The Fisheries for Mangrove Cockles,Anadaraspp., from Mexico to Peru, With Descriptions of Their Habitats and Biology, the Fishermen’s Lives, and the Effects of Shrimp Farming

This paper provides the first description of the mangrove cockle, Anadara spp., fisheries throughout their Latin American range along the Pacific coast from Mexico to Peru. Two species, A. tuberculosa and A. grandis, are found over the entire range, while A. similis occurs from El Salvador to Peru. Anadara tuberculosa is by far the most abundant, while A. grandis has declined in abundance during recent decades. Anadara tuberculosa and A. similis occur in level mud sediments in mangrove swamps, comprised mostly of Rhizophora mangle, which line the main-lands and islands of lagoons, whereas A. grandis inhabits intertidal mud flats along the edges of the same mangrove swamps. All harvested cockles are sexually mature. Gametogenesis of the three species occurs year round, and juvenile cockles grow rap-idly. Cockle densities at sizes at least 16–42 mm long ranged from 7 to 24/m2 in Mexico. Macrofaunal associates of cockles include crustaceans, gastropods, and finfishes. The mangrove swamps are in nearly pristine condition in every country except Honduras, Ecuador, and Peru, where shrimp farms constructed in the 1980’s and 1990’s have destroyed some mangrove zones. In addition, Hurricane Mitch destroyed some Honduran mangrove swamps in 1998. About 15,000 fishermen, including men, women, and children, harvest the cockles. Ecuador has the largest tabulated number of fishermen, 5,055, while Peru has the fewest, 75. Colombia has a large number, perhaps exceeding that in Ecuador, but a detailed census of them has never been made. The fishermen are poor and live a meager existence; they do not earn sufficient money to purchase adequate food to allow their full health and growth potential. They travel almost daily from their villages to the harvesting areas in wooden canoes and fiberglass boats at low tide when they can walk into the mangrove swamps to harvest cockles for about 4 h. Harvest rates, which vary among countries owing to differences in cockle abundances, range from about 50 cockles/fisherman/day in El Salvador and Honduras to 500–1,000/ fisherman/day in Mexico. The fishermen return to their villages and sell the cockles to dealers, who sell them mainly whole to market outlets within their countries, but there is some exporting to adjacent countries. An important food in most countries, the cockles are eaten in seviche, raw on the half-shell, and cooked with rice. The cockles are under heavy harvesting pressure, except in Mexico, but stocks are not yet being depleted because they are harvested at sizes which have already spawned. Also some spawning stocks lie within dense mangrove stands which the fishermen cannot reach. Consumers fortunately desire the largest cockles, spurning the smallest. Cockles are important to the people, and efforts to reduce the harvests to prevent overfishing would lead to severe economic suffering in the fishing communities. Pro-grams to conserve and improve cockle habitats may be the most judicious actions to take. Preserving the mangrove swamps intact, increasing their sizes where possible, and controlling cockle predators would lead to an increase in cockle abundance and harvests. Fishes that prey on juvenile cockles might be seined along the edges of swamps before the tide rises and they swim into the swamps to feed. Transplanting mangrove seedlings to suitable areas might increase the size of those habitats. The numbers of fishermen may increase in the future, because most adults now have several children. If new fishermen are tempted to harvest small, immature cockles and stocks are not increased, minimum size rules for harvestable cockles could be implemented and enforced to ensure adequate spawning.

