The abiotic ecology of breeding ground of Palaemonid prawns in the Ilaje Estuary, Ondo State, Nigeria

In situ ecological assessment of the breeding grounds of palaemonid prawns was conducted in some selected locations around Ondo state coastal area between the months of April and September. Data obtained were subjected to both descriptive and inferential statistics. Three species of Palaemonid prawns were identified in four different locations within the study area with relative abundance ratio of 4:3:1. Macrobrachium macrobrachion, Nematopalaemon hastatus and Palaemon maculatus respectively. Sex ratio of 1 male to 5 females for M. macrobrachion, and 1 male to 2 females for N. hastatus and P. maculatus were observed with result showing significant relationships (P < 0.05) in distribution patterns across collection sites. Population distribution within the water column showed that palaemons are sub-lithoral prawns inhabiting maximum mean depth of 0.67m ± 0.025. Surface macro-phytes such as Eichhornia crassipies, Paspalum vaginatum, and Pistia stratiotes are common providing hiding spots for the prawn at the breeding ground. The mean soil pH across the sites stands at 6.67± 0.399 with the soil textural class that range from silty-loam to silty-clay. Also, the water quality parameters of study areas suggest that captive culture and rearing of Palaemons may be feasible outside the breeding areas.

Variability in supply and cross-shelf transport of pink shrimp (Farfantepenaeus duorarum) postlarvae into western Florida Bay

The variability in the supply of pink shrimp (Farfantepenaeus duorarum) postlarvae and the transport mechanisms of planktonic stages were investigated with field data and simulations of transport. Postlarvae entering the nursery grounds of Florida Bay were collected for three consecutive years at channels that connect the Bay with the Gulf of Mexico, and in channels of the Middle Florida Keys that connect the southeastern margin of the Bay with the Atlantic Ocean. The influx of postlarvae in the Middle Florida Keys was low in magnitude and varied seasonally and among years. In contrast, the greater postlarval influx occurred at the northwestern border of the Bay, where there was a strong seasonal pattern with peaks in influx from July through September each year. Planktonic stages need to travel up to 150 km eastward between spawning grounds (northeast of Dry Tortugas) and nursery grounds (western Florida Bay) in about 30 days, the estimated time of planktonic development for this species. A Lagrangian trajectory model was developed to estimate the drift of planktonic stages across the SW Florida shelf. The model simulated the maximal distance traveled by planktonic stages under various assumptions of behavior. Simulation results indicated that larvae traveling with the instantaneous current and exhibiting a diel behavior travel up to 65 km and 75% of the larvae travel only 30 km. However, the eastward distance traveled increased substantially when a larval response to tides was added to the behavioral variable (distance increased to 200 km and 85% of larvae traveled 150 km). The question is, when during larval development, and where on the shallow SW Florida shelf, does the tidal response become incorporated into the behavior of pink shrimp.

Common carp (Cyprinus carpio) breeding in Nigeria

The development of the common carp (Cyprinus carpio) breeding programs in Nigeria is discussed.

Stock evaluation and development of a breeding program for common carp (Cyprinus carpio) in Karnataka, India: progress of a research project

Common carp (Cyprinus carpio) is the single most important species for aquaculture in the state of Karnataka, India, where it is generally grown in polyculture with Indian major carps. Precocious maturation and unwanted reproduction in the species have been identified as constraints to increase production in aquaculture and culture-based fisheries in Karnataka state. Stocks of C. carpio obtained from Hungary (Amur and P3), Indonesia (Rajdanu) and Vietnam (SV) are being assessed alongside two local stocks (L-BRP and L-FRS) in a series of culture performance trials with the objective of setting up a base population for selective breeding. The paper presents progress of research being undertaken at the Fisheries Research Station, University of Agricultural Sciences, Bangalore, India.

Some reproductive aspects of Chrysichthys nigrodigitatus (Lacépède) from Cross River, Nigeria

Between May and October 1990, fecundity, egg size and condition factor of Chrysichthys nigrodigitatus (Lacépède) in the Cross River, Nigeria, were studied. The fecundity (F) of this population varied from 3 046 eggs (total length, L=28.5 cm) to 28 086 eggs (L=64 cm). A mean relative fecundity of 231 eggs/cm or 13 eggs/g of fish was obtained for this population. The fecundity of this population can be estimated with the formula F=2.511 · L 2.30 or F=52.893 · W 0.78 , total length being in cm and weight (W) in g. The mean egg diameter of this population varied from 0.65 mm to 3.54 mm. Condition factor (CF) of the population varied from 0.24 to 1.34 with 0.977 as the mean; 52.8% had CF higher than the mean and 47% had CF above unity. Smaller fish in this population were in better condition than bigger ones. The egg size and condition factor obtained in this study are evidence that the Cross River population of C. nigrodigitatus can provide excellent broodstock.

Approaches to national fish breeding programs: pointers from a tilapia pilot study

Details are given of a framework for developing breeding programmes using experience from the Genetic Improvement of Farmed Tilapias project which focussed on Nile tilapias (Oreochromis niloticus ). The following aspects are outlined: Analysis of targeted production and marketing systems; Breeding goals; Systematic documentation and evaluation of available genetic resources and choice and genetic base; Number of strains; Breeding strategy; Selection criteria and evaluation; Production and dissemination of improved strains; and, social, economic and environmental impacts.

