Population structure of chum salmon (Oncorhynchus keta) across the Pacific Rim, determined from microsatellite analysis

The Pacific Rim population structure of chum salmon (Oncorhynchus keta) was examined with a survey of microsatellite variation to describe the distribution of genetic variation and to evaluate whether chum salmon may have originated from two or more glacial refuges following dispersal to newly available habitat after glacial retreat. Variation at 14 microsatellite loci was surveyed for over 53,000 chum salmon sampled from over 380 localities ranging from Korea through Washington State. An index of genetic differentiation, FST, over all populations and loci was 0.033, with individual locus values ranging from 0.009 to 0.104. The most genetically diverse chum salmon were observed from Asia, particularly Japan, whereas chum salmon from the Skeena River and Queen Charlotte Islands in northern British Columbia and those from Washington State displayed the fewest number of alleles compared with chum salmon in other regions. Differentiation in chum salmon allele frequencies among regions and populations within regions was approximately 18 times greater than that of annual variation within populations. A regional structuring of populations was the general pattern observed, with chum salmon spawning in different tributaries within a major river drainage or spawning in smaller rivers in a geographic area generally more similar to each other than to populations in different major river drainages or geographic areas. Population structure of chum salmon on a Pacific Rim basis supports the concept of a minimum of two refuges, northern and southern, during the last glaciation, but four possible refuges fit better the observed distribution of genetic variation. The distribution of microsatellite variation of chum salmon on a Pacific Rim basis likely reflects the origins of salmon radiating from refuges after the last glaciation period.

Community management of Mekong River resources in Laos

The Mekong River is one of Asia's greatest rivers. It is the lifeblood of millions of small-scale farmers and fishers in China, Burma, Thailand, Laos, Cambodia and Vietnam. In the Lao People's Democratic Republic (Lao PDR), the river is particularly important because for the landlocked country, the Mekong is the Sea of Laos. In southern Lao PDR, fisheries for native fish species constitute an extremely important source of subsistence protein and income for local people. It has been estimated that wild-caught fish constitute at least 90% of the protein for lowland Laotians living next to the Mekong. Despite the extreme importance of fish to the diets and economics of communities along the Mekong, the resource, and the people who depend upon it, are in danger.

Biodiversity of estuarine fish faunas in West Africa

In West Africa (between Ivory Coast and Sénégal), estuarine environments vary from lagoons to high discharge rivers to inverse hypersaline estuaries. This results in a high diversity of estuarine fish species, with an important turnover and a core of ubiquitous species. The species richness of a given estuary depends on the combination of hydrological factors (marine or freshwater dominance) and biogeography (continental biogeographic regions). The catch rate is higher in lagoons and inverse estuaries than in normal estuaries, which can be explained by the predominance of small juveniles in the latter. Clupeids are the most abundant fishes all over the region, but different systems have different dominant species. Assessing the functioning of West-African estuaries provides useful comparisons to Asian estuarine systems.

An overview of goby-fry fisheries

A number of diadromous gobies, notably Sicydium spp. and Sicyopterus spp., support fisheries based on return migrations of postlarvae (fry) to rivers. Most species are tropical, although close relatives occur in Japan. The life history of this group has often been incorrectly described as catadromous (spawning in the sea or estuary), whereas anadromous (spawning in rivers) would be more accurate.

Investing in Africa: the WorldFish Center's African strategy in summary

Across much of Africa, freshwater and coastal fisheries provide an important source of food and livelihood for many millions of people. In addition, the aquaculture potential of the continent has only recently begun to be developed. To help sustain these capture fisheries, support the emergence of aquaculture and foster the contribution of both to sustainable livelihoods and improved food security, the WorldFish Center is increasing its investment in Africa. The framework for this investment is provided by a new Strategy for Africa and West Asia 2002-2006 that identifies priorities for the Center’s work in rivers and floodplains, lakes and reservoirs, coastal fisheries, aquaculture, policy research and capacity building. The present article summarizes the issues being addressed by the Center and describes initial research priorities.

