Collection of juvenile mullet species from a brackishwater tidal farm in Nigeria

The major constraint to the development of aquaculture in Nigeria has been the non-availability of fingerlings in required numbers of cultivable species. A specifically designed trap to collect mullet (Liza falcipinnis; Liza grandisquamis) juveniles during high tides was successful in collecting juveniles year-round. The collectors was more successful during night spring tides than during neap tides or daytime collections. Thus, the use of traps, especially in the tidal zones, could provide a cost-effective method of stocking fish farms by collecting juveniles and seed from the natural environment.

Exotic species and genetically modified organisms in aquaculture and enhanced fisheries: ICLARM's position

This article contains a discussion paper on the use of exotic species and genetically modified organisms in aquaculture and enhanced fisheries, together with a summary of ICLARM's (International Center for Living Aquatic Resources Management, Philippines) current position on this important topic.

Life cycle and biological parameters of several Brazilian Amazon fish species

This contribution summarizes knowledge on the biology (population dynamics, reproduction, ecology) of 25 fish species from the Lower Amazon, Brazil, based on data from a Brazilian-German field project (IARA) and a review of the literature.

Deleterious effects of non-native species introduced into Lake Victoria, East Africa

Lake Victoria, in East Africa, has suffered from introductions and invasions of non-native species such as Lates niloticus, various tilapiine species, and Eichornia crassipes since the 1950s. These have had a devastating effect on the natural biological communities. This paper reviews the effects of the introductions on ecology, environment, fisheries and the local human population.

Length-weight relationships of five species of the family Sparidae in the Gulf of Guinea

Length-weight relationships are presented by sex and by country for five species of the family Sparidae (Pugrus caeruleostictus, Pagellus bellottii, Dentex canariensis, Dentex congonensis, Dentex angolensis) sampled in April 1990 during the Guinea '90 trawling survey off Sierra Leone, Liberia, Cote d'Ivoire and Ghana.

Comparative growth performance for species of the Family Clupeidae of Sierra Leone

Using length-frequency samples from the local fisheries and length-age data from otolith readings, von Bertalanffy growth parameters were estimated for the four species representing the Clupeidae family in Sierra Leone, Sardinella aurita, S. maderensis, Ethmalosa fimbriata and Ilisha africana showed the highest and lowest values of f, respectively, while Sardinella sp. were found to occupy the central position.

High level of hybridisation in three species of Indian major carps

Thirty individuals of each species of Indian major carps, i.e., Catla catla, Cirrhinus cirrhosus (C. mrigala) and Labeo rohita, obtained from a nursery near Mymensingh, Bangladesh were analysed by means of allozyme electrophoresis. Twenty-one loci were studied. Several loci revealed significant deviation from Hardy-Weinberg expectations caused by deficiency of heterozygotes, indicating Wahlund effects due to problems with species identification. Moreover, bimodal distributions of individual heterozygosity within the three putative species indicated hybridisation. This was confirmed using analysis of individual admixture proportions, as individuals misidentified to species and hybrids between species were observed. Furthermore, factorial correspondence analysis to visualize genetic relationships among individuals revealed three distinct groups containing misclassified individuals, along with some intermediate individuals interpreted as hybrids. Ten per cent of all C. catla and L. rohita had been erroneously identified to species, and 40 per cent of all presumptive C. catla were hybrids between C. catla x C. cirrhosus and C. catla x L. rohita. In the case of C. cirrhosus, 37 per cent of the samples were C. cirrhosus x L. rohita hybrids. Thirty per cent of all presumptive L. rohita turned out to be hybrids between L. rohita x C. catla and L. rohita x C. cirrhosus. The high incidence of hybrids in C. catla might be responsible for slower growth of the fish in aquaculture.

Biological parameters, body length-weight and length-height relationships for various species in Greek waters

Biological/fisheries parameters (L sub(oo) M, F) are presented for four fish species (Gadiculus argenteus; Gaidropsarus mediterraneous; Symphurus ligulatus; Lepidorhombus boscii) as well as body length-weight and length-height relationships for 11 and 12 fish species, respectively, estimated from trawl samples collected using three different cod-ends (stretched mesh size: 14 mm and 20 mm diamond-shaped and 20 mm square-shaped) during 1993-1994, in the western Aegean and North Euboikos Gulf, Greece. The fisheries paramaters, estimated from length-frequency using the ELEFAN approach and software, are discussed in the light of recent information on the selectivity of the presently used trawl cod-end (14 mm diamond shaped)

The role of small indigenous fish species in food and nutrition security in Bangladesh

In Bangladesh, only 6% of the daily food intake is animal food of which fish accounts for 50%. Rice is the mainstay, making up 60% of the daily food intake. However, many nutrients such as vitamins A and C, iron, calcium, zinc and iodine are not found in rice and have to be obtained from other sources. Small indigenous fish are a vital contribution to the diet of the rural poor in Bangladesh, where more than 30,000 children go blind every year from vitamin A deficiency and 70% of women and children are iron-deficient. Small fish, which are less than 10 cm in length and usually eaten whole with the organs and bones, contain large amount of calcium and possibly iron and zinc. The largest fish promoted in aquaculture do not contribute significantly to calcium intake. Some species also contain large amount of vitamin A. Much of the small indigenous fish (SIS) of Bangladesh are caught in floodplains and natural waterbodies. Small fish are eaten frequently in small amounts and are more equally distributed among family members than big fish of which men get the larger share. Unfortunately, overfishing and the deterioration of natural habitats have resulted in a decline in SIS. When measures are taken to improve food and nutrition security, there should be a focus on production of small fish so that greater quantities are accessible for consumption by the rural poor.