Electrophoretic and immunotaxonomic studies of three species of marine gastropods from Portonovo coast with reference to population management

Electrophoretic and serological studies of foot muscle protein of three species of Cerithiacea (Telescopium telescopium, Cerithidea fluviatilis and C. obtusum) were carried out to understand their relationships. Living specimens were collected from mud flats and mangrove swamps off Portonovo. Polyacrylamide electrophoresis of proteins from foot muscle extract of T. telescopium, C. fluviatilis and C. obtusum showed that the former had a different densitometric profile as well as more number of protein bands; but the later two species showed a closer related pattern as well as lesser number of protein bands. At the same time these two species are distinguished from each other in their total number of bands and Rf values. Immunological studies using micro-Ouchterlony double diffusion tests which absorbed antiserum indicated that C. fluviatilis and C. obtusum were more closely related as revealed by an identity reactions than T. telesopium as shown by non-identity reactions. Results are discussed in relation to ecological and morphological adaptations

Brackish-water fishery resources

Ceylon has about 300,000 acres of coastal brackish-water areas of which about 100,000 acres constitute shallow lagoons, tidal flats, mangrove swamps and saline marshes, and the rest deeper lagoons and estuaries. While the former represent a vast potential resource with regard to fish farming, the latter are the sites of important fisheries. W. H. Schuster (1951) estimated the average natural production of Ceylon’s brackish waters to be less than 20 lbs. per acre per annum. Since then estimates have been made by the author for a rich lagoon, the Negombo lagoon, a poorly productive lagoon, the Ratgama lake (Dodanduwa) and studies are in progress of some of the other lagoons. The natural production of the Ratgama lake was estimated in 1959 to be 18.5 lbs. per acre per annum while that of Negombo lagoon was estimated in 1960 to be 65 lbs. per acre per annum. It is reasonable to estimate the average production of Ceylon's brackish-waters to be 25 lbs. per acre per annum. Thus the total production is about 3,350 tons per annum. Considering the fact that the island's present total production is 90,000 tons per annum, the brackish-waters contribute 3.7% of it. Schuster (1951) further states that the natural production in the brackish-waters of other countries is around 80 lbs. per acre per annum. In order to increase our average natural production to this value it would seem necessary to consider the nature, biology and fish resources of the brackish-waters and draw some conclusions with regard to their proper exploitation.

Distribuçāo e biologia das espécies de camarāo de águas pouco profundas

This study investigates the life cycle of the two major commercial species of prawns in Mozambique - Penaeus indicus and Metapenaeus monoceros - and their prime nursery microhabitats in the mangrove swamps.

East African Fisheries Research Organization Annual Report 1953

The Annual report covers research carried out during the reporting period 1953 and contains the following Hydrology , Algology , Swamps, Snails and snail-eating Haplochromis, Tilapia Haplochromis, Mormyrus, Protopterus , Fish Physiology and list of Publications by members of E.A.F.R.O.

National Agricultural Research Organisation. Fisheries Resources Research Institute Annual Report 2002/2003

One of the avenues through which the Government objective of poverty eradication in Uganda can be achieved is Fisheries development and management. Up to 20% of Uganda’s surface area is covered by aquatic systems i.e. lakes, rivers, streams and swamps and to a large extent, all these are interconnected. The large lakes: Victoria, Albert, Kyoga, George and Edward are sites of the more important commercial fisheries, but even the smaller water bodies, rivers (e.g. the Rivers Nile and Kagera) and the surrounding swamps provide sources of livelihood to rural areas. Fish is an important source of high quality food, employment revenue and is currently the second most important export commodity next to coffee generating approximately US $ 80 million annually. Fish exports to regional markets are worth at least US $ 20 million annually. Fish flesh is rich in proteins, which are superior to those of beef and poultry. Fish flesh contains an anticholesterol which assists in reducing heart diseases. Some fishes are of medicinal value e.g. haplochromines (Nkejje) are used to treat measles. Most of the fish in Uganda is got from lakes Victoria, Kyoga, Albert and Albert Nile, Edward and George production systems as well as from the 160 minor lakes and rivers and the associated wetland systems. Capture fisheries based in these systems contribute up to 99% of the fish production in Uganda but aquaculture is also picking up. The fishing industry employs up to one million Ugandans

Results of the Austrian-Ceylonese hydrobiological mission 1970 of the 1st Zoological Institute University of Vienna (Austria) and the Department of Zoology of the University of Ceylon, Vidyalankara Campus, Kelaniya (Sri Lanka). Pt 17. The freshwater gastropods of Ceylon

In the present study the specimens collected by the Austrian-Ceylones hydrobiological mission 1970 are described. The freshwater gastropods in this study were collected from 100 different localities, mostly running waters, but some were also collected from stagnant waters like pools, irrigated paddy fields, swamps and water reservoirs (tanks). Listed from these localities are 31 species (and subspecies) 28 species are Streptoneura (=Prosobranchia), 3 species are Euthyneura-Pulmonata Basommatophora.

