characteristics and critical habitat (e.g., preferred spawning areas), validation of age, growth and mortality estimates, and a more comprehensive analysis of stock structure for the entire Atlantic are needed for informed wahoo stock assessment and management.

1965 · ICES Journal of Marine Science · 15 citations

The Biology of West African Polynemid Fishes

The biology of two commercially important polynemids has been studied over an eleven-month period on the trawling grounds off Lagos, Nigeria. One species, Pentanemus quinquarius (Bloch), has a normal bisexual reproductive cycle, but in the second species, Galeoides clecadactylus (L.), it was found that only about 25% of the females develop directly from a juvenile stage, the others developing female gonads by passage through a non-functional hermaphroditic stage arising in apparently normal males. Spawning occurs in all months in both species, the intensity being less cyclical in Pentanemus than in Galeoides, which peaks in the dry season and almost ceases spawning during the rainy season. Petersen growth rate studies show that Galeoides up to 3 years old are present in the catches, the values for von Bertalanffy parameters being K = 0·41 and L∞ = 54·5 cm; Pentanemus rarely survive their second year of life. Derivation of lengths at first maturity for Galeoides is complicated by the nature of the reproductive cycle and these range from 15 cm for males to 25·5 cm for secondary females; Pentanemus mature at less than six months old at about 15 cm. The implications of these biological data for the trawl fishery are considered and it is suggested that despite dependence on very few year-classes both species are responding relatively well to the present unregulated exploitation.