Die lage der Fischbestände in Nordostatlantik, Nord- und Ostsee. Einschätzungen des Internationalen Rates für Meeresforschung im Frühjahr 2000

The spring session of ACFM gave advice for a number of stocks in the North Atlantic, North Sea and Baltic. The present assessment of the situation is given here for stocks of higher importance for the German fishery. These are: Blue Whiting: the stock is still relatively high, this, however, will not last very long, due to too intense fishing. Cod in Kattegat: stock is outside safe biological limits. No immediate recovery in sight. Cod in 22–24 (Baltic): stock is inside save biological limits. F, however, is above the recommendation of the IBSFC. Greenland Halibut: state of the stock not quite clear. The present fishing intensity seems to be sustainable. Herring (Atlanto- scandian, Norwegian spring spawner): stock is within safe biological limits, weak recruitment of the recent years will lead to a reduction of biomass. Herring: for Baltic spring spawner in 22–24 and IIIa still no increasing tendency detectable. North Sea Herring: further increasing tendency, with 900 000 t over B lim, good recruitment. Herring in VIa: stable. Redfish: generally decreasing tendency observed, a reduction of the fishery is recommended. Signs of recovery, however, visible for some units

Overfishing, uncertainty, and ocean governance: Lord Perry's question revisited

“Why does overfishing persist in the face of regulation?” The author argues that over fishing,a fundamental cause of the crisis facing our oceans, is the result of the failure of our fishing management agencies (ultimately our politicians and communities) to embrace a small suite of powerful tools (more correctly strategic approaches) which have been developed to account for uncertainty. Broad success in managing fisheries to achieve sustainability goals will only come if these tools are enthusiastically applied. This will not happen until organisational cultures within fishery management agencies undergo a major shift leading to an asset-based biodiversity conservation, rather than resource exploitation, to be placed at the centre of ocean governance.This thesis examines these issues in the context of case studies covering regional, national and provincial (State) fishery management agencies. With the exception of the case study of a regional fishery (the southern ocean krill fishery) all case studies are drawn from Australian experiences. The central recommendation of the thesis is that fishery management agencies, worldwide, should be replaced by biodiversity asset management agencies.

A review of recent advances in commercial tilapia culture

The paper introduces the tilapias as important culture fish; their classification, breeding habits and general ecology are discussed. The versatility and plasticity of their reproduction and growth are major advantages as well as draw backs in their use as culture species. The culture of tilapias in ponds, cages, pens and raceways are described and a comparison of extensive and intensive cultivation is made. The major factors in commercial cultivation of tilapias such as feeds, hatchery/fry production and disease control are discussed. Recommendation is made for the consideration of tilapia as the equivalent of the common carp in tropical African fish culture in either monoculture or in polyculture with other fish species

Utilization of non-piscine pituitary extract in the breeding of Clarias gariepinus

The use of synthetic and non-synthetic hormones have been reported in different regions with the recommendation of different doses. The adaptability of these findings have however not been very successful due to the high cost of building and maintaining hatchery, high cost of synthetic hormone (when available) and high level manpower required. It is obvious that adaptive research in the past ten years in developing countries like Nigeria have been geared towards utilization of resources that are equally effective but cheap and ready to come by. This paper reports the utilization of the pituitary extract of bull frog (Rana adspersa) and the toad (Bufo regularis) in the induced breeding of the African catfish, Clarias gariepinus. The extraction and dosage are discussed alongside the preliminary rearing of fries in outdoor hatchery tanks. Human chorionic gonadotrophin (HCG) and Clarias pituitary extracts were used as control

The resource appraisal survey of clupeids in Kainji Lake, Nigeria

This study includes an analysis of the trawl survey that was carried out by the Kainji Lake Fisheries Promotion Project in May, 1997. The objective of the survey was to assess the biomass and the potential yield of clupeids and the carrying capacity of the beach seine fishery in the entire Kainji Lake (Nigeria). The biomass of the beach seine by-catch was also estimated. The density (kg /km super(3)) of the clupeids was higher in the Bussa and Foge than in the other stations. The lowest density of clupeids was in the Anfani station followed by Jetty, both in the southern basin. These stations were the deepest parts of all the areas trawled, measuring between 37-120 m of depth. There was an inverse correlation between depth trawled and the catch rates of clupeids, though the correlation was poor. The average annual biomass of the clupeids was estimated at 36,769.85 Mt in the entire Lake with an MSY of 11,705.95 Mt. The smaller species, Sierrathrissa leonensis, made up about 97% of the total clupeid population in the lake and occurred at a shallower depth than the larger species Pellonula afzeliusi. From the clupeid production statistics in 1996, it is estimated that the MSY is already overshot by 34%. Therefore, about 698 beach seines instead of the present 810 would be sufficient for sustainable exploitation of the clupeid stocks. Because of the substantial by-catch in the beach seines, this fishing method was banned from Kainji Lake in 1997. An offshore open water seine net is recommended to replace the beach seines on the lake. The number of these nets should not exceed 500. The current ban on beach seine is supported by this study. Nevertheless, and since the ban may not be 100% effective, effort should concentrate on maintaining that the number of beach seines must be kept at most at the present level. Recommendation is made against the introduction of the pair trawling not only from an economic point of view but also for resource conservation, legal and social reasons. The development of this fishery could pose a serious danger to continuity of stocks. It is proposed that priority be given to the development of an open water seine which is at the same level of exploitation as the beach seine and requires similar cost to acquire. (PDF contains 39 pages)