Wetlands and riparian zones as buffers and critical habitats for biotic communities in Lake Victoria

Despite their ecological and socio-economic importance, Lake Victoria's adjoining "swamps" and lake interface are among the least investigated parts of the lake. The "swamps" a term commonly equated to "wastelands" and the difficult working environment they present in comparison to open water, are major factors for the low level of attention accorded to shoreline wetlands. Moreover, definitions of wetlands highlighted for example in the Ramsar Convention as "areas of marsh, fern, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh or brackish, or salt, including areas of marine water, the depth of which does not exceed six metres" (Ramsar, 1971) were designed to protect birds (water fowl) of international importance. The Ramsar definition, which also includes oceans, has till recently been of limited use for Lake Victoria, because itdoes not fully recognise wetlands in relation to other public concerns such as water quality, biodiversity and the tisheries that are of higher socioeconomic priority than waterfowl. Prior to 1992, fishery research on Lake Victoria included studies of inshore shallow habitats of the lake without specific reference to distance or the type of vegetation at the shore. Results of these studies also conveniently relied heavily on trawl and gill net data from the 5-10 m depth zones as the defining boundary of shallow inshore habitats. In Lake Victoria, such a depth range can be at least one kilometre from the lake interface and by the 10m depth contour, habitats are in the sub-littoral range. Findings from these studies could thus not be used to make direct inferences on the then assumed importance of Lake Victoria wetlands in general.

The major aquatic systems of the Victoria and Kyoga lake basins

The Victoria and Kyoga lake basins form the major aquatic system of this study (Fig. I). The two lake basins share a common evolutionary history and have similar native fish faunas (Graham 1929, Worthington 1929). The two main lakes have also had similar impacts by introduction of Nile perch Lates niloticus and therefore these two lakes can be considered to be similar for ichiogeographical purposes. These lake basins have many satellite lakes isolated from one another and from the main lakes Victoria and Kyoga by swamps and other barriers. Some of these satellite lakes still possess stocks of endemic fish species which are almost extinct from the main water bodies. It was therefore considered that understanding of these lakes would contribute to the knowledge base required to solve some of the problems experienced in Lake Victoria and Kyoga especially the loss in trophic diversity arising. The study was carried out in these two main water bodies (Kyoga and Victoria) and on other satellite lakes e.g Wamala, Kachera, Mburo, Kayanja and Kayugi in the Victoria lake basin and lakes Nawampasa, Nyaguo, Agu, Gigate, Lemwa and Kawi in the Kyoga lake basin (Figs. 2, 3, 4, 5 & 6).

Fish species diversity in the Victoria and Kyoga lake basins: their conservation and sustainable use