Length-weight relationships of fishes from tributaries of the Volta River, Ghana Part 1: Analysis of pooled data sets

The parameters a and b of length-weight relationships of the form W = a L super(b) were estimated for 45 fish species sampled in the Oti, Pru and Black Volta rivers, Ghana. Also, the slope and intercepts of regressional enabling standard to total length conversions were estimated for each of these same species. The estimates of b, which ranged from 2.35 to 3.27 have a mean of 2.98, with a s.e. of 0.036. These results are complemented with a brief discussion of the need for data summaries such as presented in this article.

An annotated checklist of freshwater fishes of Armenia

A list of freshwater fishes inhabiting lakes, reservoirs and rivers of Armenia is presented which include 39 species and subspecies belonging to 5 orders, 9 families and 29 genera. A brief description of the ecology, distribution and present status (introductions, threats, commercial value) of these fishes is given.

Reviving the Macrobrachium rosenbergii (de Man) fishery in Vembanad Lake, India

In Vembanad Lake and its confluent rivers (Kerala, India), the catches of Macrobrachium rosenbergii (de Man) were reported to have dwindled to a mere 39 t in the 1980s from average landings of 300 t during the 1960s. This decline is due to the impact of a number of human interventions affecting the ecosystem and, hence, the stocks of M. rosenbergii. Monitoring of landings in 1994-1995 and 1995-1996 indicates an improvement in catches. This paper discusses the reasons for the decline and revival in stocks and suggestions for their replenishment.

Production of freshwater prawns in the Mekong Delta

Currently there are 2 sources of freshwater prawn Macrobrachium rosenbergii production in Vietnam - natural production from the rivers and canals and aquaculture production from ponds and ricefields. An account is given of the production of this prawn in the Mekong Delta. The prawns are harvested primarily by a common small scale method using shelter traps. The total annual freshwater prawn production in Vietnam during 1985-90 was reported to vary from 5000 to 8000 tons, most of it from natural fisheries; although there are no official statistics on the production of farmed prawns, the amount is believed to be very small. The grow-out system includes intensive monospecies pond culture, and semi-intensive or extensive integrated rice-prawn or vegetable-prawn culture.

Length-weight relationships of fishes from tributaries of the Volta River, Ghana: Part II and Conclusion

Slopes and intercepts of length-weight relationships obtained from 37 populations from the rivers Oti, Pru and Black Volta in Ghana were compared using a one way analysis of covariance with fixed effects. Although no significant differences were obtained from this analysis, an ANOVA comparing the magnitudes of mean condition factors (Wx100/SL3) found 9 out of 37 populations significantly different at the 0.05 level. A two-way nested ANOVA using all populations combined, however, did not yield any significant differences between the three rivers. Thus, pooling the data to obtain the results presented in Part I (see Entsua-Mensah et al. Naga 1995) is justified here.

Prospects for fish culture in char areas of Bangladesh

Fish production is considered in the barren chars or sandy land masses created through siltation along river banks and deltas in Bangladesh. The prospects for fish culture in ponds and cages or pen culture in rivers and canals are examined. The socioeconomic implications of fish culture as a livelihood source for communities living in char areas are also discussed.

River fisheries in Africa: their relationship to flow regimes

River fisheries in Africa are important because of their contribution of animal protein to human diets. Such fisheries are highly dependent on hydrological regimes and show considerable year-to-year variation in response to natural climatic events. River flow regimes are being increasingly altered by withdrawals by man, principally for agriculture. The modification of hydrological regimes is leading to diminishing catches of fish and changes in the number and size of the species caught. Given that the trend to remove water from rivers for agriculture and power generation will continue, better appraisals of the impacts of such withdrawals are urgently needed so the policies for water allocation can be better defined. The development of tools to aid in such decision-making is equally important.

