Enhancing potential fish catch in Nigeria's inland waters

The paper enumerated the following ways of improving fisheries:- Effective implementation of the inland fisheries Decree of 1992, stocking and introduction of new species in to small and medium size reservoirs, enhancement of fish catch through increased artisanal fisheries development, fish hatchery development in strategic zones for increased fingerling production to stock reservoirs and natural water bodies, extensive culture development in flood ponds, and encouragement of commercial aquaculture under private entrepreneurship. The paper further elaborate on the strategies for effective implementation of the above guidelines with the hope of offering solution to problems hindering production in Nigeria

The analysis of dieldrin residues in the brain, liver and muscles of the African catfish Clarias gariepinus (Burchell 1822) chronically exposed to dieldrin

Mature adult Clarias gariepinus were obtained at the ABRU hatchery in Sonning (UK), where they had beenbred and reared for several years. These were exposed to two concentrations of dieldrin in water (2.4 mu g super(-1) and 4.0 mu g super(-1). The residue analysis of diedrin in three tissues exposed for on moth at two concentrations was carried out. These were subjected to GLC analytical process. The results indicated significantly (P<0.05) higher residues in liver than in muscle and brain. The results also showed that residue levels were dependant on exposure concentration

Effect of salinity on growth and survival of Clarias gariepinus (Burchell, 1822): Clariidae fry

The effect of different salinity levels on the growth and survival of Clarais gariepinus fry was studied in indoor hatchery system for a period of three weeks. 1000 Clarias gariepinus fry of an average weight 0.37~c0.06g were stocked at 100 fry in five replicated 20 liters plastic bowls. Five salinity levels of 0.2, 0.4, 1.1, 2.1 and 4.2ppt were tested. The results indicated that significant difference P~.0.05 highest weight gain of 0.89~c0.05g was presented by fry in 0.2ppt medium. All fry raised in 4.2ppt died within 24 hours. No significant difference P~,0.05 in weight gain is presented in fry raised in 0.2ppt-2.1ppt. From this study, the weight gain decreases with increase in salinity. Also the survival rate decreases from 0.2ppt to 1.1ppt raised fry while the lowest significant difference P~.0.05 survivals were presented in fry raised in 2.1 and 4.2ppt. Based on these results and foregoing, salinity rate of 0.4ppt is favourable for growth and survival of C.gariepinus fry

Effects of some environmental factors on the fecundity of Tilapia species (Family Cichlidae) in Kigera Reservoir, New Bussa

The effects of some environmental factors on the fecundity of Tilapia species (Family Cichilidae) was carried out at the Kigera dam. Four Tilapia species caught were Tilapia zilli, Hemichromis fasciatus, Sarotherodon galilaeus and Oreochromis niloticus while the environmental factors considered were water temperature, Dissolved Oxygen, pH value, level of rainfall and rate of sunshine and range of time. 43 fish comprising of 25 male with (58.1%) and 18 females having (41.9%) were studied with 74.42% been sexually matured. Both high levels of rainfall and dissolved oxygen favoured fecundity. The spawning peak occurred in (July), environmental factors monitored indicated that dissolved oxygen ranges from 3.7 to 4.45mg/lit rainfall ranges from (34.90mm to 237.80mm) sunshine ranges from (5hrs-8hrs) and pH ranges from (7.35-7.45). The spawning of these species in their natural or hatchery condition is therefore best achieved during the peak of raining season

Restoration of a brown trout (Salmo trutta L.) population to Loch Enoch, an acified Loch in Galloway, South-West Scotland

The authors present the findings of a restoration project in Loch Enoch in Scotland. There are historical references that brown trout was present in Loch Enoch up to the 1920s but it is believed the acidity of loch triggered the disappearance of Salmo trutta. The recent observed reduction in the acidity of L. Enoch to a level close to that found in nearby lochs with trout populations, suggested that trout might now survive in L. Enoch. For a population to survive, all stages in the life-cycle of a species must be able to develop. Accordingly, tests were undertaken, first with eggs and fry. The availability of food was also studied. In October 1994, 3,000 yearling trout of L. Grannoch origin which had been reared in a local hatchery were distributed throughout the loch. The fish population was studied from 1995-98. The authors conclude that survival of the trout population is possible if the acidity of the loch water remains low.

Factors influencing the downstream transport of sediment in the Lough Feeagh catchment, Burrishoole, Co. Mayo, Ireland

Research laboratories in the Burrishoole catchment have been the focus of salmonid research since 1955. One aspect of the research has been to monitor the number of salmon and sea trout migrating to sea as smolts and returning to the catchment as adults. In the early 1990s it became clear that the smolt output from the catchment had declined over the previous two decades. At about the same time the presence of fine particles of peat silt in the hatchery became increasingly apparent and led to a higher incidence of mortality of young fry. These observations and management difficulties led to a study of silt transport in the surface waters of the catchment, which is described in this article. The authors describe geology, soils, climate and hydrology of Burrishoole before examining the sediment deposition in Lough Feeagh.