Introduction of exotic fish species especially the Nile perch Lates niloticus, is believed to be responsible for the decline of fish species diversity in lakes Victoria, Kyoga and Nabugabo.About 60% of the haplochromine cichlids are thought to have become extinct from L. Victoria due to predation by the Nile perch. However there are many lakes satelite to the lakes Victoria and Kyoga basins which still have fish fauna similar to that of the main lakes. many of the satellite lakes are separated from the main lakes in, which Nile perch was introduced by extensive swamps that provide a barrier to Nile perch .A survey was carried out in a number of these satelite lakes and an inventory made of existing fish species. Their distribution and relative abundances were also determined. The lakes studied included Nawampasa, Nakuwa,Kawi Lamwa Gigate, Nyaguo, Agu, Nabugabo. Kayanja, Kaytigi, Mburo, Kachera and Wamala.Some habitats within the main lakes Victoria and Kyoga, especially those with rocky outcrops· and macrophyte cover that provide refugia for endangered species from Nile perch,were also surveyed) Various stations along the River Nile were also sampled to quantify the fish species that are still resent. Kyoga minor lakes were found to have the highest number of fish species especially of haplochromine cichlids. Many haplochromine trophic groups that were thought to be extinct from 1. Victoria still occur in these lakes.!Some of the satellite lakes, especially lakes Kayugi, Mburo and Kachera still contain .healili populations of oreochromis. I esculentus that could be used as brood stock in fish farming. Many of these lakes should .I ( I therefore be protected for conservation offish species diversity

The biology, ecology, distribution and conservation of some surviving native non-cichlid fish species of Lakes Victoria, Kyoga and Nabugabo

Prior to introduction of non-native fish species into Lakes Victor i a, Kyoga and Nabugabo, the three lakes suppor ted diverse fish fauna representing 13 families consisting of six cichlid genera and fifteen non-cichlid genera. There were about 50 non-cichlid species and over 300 cichlids consisting of mainly haplochromines (Graham 1929, worthington 1929, Greenwood 1960). Many of the species were commercially and scientifically important and provided a rich variety of protein source to choose from. Following introduction of the Nile perch and several tilapiines species, most of the native species were drastically reduced and some have apparently disappeared. The few remaining species appear to be restricted in distribution due to the presence of the Nile perch. They are mainly confined to refugia such as marginal macrophytes, rocky outcrops and small satellite lakes which are separated from the areas of introduction by swamps

Report on Lake Wamala fisheries catch assessment survey 2012

Lake Wamala is one of the small lakes in Uganda, and lies between latitudes 0o 15; and 0o 25' N 31o 45' to longitude 32o 00' E, longitude and at an altitude of 1000m above sea level. Following ths 1961 heavy rains the lake expanded from about 100 to 118 sq. km and the swamps covered almost 60 sq km (Okaranon 1993). This lake was first stocked with Oreohromis niloticus eduardianus populary known as Oreohromis niloticus then Oreochromis leucostictus and then Tilapia zillii then after that it was officially opened for commercial fishing in 1960. Despite of the commercial fishery there used to be subsistance fishing that was mainly by the use of wires and hooks and targeted the Clarias and Protopterus species. The lake fishery used to be highly profitable after the opening in 1960; though in 1970s the fishers started complaining of the declining state of the fishery. At that time the O. niloticus had gone down to less than 1 kg per net per night by 1975 (Okaranon 1993). Due to it led to scientists undertake fisheries surveys in 1975/78 and later 1988/92 then later on there subsquent survey in 2003. Since that time there has been no work done until March 2012 that both catch assessment and frame surveys undertaken to ensure that management issues are addressed concerning this riparian water body. The main objectives of the survey were:- To assess fish production levels in the commercial fisheries of Lake Wamala (Catch Assessment). To assess the fishing effort and facilities available at the fish landings that supports the fisher folks.

Methodology for valuing wetlands in Uganda

The wetlands in Uganda are undergoing rapid degradation. Swamps provide a habitat for birds, fishes and other animals. They have many ecological functions and, furthermore, supply people with multiple resources, such as reeds, herbs, fish and agricultural products. Although some'uses of wetland are sustainable, others lead to rapid deterioration. The main threat to swamps are human activities. One reason for the progressive destruction of wetlands is that the people may not appreciate the existence of and the treasures represented by wetlands even if they live in arm long distance from them. Another reason is that the two most important user groups of wetlands, farmers and fishermen, although having conflicting interests concerning the wetlands, hardly interact. A study, done as part of the Ecotone Project at the Fisheries Research Institute (FIRI), tries to evaluate in monetary terms how much Uganda loses with progressive destruction of wetlands. The study looks first at which uses of the wetlands are of importance and thereafter it examines, what data is needed and available to calculate the values of those uses.

