Salvaging the freshwater ecosystems in Nigeria: great threat to sustainable fisheries and aquaculture development

Nigeria, the country of many rivers is also rich in lakes, and wetlands, sustainable and wise use of these inland aquatic ecosystem and water resources has become a matter of widespread and intense concern. Unhealthy freshwater ecosystems and seriously diminishing and unequal availability of quality freshwater call for high quality limnological research and expertise to underpin the enhancement of sustainable fisheries and aquaculture development.In every regard of national health, agriculture and economics, the continued over exploitation and misuse of finite freshwater resources is directly causal to the progressively deteriorating fish production and general standard of living.The integration of basic understanding of inland ecosystems with applied problems and their solutions should be of fundamental concern to all stakeholders in our freshwater resource. This is a basic element in creating an attractive and security ensured economic for investment in fisheries development, including aquaculture. This is the focus of this paper

Resource utilization practices and sustainable development at the Lake Chad basin

The paper examines the resource utilization practices of the Lake Chad in view of the need for sustainable development of the natural resources of the area, which are being recklessly exploited. The issues of obnoxious fishing practices, inappropriate agricultural practices, indiscriminate grazing, reckless fuel-wood harvesting, water pollution etc were discussed. There are clear indications that the current resources utilization practices are pushing the natural resources of the area beyond the limit of their regenerative capacity. This is traceable to institutional weakness and inadequate management strategies at the Lake Chad basin. Suggestions were made towards witnessing a change of attitude to resource use, exploitation and management strategies

Long Run Demand for Energy Services: the Role of Economic and Technological Development

36 p.

Environmental oestrogens and sexual development in fish

This brief paper discusses the assumption that watercourses might be harbouring a chemical(s) affecting the sexual development in fish. Male fish was found with the oestrogen-dependent blood protein, vitellogenin, usually found only in maturing females. The author examines a number of man-made chemicals present in the environment have been found to be oestrogenic. The paper concludes that rivers contain environmental oestrogens that are capable of causing disruptions in the sexual development of fish. Whether or not these environmental oestrogens are causing a widespread disruption in reproduction in wild fish, however, has yet to be determined.

Mitochondria and the development of sea urchin embryos

After artificial activation or fertilization of non-nucleate fragments or eggs of the sea urchin, the mitochondria actively synthesize RNA. The RNA made in non-nucleate fragments is shown to be mostly single stranded and to be associated primarily with the low speed pellet of centrifuged cellular homogenates.

Protein synthesis is observed in non-nucleate fragments in the presence or absence of the mitochondrial RNA synthesis: it is found to be qualitatively similar but quantitatively less in the absence of the RNA synthesis. The continued syntheses of proteins in the non-nucleate fragments in the absence of mitochondrial RNA synthesis provides additional evidence for the presence of a stable messenger RNA component in the unfertilized sea urchin egg.

Since the uptake or actinomycin D was found to be inhibited by the presence of a fertilization membrane, ethidium bromide, at 10 μgs/ml, is used as an effective inhibitor of RNA synthesis in non-nucleate fragments and in early cleavage stage embryos. However, this same concentration of ethidium bromide is found to be only partially effective in blocking RNA synthesis at the mesenchyme blastula stage of development.

Low concentrations of ethidium bromide (2 and 5 μgs/ml) are found not to be lethal but to be capable of producing moderate developmental defects. In the presence of concentrations of ethidium bromide adequate to inhibit all the mitochondrial RNA synthesis (10 μgs/ml of ethidium bromide), from fertilization on, the embryos do not cleave beyond the 4-8 cell stages. When similar concentrations of ethidium bromide are added at an early mesenchyme blastula stage, the embryos do not gastrulate but continue to swim for more than 24 additional hours (adequate for control embryos to develop to a late prism stage). These results lead to the conclusion that mitochondrial RNA synthesis may be very essential for normal development to occur.

DNA is synthesized in the non-nucleate fragments of sea urchin eggs. None of the newly synthesized DNA is found in the closed circular form. When phenol extracted directly from the fragments, the DNA is found to sediment at approximately 38 and 27s in sucrose gradients but neither of these size classes could be found associated with the isolated mitochondria. The template for the synthesis of DNA in non-nucleate fragments remains unknown.