Predictions of fish yields and the status of the Kainji Lake fishery, 1998

Length frequency data was collected for the 6 main species from the Kainji Lake fishery for up to 16 months. Growth parameters were estimated and used for virtual - population and length based cohort analysis. The results from cohort analysis suggest that before the ban on beach seines the maximum economic yield from the fishery was overshot by 70%. Yield per recruit analysis showed that the fish are caught far below their optimum size. Fishing gears and the timing responsible for this early mortality have been identified. After the eradication of seines from the lake a 10% increase in total catch revenue can be expected from the fishery. This is equivalent to an increase in income of Naira 18,300 per annum for each fishing entrepreneur using other methods. A scenario for the regulation of cast net mesh size together with the ban of beach seines has been presented. A further increase of Naira 142 million (N25,500 per entrepreneur) can be anticipated if this is implemented by the Kainji Lake Fisheries Management and Conservation Unit. It is expected that the annual increase in fishing effort presently experienced will cause future yields to decline. The rate of the decline has been reduced by the eradication of the beach seine fishery and will further fall if the minimum mesh size for cast nets is implemented. A recommendation is made to the Kainji Lake Fisheries Management and Conservation Unit to first consolidate the beach seine ban and then to implement a ban of undersized cast nets. (PDF contains 70 pages)

Impact of Nigerian Agricultural Cooperative and Rural Development Bank (NACRDB) loan to artisanal fishermen in Lake Kainji

This study was conducted to assess the impact of Nigerian Agricultural, Co-operative and Rural Development Bank Loan on beneficiaries and non-beneficiaries fishermen in Lake Kainji. A total of fifty fishermen (25 beneficiaries and 25 non-beneficiaries) were randomly selected from five fishing villages along the lake basin. Data collected were scored and the percentages of the parameters were calculated appropriately. The types of loans disbursed to beneficiaries revealed that 52% was cash and 48% was in kind. The credit package ranged between N5, 000 to N150, 000 only. Only 48% of the loans granted were paid while the rest remained unpaid. The results obtained from the membership of fishermen Cooperative showed that 64% of beneficiaries were members while 36% were non-members. Also 36% of non-beneficiaries were members while 64% were not. The Common fishing gears used by the two categories of fishermen include gillnets longline, castnet and driftnets. Sixty percent of beneficiaries and 8% of non-beneficiaries fishermen were using canoe with outboard engines while the rest used canoes with paddles. Beneficiaries earned a higher income (N1, 000 to N9, 000) daily than non-beneficiaries (N1, 000 to N6, 000) daily from sales of fish caught. Major contrainsts to increased catch and income identified include inadequate capital, non- availability of fishing inputs, stealing of fishing gears, lack of access to credit facilities and menace of stump and water hyacinth in the lake. Lastly, recommendation were made for the bank management, government and other lending institutions on how to improve the livelihood of the Artisanal fishermen by increasing the loan usually granted

The role of fishermen cooperative societies in the development of fisheries resources on Kainji Lake basin, Nigeria

Field survey was conducted to evaluate the role of fishermen cooperative in the development of fisheries resources in Kainji Lake. The study was conducted with aid of questionnaires administered in five fishing villages namely Monnai, Yuna, Kaya, Malale and Tunga Danbaba. Ten questionnaires were administered in each fishing village majority of the fishermen interviewed are between the ages of 20-40 years. The results of the educational background revealed that 60% of the respondents were knowledgeable only on Quranic education. Majority of the respondents (86%) was members of fishermen cooperative societies. Only 32% of the respondents indicated to have benefited for loan and credit facilities. Sixty-nine (69) percent of fishermen realized income of between N1, 000-N2, and 000 daily. The major problem facing fishermen cooperative includes lack of capital, lack of access to loan and credit facilities, shortage of adequately trained and well-motivated fisheries extension workers, inadequate fishing inputs and high charge of fishing license fees by Kainji Lake fisheries Management and Conservation Unit (KLFMCU). Recommendation was made on how to improve fishermen cooperative for the development of the lake fisheries resources