The role of macrophytes in the economy of the lower Sondu-Miriu river of Lake Victoria

This paper highlights the results of a 12 month's ecological study of macrophytes and their role in the economy of the lower Sondu-Miriu river of Lake Victoria. A total of 34 species of aquatic macrophytes were identified. These were grouped as emergent, floating leaved, free floating and submersed. The major community type identified were dominated by Cladium jamaicanse (Crantz) Kurk., Cyperus paprus (L.) and Cyperus latifolius (Poir). The study observed an over dependence on macrophytes by the local community for the supply of bedding, grazing fields, fuel, roofing and other building materials. The white (heart) of Typha shoot, Nile cabbage (Pistia stratiotes and a legume solanum nigrum traditionally known as "osuga" are used as vegetables by local community. The only source of protein in this arid region is the fish caught in the swamps and birds which inhabit the swamp. The swamp provides the only source of green pasture in the dry season for the animals. An export oriented economy has developed involving mat making and basket weaving with exports reaching as far as Japan. The study proposes a rational and sustainable exploitation of the littoral zone to support the adjacent rural community.

The role of satellite lakes in conservation of fish species diversity in the Lake Kyoga basin

Lakes Victoria and Kyoga had, a diverse fish fauna, which was important as food for local population and valuable in scientific studies. Over the past twenty years, the diversity of fish in these lakes had declined due to over-exploitation, introduction of new fish species including the piscivorous Nile perch and degradation of fish habitat. Studies of satellite lakes in the Victoria and Kyoga lake basins suggested that some of these lakes harboured species which had been lost from the main lakes. In order to better understand the extent, to which these satellite lakes may serve as refugia, a faunal survey was undertaken to determine the distribution and nature of the taxa found. Seven satellite lakes and the eastern end of the main Lake Kyoga adjacent to these minor lakes were surveyed over a two-year period for fish species diversity. A total of 68 fish species were recorded of which 41 were haplochromines. Almost all the native non cichlids which occurred in the main lakes (Victoria and Kyoga) before the Nile perch upsurge recorded. Lakes Nawampasa, Gigati, Kawi, Agu and Nyaguo had the highest fish species and trophic diversity. The trophic diversity of haplochromines (based on Shannon Weaver Index) was highest in Lake Nawampasa (1.28), followed by Gigati (1.25), Kawi (1.18), Agu (0.8), Lemwa (0.81), Nyaguo (0.35) and was lowest in the main Lake Kyoga. Potential threats to these lakes were from collectors of ornamental fish species, especially the haplochromines, the spread of the predatory Nile perch and the water hyacinth, which are already in Lake Kyoga, and the destruction of macrophytes through harvesting of papyrus and reclamation for agriculture. The human population around these lakes harvested the fishes for food but the levels of exploitation were still low because the lakes were adjacent to main Lake Kyoga, the major supply of fish. Ornamental fish dealers were encouraged to start captive breeding of the fish for export to reduce pressure on the lakes and demonstrations for breeding were set up at FIRI in Jinja. Meetings and seminars were held with some of the communities living around the lakes sampled and the importance of fish species found in these lakes and the dangers of destructive practices discussed. Representatives of all taxa of fish caught from the lakes were preserved, catalogued and stored in the FIRI Museum. Results from this survey support the motion that these satellite lakes are important refugia for endemic diversity. Based on survey, we recommend that SaIne of these lakes like Nawampasa, Gigati, Kawi, Agu and Nyaguo could be designated as conservation areas of species threatened in the main lakes. One of the factors that seem to have prevented the spread of Nile perch into Kyoga Minor lakes seems to have been the presence of extensive swamps around these lakes and the low oxygen levels that exist in these habitats. Clearing of swamps and vegetation that separate Kyoga minor lakes from the main lake should be avoided to prevent Nile perch from spreading into these lakes.