Food habits of two sciaenid fish species (Pseudotolithus typus and Pseudotolithus senegalensis) off Cameroon

Pseudotolithus typus and P. senegalensis (Sciaenidae) sampled off Cameroon Coast, West Africa, have been found to feed mainly on shrimps (Nematoplaemon hastatus and Parapenaeopsis atlantica) and juvenile fish (mostly clupeids). The diet composition is presented and discussed.

Comparison of average larval fish vertical distributions among species exhibiting different transport pathways on the southeast United States continental shelf

Water currents are vertically structured in many marine systems and as a result, vertical movements by fish larvae and zooplankton affect horizontal transport (Power, 1984). In estuaries, the vertical movements of larvae with tidal periods can result in their retention or ingress (Fortier and Leggett, 1983; Rijnsdorp et al., 1985; Cronin and Forward, 1986; Forward et al., 1999). On the continental shelf, the vertical movements of organisms interact daily and ontogenetically with depth-varying currents to affect horizontal transport (Pillar et al., 1989; Barange and Pillar, 1992; Cowen et al., 1993, 2000; Batchelder et al., 2002).

Mitochondrial gene sequences useful for species identification of western North Atlantic Ocean sharks

Molecular-based approaches for shark species identification have been driven largely by issues specific to the fishery. In an effort to establish a more comprehensive identification data set, we investigated DNA sequence variation of a 1.4-kb region from the mitochondrial genome covering partial sequences from the 12S rDNA, 16S rDNA, and the complete valine tRNA from 35 shark species from the Atlantic fishery. Generally, within-species variability was low in relation to interspecific divergence because species haloptypes formed monophyletic groups. Phylogenetic analyses resolved ordinal relationships among Carcharhiniformes and Lamniformes, and revealed support for the families Sphyrnidae and Triakidae (within Carcharhiniformes) and Lamnidae and Alopidae (within Lamniformes). The combination of limited intraspecific variability and sufficient between-species divergence indicates that this locus is suitable for species identification.

Courtship and spawning behaviors of carangid species in Belize

Many species of reef f ish agg regate seasonally in large numbers to spawn at predictable times and sites (Johannes, 1978; Sadovy, 1996; Domeier and Colin, 1997). Although spawning behavior has been observed for many reef fish in the wild (Wicklund, 1969; Smith, 1972; Johannes, 1978; Sadovy et al., 1994; Aguilar Perera and Aguilar Davila, 1996), few records exist of observations on the courtship or natural spawning for the commercially important family Carangidae (jacks) (von Westernhagen, 1974; Johannes, 1981; Sala et al., 2003). In this study, we present the first observations on the natural spawning behavior of the economically-valuable permit (Trachinotus falcatus)(Linnaeus, 1758) from the full to new moon period at reef promontories in Belize, with notes on the spawning of the yellow jack (Carangoides bartholomaei) (Cuvier, 1833), and the courtship of five other carangid species.

Ecosystem-based Management for Protected Species in the North Pacific Fisheries

In the North Pacific Ocean, an ecosystem-based fishery management approach has been adopted. A significant objective of this approach is to reduce interactions between fishery-related activities and protected species. We review management measures developed by the North Pacific Fishery Management Council and the National Marine Fisheries Service to reduce effects of the groundfish fisheries off Alaska on marine mammals and seabirds, while continuing to provide economic opportunities for fishery participants. Direct measures have been taken to mitigate known fishery impacts, and precautionary measures have been taken for species with potential (but no documented) interactions with the groundfish fisheries. Area closures limit disturbance to marine mammals at rookeries and haulouts, protect sensitive benthic habitat, and reduce potential competition for prey resources. Temporal and spatial dispersion of catches reduce the localized impact of fishery removals. Seabird avoidance measures have been implemented through collaboration with fishery participants and have been highly successful in reducing seabird bycatch. Finally, a comprehensive observer monitoring program provides data on the location and extent of bycatch of marine mammals and seabirds. These measures provide managers with the flexibility to adapt to changes in the status of protected species and evolving conditions in the fisheries. This review should be useful to fishery managers as an example of an ecosystem-based approach to protected species management that is adaptive and accounts for multiple objectives.

An Index of Abundance for Coastal Species of Juvenile Sharks from the Northeast Gulf of Mexico

A fishery-independent assessment of juvenile coastal shark populations in U.S. waters of the northeast Gulf of Mexico was conducted using two methods: gillnets and longlines. Surveys were conducted monthly during April–October in two fixed sampling areas from 1996 to 1998. The Atlantic sharpnose shark, Rhizoprionodon terraenovae, and the blacktip shark, Carcharhinus limbatus, were the most common species captured with either longlines or gillnets. An additional 14 shark species were captured, and juvenile indices of abundance were developed for 8 species with gillnets and 6 species of sharks with longlines. Trends in catch-per-unit-effort were found to vary depending on species. Length-frequency information revealed that the majority of sharks captured were juveniles. Given the direct relationship between stock and recruitment for sharks, continued monitoring of juvenile abundance will aid in determining the strength of the parental stock size and for predicting future population strength.