Detection of cryptosporidium oocysts in water and environmental concentrates

Whilst current methods for the isolation and enumeration of Cryptosporidium spp. oocysts in water have provided some insight into their occurrence and significance, they are regarded as being inefficient, variable and time-consuming, with much of the interpretation being left to the expertise of the analyst. Two expectations of novel developments are to reduce the variability and subjectivity associated with the isolation and identification of oocysts. Flocculation, immunomagnetisable and flow cytometric techniques, for concentrating oocysts from water samples, should prove more reliable than current methods, whilst the development of more avid and specific monoclonal antibodies in conjunction with the use of nuclear fluorochromes will aid identification. Further insight into the viability, taxonomy, species identification, infectivity and virulence of the parasite should be forthcoming through the use of techniques such as the polymerase chain reaction, in situ hybridisation and non-uniform alternating current electrical fields. Such information is necessary in order to enable microbiologists, epidemiologists, engineers, utility operators and regulators to assess the safety of a water supply, with respect to Cryptosporidium contamination, more effectively.

Linefish resources annual report for the year 2000. Part 1: fisheries assessment

This work reflects the activities of line and trap fishing in Southern Mozambique in 2000. The catch in line fishing has been estimated at 441 mt, according to the DNAP records. The same sources indicated that 1767 days were spent at sea and the estimated catch rate was 250 Kg per boaticlay. Most of the line fishing effort shifted away from Maputo and moved to Inhambane region. The monthly analysis of fishing vessels, stricter controls over catch and effort data submission, development of long-term research programme and the continuation of the on board sampling to improve the data collection are the recommendation for line fishing. The catch of trap vessels increases from 30mt in 1997 to 172 mt in 2000, during which the total number of traps increased from 25 to 300. During this time the number of fishing days has remained relatively constant, as well the soak time. These data sets are thus not compatible with each other, reflecting an increase in daily catch from 243 Kg to 791 kg. The species composition is mainly dominated by P. coeruleopunctatus, C. puniceus, C. nufar and E. andersoni.

Prioritizing seagrass restoration sites: study examines predictors of seagrass bed recovery

Ecologic researchers are modeling the impact of vessel grounding to seagrass beds using GIS in the Florida Keys National Marine Sanctuary. The surface creation tools in the ArcGIS 3D Analyst extension help assess both the damage and recovery of these seagrass beds.

Deriving acceptable biological catch from the overfishing limit: implications for assessment models

The recently revised Magnuson–Stevens Fishery Conservation and Management Act requires that U.S. fishery management councils avoid overfishing by setting annual catch limits (ACLs) not exceeding recommendations of the councils’ scientific advisers. To meet that requirement, the scientific advisers will need to know the overfishing limit (OFL) estimated in each stock assessment, with OFL being the catch available from applying the limit fishing mortality rate to current or projected stock biomass. The advisers then will derive ‘‘acceptable biological catch’’ (ABC) from OFL by reducing OFL to allow for scientific uncertainty, and ABC becomes their recommendation to the council. We suggest methodology based on simple probability theory by which scientific advisers can compute ABC from OFL and the statistical distribution of OFL as estimated by a stock assessment. Our method includes approximations to the distribution of OFL if it is not known from the assessment; however, we find it preferable to have the assessment model estimate the distribution of OFL directly. Probability-based methods such as this one provide well-defined approaches to setting ABC and may be helpful to scientific advisers as they translate the new legal requirement into concrete advice.

Os recursos de algas marinhas de importáncia económica na República popular de Moçambique com especial referéncia para Euchema (Florideae) em Cabo Delgado

Composition, abundance and environmental characteristics of the sea-weed resources of Mozambique were investigated along the whole Mozambican sea shore between May, 1979 and November, 1980. The limits of distribution of tropical algae were identified and located close to parallel 21 degree 00'S. Important concentrations of sea-weeds were found in the southern region, but only the Euchema resource in the coast of Cabo Delgado looked promising for commercial exploitation. Biological studies of Euchema were undertaken, the results of which permit the recommendation of a strategy for immediate harvesting which could yield 400-500 tons annually. Further proposals for the culture of sea-weeds are also included.

Cestodes in fish from a pond at Ile-Ife, Nigeria

The Farm Pond, University of Ife, was impounded by the construction of a dam, below the confluence of two small streams, between March and July, 1967. The pond is located at an altitude of 122.4 m. 0.D., its outline is an indented trapezium occupying 445 dkrn' at maximum fill. Natural food is fed into the pond by its two inlets, and the pond is often coloured a darkish brown due to the abundance of plankton. In 1969, on the recommendation by the Fishery Division, Ministry of Agriculture and Natural Resources, Ibadan, about four standard head-pans of poultry droppings per 40 dkm2 per month were spread uniformly over the pond during 1969 and 1970. Also four pounds of triple superphosphate per acre per month were spread for a period of six months. The pond was drained a number of times in 1970. However, the lowest average level of 1.37 m was recorded in April, 1970, before drainage began; and the maximum depth of 5.7 m was recorded in September and October, 1970.