Aquaculture of the mangrove red snapper

Mangrove red snapper (Lutjanus argentimaculatus) is an important marketable species throughout the Indo-Pacific region. It is a euryhaline species; it can tolerate freshwater, brackishwater and marine water. Modular culture is the common system in snapper production in the Philippines. Stocking density is 4,000 fry per cropping; there could be 2 croppings per year. Brief details are given of investment costs and returns for culture in brackishwater pens.

The technology of milkfish hatchery in Indonesia

The culture of milkfish (Chanos chanos), which is the oldest fish cultured in Indonesia, has spread to almost all the provinces in the country. In order to answer the demand of milkfish fry, without decreasing production and wild fry supply, artificial fry production in big and small-scale hatcheries is being practiced. Details are given of the milkfish hatchery system, listing also the major criteria to be taken into account for site selection. Operation of the hatchery is described, outlining the following activities: broodstock rearing; hormone implantation; broodstock maintenance; egg production and harvest; and, larval rearing.

The natural life history of milkfish

Following brief descriptions of the various phases in the natural life history of the milkfish (Chanos chanos), namely adults, eggs and embryos, larvae, fry and metamorphosis, juveniles and sub-adults, a summary is provided of the life history, providing also a schematic diagram.

AQD's breeding-hatchery techniques

Details are given of standardized methods used by AQD for the spawning of seabass (Lates calcarifer) and the rearing of fry in the hatchery.

Preliminary observations on cage culture of Tilapia esculenta Graham and Tilapia xillii (Gervais) in Lake Victoria waters, at the Freshwater Fisheries Institute, Nyegezi, Tanzania

Cage culture of Tilapia is not suggested as a substitute for any known techniques in fish culture, but as one of the various techniques of obtaining more fish under controlled conditions. This fact has been very well accepted in various countries. Whererever facilities exist, this line of fish culture should be vigorously explored as a possible avenue in increasing fish production. High density stocking, management under controlled conditions, easy technique of fabricating the cage at relatively low cost, having no demand on land area, absence of prolific and effective breeding and easy availability of fish when a person needs it are a few of the attractions of the technique. The studies indicate that it is desirable to have different meshes for the cages, such as, small meshed cages for rearing fry to fingerlings stages, and larger meshed cages for rearing fingerlings to table sized fishes. II' the meshes are small, the resistance will be more and less water wilt pass through. While feeding with powdered food material, because of brisk activity of feeding fish, a part of the feed appeared wasted. This can be easily overcome if we would resort to feeding fish with cheap pelleted feeds which will no doubt reduce wastage. Precaution has to be taken against damage of the net and thereby loss of fish and against poaching by unauthorised persons. In the present attempt has been demonstrated the possibility of utilizing locally available species of Tilapia for cage culture and obtaining moderately satisfactory growth rates.

Hybridization between Tilapia zillii (Gervais) and Tilapia andersonii (Casteinau) at the Freshwater Fisheries Institute, at Nyegezi, Tanzania

As a part of an overall project on fishculture development techniques in Tanzania, hybridization between Tilapia zillii and Tilapia andersonii was carried out at the Freshwater Fisheries Institute, Nyegezi, Tanzania. T. andersonii, a plankton feeder, is not indigenous to Tanzania but was introduced in 1968 from Zambia for certain specific purpose. T. zillii, a macrovegetation feeder, is present locally and is common. In the present studies T. zillii (245.0 mm/260.0 g) female was hybridized with T. andersonii (288.0 mm/350.0 g) male. Under cement cistern conditions it was only after about four months of acclimatization that hybridization between the two occurred. About 1,637 interspecific hybrid fry were produced in a single brood. Eggs were adhesive and parental care shown by the female, the male being driven away. Growth under cistern conditions was slow, attaining a size of 134.8 mm/44.3 g in 10 months. But this growth rate need not be taken as ideal. In body shape, colouration and other morphometric characters the hybrids had inherited from both parents. The number of gill rakers among the hybrids was eighteen which was intermediate between T. zillii (12) and T. andersonii (27). Among one hundred and seventy two specimens (106.0 mm - 168.0 mm) cut and examined the sex ration was hundred per cent males and all of them were between II and IV stages of maturity. This is the first report of fish hybridization from Tanzania and possibly the first report on hybridization between T. zillii and T. andersonii. The full significanoe of the findings and its role in African fishculture is discussed.

Studies on induced breeding of Clarias gariepinus (Burchell, 1822) in hapa pens

Induced breeding of Clarias gariepinus was conducted monthly in hapa pens, set up in Otamiri river for nineteen months (June 1993 - December 1994). Results of natural fertilization were unsatisfactory as few eggs were fertilized. Mean relative fecundity, percentage fertilization, percentage hatching and percentage fry survival were: 15.86 ± 1.95 x 10', 18.92 ± 5.28%, 13.50 ± 3.8% and 6.42 ± 0.72%. Results from artificial fertilization were as follows: Mean relative fecundity, 13.80 ± 2.85 x 10', percentage fertilization, 81.91 ± 2.28%, percentage hatching, 86.10 ± 2.46% and percentage fry survival, 21.40 ± 1.89% respectively. The success of artificial fertilization depended largely on the latency period of 9-11 hours and this suggests that induced breeding in pens is feasible. The poor results from natural fertilization were attributed to lack of adequate substrate for the male fish to display courtship and subsequent fertilization of eggs.