The blackback flounder and its fishery in New England and New York

A decline in the abundance of blackback flounders, together with the withdrawal of vessels from this fishery, has resulted in a lowered catch in recent years compared to the peak period 1928 through 1931. Data obtained from U. S. Fish and Wildlife Service Hatchery catch records and from fishermen's log book records show a drop in abundance of 63 per cent from the early 1930's to the present in the Boothbay Harbor region and of 31 to 40 per cent in the area south of Cape Cod. Information on the early life history and distribution of young blackback flounders and the size and age composition and distribution of fish subject to the commercial and sport fisheries indicates that the young are the product of local spawning and that the sport and commercial fisheries draw on a resident stock of primarily adult fish.

Experiments with the hatching of salmon spawn 1966-1971. [Translation from: Vann 1972(1) 86-938, 1972]

Experiments were undertaken with the purpose to find out the tolerance of different species of salmon fish in acid hatching water and if different strains of the same species differ in their response. The study was made in the Fins-river hatchery, Marnardal and the assumption tested that the salmon and trout stock from Sorland are adapted to the more acid milieu, and thus more robust in acid water than are comparable fish stocks from areas where the water is only a bit acid or neutral.

Eggs, Larvae and Young of The Striped Bass, Roccus saxatilis

Detailed descriptions of the early development of the striped bass, Roccus saxitilis (Walbaum), with emphasis on variation in size and morphology, sequence of fin formation, changes in body form, and attainment of the full complement of maristic numbers, are presented and illustrated for the first time. The egg is spherical, transparent, non-adhesive and relatively large. It is pelagic and buoyant, although it sinks in quiet fresh water. When unfertilized, it averages 1.3 mm, in diameter, but is 3.4 mm. when fertilized and water-hardened. The granular yolk sac, green when alive and whitish-yellow when preserved, averages 1.2 mm., and the single amber-colored oil globule is about 0.6 mm. in diameter. Newly hatched striped bass prolarvae, which range from 2.9-3.7 mm. in total length, are relatively undeveloped and nearly transparent, with no mouth opening, unpigmented eyes, and a greatly enlarged yolk sac with the large oil globule projecting beyond the head. When 5-6 mm. long the yolk sac and oil globule are assimilated and the postlarvae I show advanced development of the internal anatomy. Although the fish is still transparent, scattered melanophores are found on the head and body and chromatophores in the eyes and the ventro-posterior edge of the body. Postlarvae transform to young between 7 and 10 mm. in length when the finfolds are lost except in the dorsal, anal and caudal regions. The largest fish in this group possess a well-formed skeleton with a full complement of 25 vertebrae. Between 10 and 20 mm. in length all fish are fully transformed, muscular tissue renders most of the internal structure obscure, and the myotomes, which generally correspond in number with the vertebrae, are no longer visible. At fish lengths of 20-30 mm. scales are found on all specimens, and with the exception of the pectoral fin-rays, a full complement of meristic structures is present in all other fins. At this stage the body is pigmented uniformly with small spots. Linear regressions between several dependent variables and the , independent variable of standard length indicate that the rate of development of head, eye. and snout to anus lengths is proportional to the length of the larvae and young. Body depth and standard length are non-linear among newly-hatched larvae. Hatchery-reared striped bass demonstrated a slow rate of growth, and were regarded as "stunted," when compared to growth rates observed in another study and field collections. Observations were also made on abnormal eggs and teratological larvae and young. Blue-sac disease is tentatively identified and described for the first time in larvae and pugnosed larvae and young are also described for the first time in striped bass.

Comparison of observed and predicted dates of eyeing, hatching and swim-up for brown trout and Atlantic salmon

Scholars recently derived simple models from published data for the prediction from water temperature of hatching times for the eggs of brown trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.). A similar model to predict eyeing time for salmon eggs was obtained and used in this study, largely by analogy, to develop equations which might be used to obtain very approximate estimates of eyeing and swim-up times for salmon and brown trout. As the models were based on data for constant temperatures and some of them also had a very inadequate data base, it was desirable that they should be tested, as far as possible, against field and hatchery observations. The present report is a brief summary based on such data as have been obtained to date. None of the data sets were ideal for the purpose and the various inadequacies are discussed later in this report.

