Growth performance of Nigerian fish stocks

Parameters of the von Bertalanffy growth function are presented for 42 fish stocks belonging to 16 families, 22 genera and 27 species. The growth performance index, Phi '(= log K + 2logL sub( infinity )), was computed for each stock and was found to be highest in male Gymnarchus niloticus (Gymnarchidae) from Lake Chad and lowest in Chrysichthys auratus (Bagridae) from the Cross River. Mean Phi ' for major fish genera and families are also presented and was highest in brackishwater fishes, closely followed by freshwater and inshore marine water fishes.

Palaeoenvironmental analysis based on alluvial ostracod assemblages of the Cenicero section (lower Miocene, NW Ebro Basin)

In this work we perform for the first time a palaeoenvironmental and biostratigraphic analysis of the lower Miocene alluvial deposits of the Cenicero section (NW sector of the Ebro Basin; N Iberian Peninsula), based on the ostracod and micromammal assemblages. One of the main characteristics of this section is the unusual abundance on non-reworked ostracods present in the studied samples compared to other European sequences of similar age and sedimentary environment. This fact has allowed us to develop precise palaeoenvironmental reconstructions. The variations of the identified ostracod assemblages, defined by species such as Cyclocypris laevis, Ilyocypris bradyi, Ilyocypris gibba, Limnocythere sp. or Pseudocandona parallela, record the development of small, ephemeral and shallow ponds in a distal alluvial and/or floodplain environment. Towards the upper part of the section the ponds appear to be less ephemeral, being the aquatic systems more stable for ostracods development. Variations in the water temperature and salinity have been observed along the section, which are related to changes in the local pluviometric regime. On the other hand, the presence of micromammals in one of the studied samples has allowed the precise dating of this section. Thus, the presence of Armantomys daamsi dates the Cenicero section as Agenian (lower Miocene), local zone Y2 (MN2).

The half-lives of biological activity of some pesticides in water

In the absence of analytical methods, the half-lives of biological activity of pesticides can be estimated by bioassays. To determine the half-lives of biological acivity of pesticides to fish, static bioassays were conducted in the laboratory with ten different formulations of pesticides using Labeo rohita as a bio-indicator. The half-lives of biological activity for ten different pesticides in soft water at pH 7.5 and 27°C, ranged from 4.6 days to 11.8 days. The half-life of biological activity of Sumithion 50% EC was only 4.6 days. In contrast, Dimecron 50% EC degraded very slowly and its half-life of biological activity on L. rohita was about 11.8 days. Sumithion 50% EC, Padan 50% SP, EPN 45% EC, Diazinon 40% EC and Diazinon 10 G degraded in less than five to seven days indicating that these pesticides are desirable for rice-fish culture. Contamination by pesticides with long-term residual toxicity in waters may eventually cause high levels of fish mortality.

Nearshore fish resources and fisheries around Kigoma, eastern coast of Lake Tanganyika

The fish habitats along an inshore water stretch along the eastern/central coast of Lake Tanganyika are discussed and a quantitative analysis of the species composition, distribution and abundance of the littoral fishes within the area of study is presented. Seventy-one species of fish belonging to 48 genera and to 15 fish families were collected and identified during the study. The majority of species belonged to the Cichlidae family. Intensive beach seining for clupeids is suggested as one of the causes of low fish biomass in the area surveyed. The areas south of Kigoma appeared to contain more fish, with average catch rates of 11.7 kg/haul than those north of Kigoma where average catch rates of 7.6 kg/haul were recorded. Some suggestions for improved management of these resources are given.

Rice-fish-vegetable integrated farming: towards a sustainable ecosystem

An outline is given of procedures to take in order to adopt an integrated rice-fish-vegetable farming system in India. Vegetables, which are cultivated in the dikes of the system, may include Luffa acutangula, Vigna unguiculata and Phaseolus vulgaris . When the water depth of the field rises to 30-40 cm, fish fingerlings (Puntius javanicus, Cyprinus carpio and Labeo rohita ) and prawn juveniles (Macrobranchium rosenbergii ) may be stocked. The advantages of such a system are listed and include year round employment opportunities for the farm family and improved farm family income and nutrition.