Evaluation of NRA tracking studies. Future projects and technical development

Fish tracking is a valuable technique for the provision of detailed information on the behaviour patterns of individual fish especially during estuarine and riverine migration. 2. Tracking studies help in the provision of a comprehensive description of the variety offish behaviour patterns in response to factors such as water flow, obstructions and water quality. 3. There are advantages to be gained by complementing fish tracking studies with data collected from fish counters and vice versa. 4. An overall evaluation of NRA fish tracking projects is presented in the wider context of NRA strategic research objectives. 5. The requirement for future development of tracking equipment, improved data analysis techniques, better communication and more immediate report preparation is identified. 6. Individual project evaluation is given for NRA (or the appropriate Water Authority predecessor) tracking studies conducted on the Ribble estuary, the River Tamar, River Torridge, Rivers Test and Itchen, River Lodden, the Welsh River Dee, River Glaslyn, River Taff, River Tawe, River Tywi, River Usk, Rivers Avon and Stour and the River Frome. 7. An outline for future strategic research is provided which identifies particular areas for study:- i) Identification of environmental factors which control the entry of fish into rivers. ii) Improvement of the understanding of the relationship between water flow and upstream movement of salmonids. iii) Examination of the detailed movements and behaviour of fish in relation to obstructions. iv) Closer definition of water quality requirements for salmonid fish. v) Definition of habitat preferences of salmonids in rivers. vi) Subsidiary topics such as the movements of non-salmonid fish and the downstream migration of kelts and juvenile salmonids.

Spawning and early development of captive yellowfin tuna (Thunnus albacares)

In this study we describe the courtship and spawning behaviors of captive yellowfin tuna (Thunnus albacares), their spawning periodicity, the influence of physical and biological factors on spawning and hatching, and egg and early-larval development of this species at the Achotines Laboratory, Republic of Panama, during October 1996 through March 2000. Spawning occurred almost daily over extended periods and at water temperatures from 23.3° to 29.7°C. Water temperature appeared to be the main exogenous factor controlling the occurrence and timing of spawning. Courtship and spawning behaviors were ritualized and consistent among three groups of broodstock over 3.5 years. For any date, the time of day of spawning (range: 1330 to 2130 h) was predictable from mean daily water temperature, and 95% of hatching occurred the next day between 1500 and 1900 h. We estimated that females at first spawning averaged 1.6−2.0 years of age. Over short time periods (<1 month), spawning females increased their egg production from 30% to 234% in response to shortterm increases in daily food ration of 9% to 33%. Egg diameter, notochord length (NL) at hatching, NL at first feeding, and dry weights of these stages were estimated. Water temperature was significantly, inversely related to egg size, egg-stage duration, larval size at hatching, and yolksac larval duration.

Sexual differentiation and gonad development in striped mullet (Mugil cephalus L.) from South Carolina estuaries*

This study examined the sexual differentiation and reproductive dynamics of striped mullet (Mugil cephalus L.) in the estuaries of South Carolina. A total of 16,464 specimens were captured during the study and histological examination of sex and maturity was performed on a subsample of 3670 fish. Striped mullet were sexually undifferentiated for the first 12 months, began differentiation at 13 months, and were 90% fully differentiated by 15 to 19 months of age and 225 mm total length (TL). The defining morphological characteristics for differentiating males was the elongation of the protogonial germ tissue in a corradiating pattern towards the center of the lobe, the development of primary and secondary ducts, and the lack of any recognizable ovarian wall structure. The defining female characteristics were the formation of protogonial germ tissue into spherical germ cell nests, separation of a tissue layer from the outer epithelial layer of the lobe-forming ovarian walls, a tissue bud growing from the suspensory tissue that helped form the ovary wall, and the proliferation of oogonia and oocytes. Sexual maturation in male striped mullet first occurred at 1 year and 248 mm TL and 100% maturity occurred at age 2 and 300 mm TL. Female striped mullet first matured at 2 years and 291 mm total length and 100% maturity occurred at 400 mm TL and age 4. Because of the open ocean spawning behavior of striped mullet, all stages of maturity were observed in males and females except for functionally mature females with hydrated oocytes. The spawning season for striped mullet recruiting to South Carolina estuaries lasts from October to April; the majority of spawning activity, however, occurs from November to January. Ovarian atresia was observed to have four distinct phases. This study presents morpholog ical analysis of reproductive ontogeny in relation to size and age in South Carolina striped mullet. Because of the length of the undifferentiated gonad stage in juvenile striped mullet, previous studies have proposed the possibility of protandric hermaphrodism in this species. The results of our study indicate that striped mullet are gonochoristic but capable of exhibiting nonfunctional hermaphroditic characteristics in differentiated mature gonads.