Effect of crude oil and some petroleum products on Clarias Gariepinus fingerlings (Catfish: Claridae)

Ninety (90) hatchery bred fingerlings of Clarias gariepinus (mean weight: 0.96 ± 0.1g) were randomly placed in 15 plastic baths (25 litres each) at the Research laboratory and were exposed to different concentrations of oil products to determine their effects on the fish, to facilitate inferential deductions that will enhance effective aquatic environmental management. Three (3) replicate basins of 5 experimental treatments (crude oil, petrol oil, kerosene oil, engine oil and control) were used at a concentration of 1.25ml. L-1. The control experiment was devoid of oil treatment. Six (6) fingerlings were placed in each replicate basin, flooded with 20 litres of clean tap water and fed with nutrafin cichilid food, 2 times daily at 3% body weight. The results showed that the feeding behaviour and swimming performances of fish were reduced after 24 hours of the addition of the various oil pollutants. Mortality of fingerlings in the oiled basins increased as the hours of exposure increased (i.e. 24, 48, 72 and 96 hours). Recovery was not immediate in the treated basin while surviving fingerlings in the control basins grew up to post-fingerlings after 90 days (3 months). There were significant differences (P<0.01 and P<0.05) in the effect of crude oil and the petroleum products on the mortality rate of C. gariepinus when exposed to oil pollutants at 1.25ml. L-1 concentration

Biologie de Ethmalosa Fimbriata (Bowdich) en Côte d'Ivoire. 3 - Étude des Migrations en Lagune Ebrié

Spawning of bonga (Ethmalosa fimbriata Bowdich) takes place in polyhalin waters (Sppt. > 5ppt.). Migrations of young fish were studied by the mean of length data observed in different points of the lagoon from the artisanal fishery. Bonga remain 4 months in the hatchery (6 cm), before they expand in the whole lagoon until the age of 9/10 months. After this expansion phase, the fishes come back to the spawning fields (spawning length: 14/15 cm). Postspawning fishes leave the lagoon. Between birth and spawning, bonga are not affected by salinity changes, but reproduction occurs only in waters where salinity is higher than 5ppt.

Report on the 1995 stock assessment of the Douglas catchment

The River Douglas has a long industrial heritage beginning in the early 18th century with its use by boats carrying goods between Wigan and Tarleton. The River and its tributaries have also historically been, and to a certain extent are still, subject to polluting inputs from the urban, agricultural and industrialised areas located within its catchment. During the early stages in the production of the River Douglas Catchment Management Plan, it became apparent that very little data existed on the populations of coarse and salmonid fish species within the River Douglas system. The data that did exist was largely anecdotal, consisting of catch reports from anglers or water bailiffs, or of dead and distressed fish following pollution incidents. This study was initiated to assess the status of coarse and salmonid fish species within the River Douglas system and so address the lack of knowledge. Eighty two sites were surveyed by electric fishing, including 14 sites using an electric fishing punt and up to four anodes. The data was analysed according to a new National Fisheries Classification Scheme. This classified the sites by the fish stock s present and compared the results with a database containing information from sites around the country that have similar habitat types. A stocking experiment was also undertaken in the River Lostock using chub reared at the Leyland Hatchery. These were marked with an identifiable blue spot in the spring of 1995 and then released into three, previously surveyed, locations in the river. These sites were then resurveyed during the summer stock assessment. This report also Site Reports with details on monitored sites, habitat features and fishery classification.

Report on the 1994 juvenile salmon stocking study of Foxhouses and Grizedale Becks, River Wyre

The aim of this study was to assess the suitability of Foxhouses and Grizedale Becks as nursery habitat for juvenile salmon. A comprehensive fish stock assessment survey of the Wyre catchment was carried out by the NRA in 1992. This survey found that juvenile salmon were absent from two sites studied in Foxhouses Beck. In one site in Grizedale Beck, 0+ salmon were found at very low densities. Juvenile trout were found in all three sites studied in 1992. On the basis of the results of the 1992 survey, these two becks were stocked in 1994 with 0+ salmon reared from Lune broodstock at the NRA's Witcherwell Hatchery. These salmon were stocked at a known density, following a pre-stocking survey. This report examines and compares the results of the pre-stocking survey consisting of fourteen sites in the two becks, carried out between 12/04/94 and 27/04/94 and a post- stocking survey of six sites, carried out between 12/10/94 and 19/10/94. Flow, habitat and in-river obstructions have been shown to affect juvenile salmonid densities. A habitat description is provided for each site surveyed during the course of this study.

Summary document of the work being done in 1992-1993 regarding the migratory salmonid fisheries of the River Ribble catchment

This document lists the work on salmonid fisheries in the River Ribble catchment in the north west of England which was done in 1992-93. The document includes the following: analysis of historical catch data from the River Ribble covering 1937-1991; Ribble and Hodder stock assessment surveys 1992-93 including Swanside Beck; Ribble catch data from game angling log books 1993; results of salmon scale sampling 1993; results of microtagging programme in Hodder and Ribble 1993; Waddow Weir dish counter data 1993; Winkley Hall (Hodder), Locks Weir and Waddow Hall (Ribble) fish counter data 1993; number of fish and ova from Witcherwell Hatchery 1993.