Fish demand and supply projections

It has been predicted that the global demand for fish for human consumption will increase by more than 50% over the next 15 years. The FAO has projected that the increase in supply will originate primarily from marine fisheries, aquaculture and to a lesser extent from inland fisheries, but with a commensurate price increase. However, there are constraints to increased production in both marine and inland fisheries, such as overfishing, overexploitation limited potential increase and environmental degradation due to industrialization. The author sees aquaculture as having the greatest potential for future expansion. Aquaculture practices vary depending on culture, environment, society amd sources of fish. Inputs are generally low-cost, ecologically efficient and the majority of aquaculture ventures are small-scale and family operated. In the future, advances in technology, genetic improvement of cultured species, improvement in nutrition, disease management, reproduction control and environmental management are expected along with opportunities for complimentary activities with agriculture, industrial and wastewater linkages. The main constraints to aquaculture are from reduced access to suitable land and good quality water due to pollution and habitat degradation. Aquaculture itself carries minimal potential for aquatic pollution. State participation in fisheries production has not proven to be the best way to promote the fisheries sector. The role of governments is increasingly seen as creating an environment for economic sectors to make an optimum contribution, through support in areas such as infrastructure, research, training and extension and a legal framework. The author feels that a holistic approach integrating the natural and social sciences is called for when fisheries policy is being examined.

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).

A High-Speed Fish Evisceration System (FES) for Bycatch and Underutilized Fish Stocks

Development of a high-speed and high-yield water-powered fish evisceration system (FES) to efficiently preprocess small fish and bycatch for producing minced fish meat is described. The concept of the system is propelling fish in a stream of water through an arrangement of cutting blades and brushes. Eviscerated fish are separated from the viscera and water stream in a dual screen rotary sieve. The FES processed head off fish, weighing 170–500 g, at the rate of 300 fish/min when used with an automatic heading machine. Yields of mince produced from walleye pollock, Theragra chalcogramma; and Pacific whiting, Merluccius productus; processed by the FES ranged between 43% and 58%. The maximum yield of minced muscle from fish weighing over 250 g was 52%, and the yield of 250 g was 58%. Test results indicated that surimi made from minced meat recovered from fish processed with the FES was comparable in quality to commercial grade surimi from conventional systems. Redesigned for commercial operation in the Faeroe Islands (Denmark), the system effectively processed North Atlantic blue whiting, Micromesistius poutassou, with an average weight of 110 g at a constant rate of 500–600 fish/min, producing deboned mince feeding a surimi processing line at a rate of 2.0 t/h. Yields of mince ranged from 55% to 63% from round fish. Surimi made from the blue whiting mince meat produced by the FES was comparable to surimi commercially produced from blue whiting by Norway and France and sold into European markets.

Considerations about effective dissemination of improved fish strains

Aquaculture production systems in developing countries are largely based on the use of unimproved species and strains. As knowledge and experience are accumulated in relation to the management, feeding and animal health issues of such production systems, the availability of genetically more productive stock becomes imperative in order to more effectively use resources. For instance, there is little point in providing ideal water conditions and optimum feed quality to fish that do not have the potential to grow faster and to be harvested on time, providing a product of the desired quality. Refinements in the production system and improvement of the stock used must progress hand in hand. In this paper we deal separately with genetic and non-genetic issues pertaining to the multiplication and dissemination of improved strains. The separation is somewhat arbitrary, and as will be evident from our discussion, there is frequent interaction between the two.

River Teign Fish Survey 1990

This is the River Teign Fisheries Survey from 1990 by the Environment Agency Archives South West (unpublished). The aim of the survey was to assess the distribution and relative abundance of salmonid fish in the River Teign. Thirty six sites were examined; twenty one of them had been examined in previous quantitative fish surveys. At each site, all fish species encountered were caught and measured, however, only data for salmonid fishes has been examined. The results are compared with those of the 1963 and 1972 surveys carried out by the Devon River Authority and the 1975 and 1979 surveys carried out by South West Water Authority. A full list of sites together with their location, fish densities, lengths, weights and ages is attached.

Gunnislake Fish Counter Annual Report 2002

This is the Gunnislake Fish Counter Annual Report 2002 from the Environment Agency South West Region, which was held on March 2002. It presents the daily upstream counts of migratory salmonids recorded on the River Tamar at Gunnislake Weir fish counting station in 2002. The data within this report covers the period of the commercial migratory salmonid net buy-back scheme and the National Spring Salmon Bylaws. The report contains section on Net Buy-Back; Species Apportionment; Validation of counter efficiency; results as total number of migratory salmonid (salmon and Sea Trout) counted moving upstream in 2002 at Gunnislake; video validation and Counter Efficiency; and Discussion. The section Discussion includes Salmon and Sea Trout counts recorded on the River Tamar 1995-2002, other fish species observed as sea lamprey and Environmental Factors (river flows, water temperature, and barometric pressure).