Breeding and propagation of tilapia (Oreochromis niloticus) in a floating hatchery, Gabon

Based on the encouraging results obtained by earlier workers, the concept for a floating hatchery was developed for producing tilapia for both farming and enhanced fisheries in the freshwater lakes and coastal lagoons of Gabon. The research and development work to test this concept was undertaken with Nile tilapia (Oreochromis niloticus). Two places in Gabon were selected, representing climatic and environmental condition similar to other parts of the country. The study aims to improve fish production in the freshwater lakes of the Lambarene area, and in the numerous coastal lagoons of Gabon, to compensate for the current overexploitation of natural stocks, or the alternative of introducing other species, and to reduce the drift of fishing population away from lakes.

Genetic diversity and selective breeding of red common carps in China

China has a very rich genetic diversity in common carp (Cyprinus carpio) and the red common carp plays an important role in Chinese aquaculture and genetic studies. Selective breeding, particularly crossbreeding has been applied successfully to red common carps in China, and the products of these efforts have been in commercial use since the 1970s. However, knowledge of the quantitative and molecular genetics of these carps is limited. Studies were therefore undertaken to: (1) understand the genetic diversity and genetic relationship of red common carps in China; (2) understand the inheritance of color phenotype of Oujiang color carp; (3) select stable Oujiang color carp with fast growth rate and ornamental Oujiang color carp comparable with the Koi common carp from Japan; (4) study the culture performance and culture systems suitable for the Oujiang color carp in cages and paddies; (5) extend better quality fish and appropriate culture systems for small scale fish farmers in poor areas.

Tilapia breeding in ricefields in Vietnam

Results of the studies undertaken for breeding and nursing Nile tilapia (Oreochromis niloticus) in ricefields in Thai Binh province in Vietnam during the years 1995-96 are briefly presented in this paper.

Perspectives from agriculture: advances in livestock breeding - implications for aquaculture genetics

In this paper we present livestock breeding developments that could be taken into consideration in the genetic improvement of farmed aquaculture species, especially in freshwater fish. Firstly, the current breeding objective in aquatic species has focused almost exclusively on the improvement of body weight at harvest or on growth related traits. This is unlikely to be sufficient to meet the future needs of the aquaculture industry. To meet future demands breeding programs will most likely have to include additional traits, such as fitness related ones (survival, disease resistance), feed efficiency, or flesh quality, rather than only growth performance. In order to select for a multi-trait breeding objective, genetic variation in traits of interest and the genetic relationships among them need to be estimated. In addition, economic values for these traits will be required. Generally, there is a paucity of data on variable and fixed production costs in aquaculture, and this could be a major constraint in the further expansion of the breeding objectives. Secondly, genetic evaluation systems using the restricted maximum likelihood method (REML) and best linear unbiased prediction (BLUP) in a framework of mixed model methodology could be widely adopted to replace the more commonly used method of mass selection based on phenotypic performance. The BLUP method increases the accuracy of selection and also allows the management of inbreeding and estimation of genetic trends. BLUP is an improvement over the classic selection index approach, which was used in the success story of the genetically improved farmed tilapia (GIFT) in the Philippines, with genetic gains from 10 to 20 per cent per generation of selection. In parallel with BLUP, optimal genetic contribution theory can be applied to maximize genetic gain while constraining inbreeding in the long run in selection programs. Thirdly, by using advanced statistical methods, genetic selection can be carried out not only at the nucleus level but also in lower tiers of the pyramid breeding structure. Large scale across population genetic evaluation through genetic connectedness using cryopreserved sperm enables the comparison and ranking of genetic merit of all animals across populations, countries or years, and thus the genetically superior brood stock can be identified and widely used and exchanged to increase the rate of genetic progress in the population as a whole. It is concluded that sound genetic programs need to be established for aquaculture species. In addition to being very effective, fully pedigreed breeding programs would also enable the exploration of possibilities of integrating molecular markers (e.g., genetic tagging using DNA fingerprinting, marker (gene) assisted selection) and reproductive technologies such as in-vitro fertilization using cryopreserved spermatozoa.

Preliminary results of a silver carp breeding program in Vietnam

The article describes the silver carp (Hypophthalmichthys harmandi and Hypophthalmichthys molitrix) breeding program in Vietnam.

Low cost breeding and hatching techniques for the catfish (Heteropneustes fossilis) for small-scale farmers

The high demand for the stinging catfish (Heteropneustes fossilis) and declining wild stocks led the Centre for Aquaculture Research and Extension of India to look for methods for the culture of the species. This paper presents a low-cost, simple breeding technique developed and tested by the Centre that can be easily adopted by rural farmers.

Cross-shelf and seasonal variation in larval fish assemblages on the southeast United States continental shelf off the coast of Georgia

Seasonal and cross-shelf patterns were investigated in larval fish assemblages on the continental shelf off the coast of Georgia. The influence of environmental factors on larval distributions also was examined, and larval transport processes on the shelf were considered. Ichthyoplankton and environmental data were collected approximately every other month from spring 2000 to winter 2002. Ten stations were repeatedly sampled along a 110-km cross-shelf transect, including four stations in the vicinity of Gray’s Reef National Marine Sanctuary. Correspondence analysis (CA) on untransformed community data identified two seasonal (warm weather [spring, summer, and fall] and winter) and three cross-shelf larval assemblages (inner-, mid-, and outer-shelf ). Five environmental factors (temperature, salinity, density, depth of the water column, and stratification) were related to larval cross-shelf distribution. Specifically, increased water column stratification was associated with the outer-shelf assemblage in spring, summer, and fall. The inner shelf assemblage was associated with generally lower temperatures and lower salinities in the spring and summer and higher salinities in the winter. The three cross-shelf regions indicated by the three assemblages coincided with the location of three primary water masses on the shelf. However, taxa occurring together within an assemblage were transported to different parts of the shelf; thus, transport across the continental shelf off the coast of Georgia cannot be explained solely by twodimensional physical factors.