Culturing the African lungfish in Uganda: effects of exogenous fish feed on growth performance in tanks

The availability of African lungfish (Protopterus aethiopicus) in many communities in Uganda is declining. Indigenous efforts to culture this fish usually produce poor yields and depend on feeding fish fry, minced meat, and leftover food. This study evaluates three formulated diets (diet-1, diet-2, diet-3) fed to wild caught lungfish fingerlings reared in indoor tanks for 77 days. Experimental fish gradually accepted sinking pellets, and marginal increases in average body weight were observed. Mean (± SE) final weight (15.86 ± 0.80 g) for fish fed on diet-3 was significantly higher (p < 0.05) than fish fed diet-1 and diet-2. Specific growth rates (SGR) for diet- 3 were significantly higher (p < 0.05) than diet-1, and marginally more than diet-2 (0.37 ± 0.04 %/ d). Feed conversions were similar (p >0.05), ranging from 1.61 ± 0.26 to 2.07 ± 0.11. Survivals after an 11-week culture were relatively low (< 60%), but generally increased (R2 = 0.667, P = 0.007) with increasing dietary proteins. Diet-3 had a significant higher survival rate (p< 0.05) than diet-1 and diet-2. Significant growth performance was attained with diet-3. This study demonstrated that sinking fish feed pellets can be used to culture wild-caught African fingerlings in captivity.

The fisheries resources of Lake Nakivali: report of a rapid assessment of the Lake Nakivali fishery

Lake Nakivali is one of the four small lakes that form what is known as the Koki lakes system. It is 14 km long, 6 km wide, 26 km2 in area and has maximum depth of 3.5 m at high water level. The lake is located in a lake-swamp complex with River Rwizi as the principle inflow, and a number of peripheral lakes among which are four major ones, i.e. Lakes Nakivali, Mburo, Kachira, and Kijanebalola. The survey therefore established that Lake Nakivali is a healthy ecosystem capable of sustaining fisheries production. While stock enhancement through restocking with fry could boost fish stocks, especially of the Nile tilapia, effective management measures that allow natural regeneration of stocks of indigenous fish species is paramount. This may require closed fishing seasons and control of fishing effort. Tank aquaculture is a viable option for increasing fish production and Ngege (O. niloticus) and Male (C. gariepinus) are candidate fish species for fish farming.

Survey on parasites of Rutilus frisii Kutum in South west of Caspian Sea with the emphasis of pathology of Dactylogyrus frisii and morphological identification of Paradiplozoon sp and Anisakis sp

Rutilus frisii Kutum is one of the most precious fish in the Caspian Sea. Investigation of the various aspects of its biocharactristics. Including its parasite fauna and ecological aspects are of prime importance. In this study the farmed kutum fry were on the focus of investigation in various seasons of the year and prior to their being released in the sea. This included also the study on the kutum spawners caught both from liver and the sea. The results were that 17 external and internal parasite species were distinct within different organs which were further identified down to genus and species. The single celled parasites identified included Ichthyophthirius multifilils, Chilodonella hexastica, Chilodonella pisicola, Trichodina sp Along with the monogene parasites that included Paradiplozoon chazaricum, D. rarissimus, D. turaliensis, D. nybelini, Dactylogyrus frisii. Meanwhile Diplostomum spathaceum constituted the single eyed parasites and the intestinal termatode were Aspidogaster limacoides, Asymphyoldora kubanicum as well as Bothriocephalus gowkongeniss as the sestads. The nematodes defrentiated were Raphidascaris acus, Dioctophyma renale, and Eustrongylides excisus followed by Lernaea cyprinacea as a crustacean. In this study, infestations by single celled parasites, crustaceans and sestod were found to be present only among the farmed kutum fry which varied in terms of percentage and intensity of infection as well as the parasite species and season of the year. The highest percentage of infection among kutum fry and spawners in both fresh water and in the sea during all seasons belonged to monogene parasites (33%). This was up to 100% among spawners. Infection caused by nematodes was exclusively detected among riverine spawners (7.5-5%) and the infection by Asymphyoldora kubanicum and Aspidogaster limacoides among Spawners caught at Sea and rivers varied within different seasons of the year. The infestation of Metacercer diplostomum spathaceum among kutum fry was 12% which compared to spawners was in slightly higher level. The study could identify Dioctophyma renale for the first time in the country and Eustrongylidis excisu was also detected among Rutilus frisii kutum.

Larves et alevins des poissons du Mékong et du Tonlé-Sap (1. Acanthoptériygiens et Ostariophysaires)

The present note deals with a detailed description of larvae and fish fry of species caught in the Mekong River and the Tonlé Sap (Great Lake), one of the world’s most varied and productive ecosystems. In this first part, Acanthopterygii and Ostariophysi have been studied.