LDLR and PCSK9 Are Associated with the Presence of Antiphospholipid Antibodies and the Development of Thrombosis in aPLA Carriers

Introduction The identification of the genetic risk factors that could discriminate non-thrombotic from thrombotic antiphospholipid antibodies (aPLA) carriers will improve prognosis of these patients. Several human studies have shown the presence of aPLAs associated with atherosclerotic plaque, which is a known risk factor for thrombosis. Hence, in order to determine the implication of atherosclerosis in the risk of developing thrombosis in aPLA positive patients, we performed a genetic association study with 3 candidate genes, APOH, LDLR and PCSK9. Material & Methods For genetic association study we analyzed 190 aPLA carriers -100 with non-thrombotic events and 90 with thrombotic events-and 557 healthy controls. Analyses were performed by chi(2) test and were corrected by false discovery rate. To evaluate the functional implication of the newly established susceptibility loci, we performed expression analyses in 86 aPLA carrier individuals (43 with thrombotic manifestations and 43 without it) and in 45 healthy controls. Results Our results revealed significant associations after correction in SNPs located in LDLR gene with aPLA carriers and thrombotic aPLA carriers, when compared with healthy controls. The most significant association in LDLR gene was found between SNP rs129083082 and aPLA carriers in recessive model (adjusted P-value = 2.55 x 10(-3); OR = 2.18; 95% CI = 1.49-3.21). Furthermore, our work detected significant allelic association after correction between thrombotic aPLA carriers and healthy controls in SNP rs562556 located in PCSK9 gene (adjusted P-value = 1.03 x 10(-2); OR = 1.60; 95% CI = 1.24-2.06). Expression level study showed significantly decreased expression level of LDLR gene in aPLA carriers (P-value < 0.0001; 95% CI 0.16-2.10; SE 0.38-1.27) in comparison to the control group. Discussion Our work has identified LDLR gene as a new susceptibility gene associated with the development of thrombosis in aPLA carriers, describing for the first time the deregulation of LDLR expression in individuals with aPLAs. Besides, thrombotic aPLA carriers also showed significant association with PCSK9 gene, a regulator of LDLR plasma levels. These results highlight the importance of atherosclerotic processes in the development of thrombosis in patients with aPLA.

Variability in spawning frequency and reproductive development of the narrow-barred Spanish mackerel (Scomberomorus commerson) along the west coast of Australia

The narrow-barred Spanish mackerel (Scomberomorus commerson) is widespread throughout the Indo-West Pacific region. This study describes the reproductive biology of S. commerson along the west coast of Australia, where it is targeted for food consumption and sports fishing. Development of testes occurred at a smaller body size than for ovaries, and more than 90% of males were sexually mature by the minimum legal length of 900 mm TL compared to 50% of females. Females dominated overall catches although sex ratios within daily catches vary considerably and females were rarely caught when spaw n ing. Scomberomorus commerson are seasonally abundant in coastal waters and most of the commercial catch is taken prior to the reproductive season. Spawning occurs between about August and November in the Kimberley region and between October and January in the Pilbara region. No spawning activity was recorded in the more southerly West Coast region, and only in the north Kimberley region were large numbers of fish with spawning gonads collected. Catches dropped to a minimum when spawning began in the Pilbara region, when fish became less abundant in inshore waters and inclement weather conditions limited fishing on still productive offshore reefs. Final maturation and ovulation of oocytes took place within a 24-hour period, and females spawned in the afternoon-evening every three days. A third of these spawning females released batches of eggs on consecutive days. Relationships between length, weight, and batch fecundity are presented.

Crab fisheries in Cambodia and the development of crab banks

The crab (swimming crab; Portunus pelagicus) fishery in coastal Cambodia appears to have declined in recent years due to over-fishing and a growth in the number of fishermen, but remains an important source of income for households along the coast. Several initiatives have started since 2007, with support from NGOs, international organizations and the Fisheries Administration (FiA), to test stock enhancement techniques through the release of crab larvae. The so-called “crab bank” initiative involves keeping harvested gravid crabs alive in cages for a few days until they spawn, instead of immediately selling them for consumption or processing. In Cambodia, this initiative has developed within the framework of Community Fisheries (CFis) and thus implies a communitybased approach. The FiA has promoted the continuation of such initiatives; however, the nature of crab fisheries and the results from crab bank initiatives have not been documented in detail. The scope of this study was to understand the diversity of approaches to crab bank development in Cambodia, as well as their operational status and the challenges faced at differen

International legal instruments relevant to fisheries and fishing communities : a handbook. Theme II. Environment and sustainable development

This handbook provides detailed information for a wide range of legal instruments relevant to fisheries and fishworkers. It covers 114 legal instruments, categorized into the following seven themes: Theme I. Human Rights, Food Security, Women and Development. Theme II. Environment and Sustainable Development. Theme III. Oceans and Fisheries Management. Theme IV. Environmental Pollution Theme V. Fishing Vessels and Safety at Sea Theme VI. Labour Theme VII. Trade The handbook also includes the working of the instruments (decision-making bodies, monitoring and implementation agencies, periodicity of meetings, rules for participation in meetings of the decision-making bodies and implementation agencies for States and non-governmental organizations), regional instrument and agencies. Apart from being a ready reckoner to the instruments, it highlights the important sections of relevance to fisheries or small-scale fisheries and fishworkers. The companion CD-ROM provides the full texts of the instruments in a searchable database. The handbook will be useful for fishworker and non-governmental organizations, and also for researchers and others interested in fisheries issues.