Application of Suction-cup-attached VHF Transmitters to the Study of Beluga, Delphinapterus leucas, Surfacing Behavior in Cook Inlet, Alaska

Suction-cup-attached VHF radio transmittes were deployed on belugas, Delphinapterus leucas, in Cook Inlet, Alaska, in 1994 and 1995 to characterize the whales' surfacing behavior. Data from video recordings were also used to characterize behavior of undisturbed whales and whales actively pursued for tagging. Statistics for dive intervals (time between the midpoints of contiguous surfacings) and surfacing intevals (time at the surface per surfacing) were estimated. Operations took place on the tidal delta of the Susitna and Little Susitna Rivers. During the 2-yr study, eight whales were successfully tagged, five tags remained attached for >60 min, and data from these were used in the analyses. Mean dive interval was 24.1 sec (interwhale SD=6.4 sec, n=5). The mean surfacing interval, as determined from the duration of signals received from the radio transmitters, was 1.8 sec (SD=0.3 sec, n=125) for one of the whales. Videotaped behaviors were categorized as "head-lifts" or "slow-rolls." Belugas were more likely to head-lift than to slow-roll during vessel approaches and tagging attempts when compared to undisturbed whales. In undisturbed groups, surfacing intervals determined from video records were significantly different between head-lifting (average = 1.02 sect, SD=0.38 sed, n=28) and slow-rolling whales (average = 2.45 sec, SD=0.37 sec, n=106). Undisturbed juveniles exhibited shorter slow-roll surfacing intervals (average = 2.25 sec, SD=0.32 sec, n=36) than adults (average = 2.55 sec, SD=0.36 sec, n=70). We did not observe strong reactions by the belugas to the suction-cup tags. This tagging method shows promise for obtaining surfacing data for durations of several days.

First Annual Report for the year ended 31st March, 1966

This is the first Annual report of the Cumberland River Authority on information of its activities and responsibilities on river management in its area between the beginning of April 1965, to the end of March 1966. The report contains 5 main sections on water resources, land drainage, fisheries, pollution, and finally the expenditure and income for the 12 month period. The first area that the report deals with is water resources, which includes periodical surveys, hydrometric schemes, acceptable flows, conservation works and a review of rainfall and river flow. The section on land drainage looks at work on improvement schemes, floods, charges and information on maintenance work carried out on rivers including Wampool, Waver, Marron, Irt, Esk, Eden, Caldew, Petteril, Eamont and Annas. The fisheries section covers 5 districts of the River Eden, Esk, Ellen, Derwent, and South West Cumberland. It includes angling information and a general report for salmon and sea trout, brown trout and freshwater fish. It also looks at fish hatchery, fisheries protection and byelaws including licence numbers issued for the different districts. The fourth section on pollution deals with water quality of the rivers and their tributaries from the same 5 areas mentioned above. It also covers information on sewage and trade effluents. The River Authorities preceded the Environment Agency which came into existence in 1996.

Second Annual Report for the year ended 31st March, 1967

This is the second Annual report of the Cumberland River Authority on information of its activities and responsibilities on river management in its area between the beginning of April 1966, to the end of March 1967. The report contains 5 main sections on water resources, land drainage, fisheries, pollution, and finally the expenditure and income for the 12 month period. The first area that the report deals with is water resources, which includes periodical surveys, hydrometric schemes, acceptable flows, conservation works and a review of rainfall and river flow. The section on land drainage looks at work on improvement schemes, floods, charges and information on maintenance work carried out on rivers including Wampool, Waver, Marron, Ellen, Derwent, Esk, Eden, Caldew, Petteril, Eamont, Gelt and Annas. The fisheries section covers 5 districts of the River Eden, Esk, Ellen, Derwent and South West Cumberland. It includes angling information and a general report for salmon and sea trout, Brown trout and freshwater fish. Fish disease and fish hatchery are also included as well as fisheries protection and byelaws. The fourth section on pollution deals with water quality and the results of samples taken from rivers Eden, Eamont, Caldew, Calder, Derwent, Ehen, Ellen, Wampool and Waver are also given. It also covers information on sewage and trade effluents. The River Authorities preceded the Environment Agency which came into existence in 1996.