Effects of water quality in Bassenthwaite Lake on anglers' catches of salmon and sea-trout in the River Derwent

This is the report on the Effects of Water Quality in the Bassenthwaite Lake on Anglers Catches of Salmon and Sea-trout in the River Derwent April 1993 by the Institute of Freshwater Ecology. An analysis of the catch statistics for salmon and sea-trout in the Rivers Derwent and Cocker was undertaken in relation to available information on the algal water quality in Bassenthwaite Lake to test the hypothesis that poor catch returns were associated with a deterioration of water quality within the lake. Analysis of the catch statistics failed to reveal any correlation between water quality and catch returns for either species of fish and it is concluded that any water deterioration in Bassenthwaite Lake has not caused any major damage to the salmon and sea trout fisheries of the Derwent/Cocker system. This conclusion is supported by the analysis of the Windermere/Leven and Crake system, where no correlation could be found between lake water quality and downstream catches of migratory salmonid fish. However, the possibility still exists and such an effect might be detected by further field work on the macroinvertebrates and on the composition of potential salmonid spawning in the area.

The effect of abstraction on fish and fisheries

This is the report on the Effect of Abstraction on Fish and Fisheries presented at the 24th IFM Annual Study Course, The Changing Face of Fisheries September 1993 at Cardiff. Water is abstracted from rivers for a wide variety of uses and causing potential for conflicts between abstracters, fisheries and conservation interests, especially during natural low flows. It looks at the potential effects that flow reduction has over various stages of salmonids at various stages of their life history. The flow at the time of smolt migration has been found to be positively correlated with the number of returning adults, and flow is considered to be one of the most important environmental factors inducing salmonids to enter fresh water and ascend rivers. The importance of time series data on fish stocks and angling success together with models which ultimately relate discharge to standing stock are discussed in relation to the setting up of Minimum Acceptable Flows.

A comparative survey of the fish populations of 10 West-Midlands meres of SSSI status

This is a comparative survey of the Fish Populations of 10 West-Midlands Mere of Site of Special Scientific Interest Status. The meres of the Shropshire-Cheshire plain (West Midlands) comprise over 60 water bodies. Water quality in the meres ranges from naturally eutrophic to nutrient limited and some of them have received Site of Special Scientific Interest status (SSSIs). This survey was commissioned in order to obtain quantitative information on the fish fauna of selected SSSIs and evaluate the likely impact of fish on other species within the community. The current survey was concerned with 10 of the West Midlands’ meres, a cross section of sites was selected. Sites were widely distributed from Marton Pool in the south-western part of Shropshire to Tabley moat in Chesire. Meres varied in size, depth and nutrient status. All were to be sampled using the methods outlined. The report is divided into different sections for clarity and ease of reference. The materials and methods section provides an outline of the location and status of each mere and information on known fish species present. The results were considered individually and comparatively, relative abundance of fish, species present, their diet, sex, age, parasite burdens and growth. Inter-site comparisons were made using information derived from echo-soundings, growth rate, diet, and species abundance for each site. The final section will be in the form of a general discussion, comparative information from longer term studies, conclusions and recommendations.

Water quality monitoring in the Mersey

This is the Water Quality Monitoring in the Mersey Estuary report produced by the Environment Agency in 2001. This report focuses on the Water Quality Monitoring Programme held in the Mersey Estuary. Since the mid-1960s water samples have been collected at approximately monthly intervals along the length of the estuary between Warrington and New Brighton and in later years further off-shore. This data-set provides an invaluable resource to determine how the very large capital spending of recent years has resulted in the dramatic improvements in water quality that we are now able to record. Initially, the interest was focused on parameters such as dissolved oxygen, BOD, nutrients and suspended solids. Over the last decades, as analytical methods have improved, toxic metals and persistent organic compounds have been included in the routine monitoring programme at a limited number of sites. Moreover, with the introduction of the European Water Framework Directive monitoring programmes it was an opportune time to review the Mersey monitoring strategy. This revised monitoring programme required data from several other components (water, sediments, flora, fauna, fish and birds. This report also contains information about Routine monthly surveys, Special surveys, Chloralkali Directive, UKNMP, British Geological Survey, EDMAR and NERC Environmental Diagnostics Thematic Programme.