An evaluation of the effects of blue crab (Callinectes sapidus) behavior on the efficacy of crab pots as a tool for estimating population abundance

Crab traps have been used extensively in studies on the population dynamics of blue crabs to provide estimates of catch per unit of effort; however, these estimates have been determined without adequate consideration of escape rates. We examined the ability of the blue crab (Callinectes sapidus) to escape crab pots and the possibility that intraspecific crab interactions have an effect on catch rates. Approximately 85% of crabs that entered a pot escaped, and 83% of crabs escaped from the bait chamber (kitchen). Blue crabs exhibited few aggressive behavioral interactions in and around the crab pot and were documented to move freely in and out of the pot. Both the mean number and size of crabs caught were significantly smaller at deeper depths. Results from this study show that current estimates of catch per unit of effort may be biased given the high escape rate of blue crabs documented in this study. The results of this paper provide a mechanistic view of trap efficacy, and reveal crab behavior in and around commercial crab pots.

Factors influencing the timing and frequency of spawning and fecundity of the goldlined seabream (Rhabdosargus sarba) (Sparidae) in the lower reaches of an estuary

We have studied the reproductive biology of the goldlined seabream (Rhabdosargus sarba) in the lower Swan River Estuary in Western Australia, focusing particularly on elucidating the factors influencing the duration, timing, and frequency of spawning and on determining potential annual fecundity. Our results demonstrate that 1) Rhabdosargus sarba has indeterminate fecundity, 2) oocyte hydration commences soon after dusk (ca. 18:30 h) and is complete by ca. 01:30−04:30 h and 3) fish with ovaries containing migratory nucleus oocytes, hydrated oocytes, or postovulatory follicles were caught between July and November. However, in July and August, their prevalence was low, whereas that of fish with ovaries containing substantial numbers of atretic yolk granule oocytes was high. Thus, spawning activity did not start to peak until September (early spring), when salinities were rising markedly from their winter minima. The prevalence of spawning was positively correlated with tidal height and was greatest on days when the tide changed from flood to ebb at ca. 06:00 h, i.e., just after spawning had ceased. Because our estimate of the average daily prevalence of spawning by females during the spawning season (July to November) was 36.5%, individual females were estimated to spawn, on average, at intervals of about 2.7 days and thus about 45 times during that period. Therefore, because female R. sarba with total lengths of 180, 220, and 260 mm were estimated to have batch fecundities of about 4500, 7700, and 12,400 eggs, respectively, they had potential annual fecundities of about 204,300, 346,100 and 557,500 eggs, respectively. Because spawning occurs just prior to strong ebb tides, the eggs of R. sarba are likely to be transported out of the estuary into coastal waters where salinities remain at ca. 35‰. Such downstream transport would account for the fact that, although R. sarba exhibits substantial spawning activity in the lower Swan River Estuary, few of its early juveniles are recruited into the nearshore shallow waters of this estuary.

Seasonal distribution, abundance, and growth of young-of-the-year Atlantic croaker (Micropogonias undulatus) in Delaware Bay and adjacent marshes

We examined the spatial and temporal distribution, abundance, and growth of young-of-the-year (YOY) Atlantic croaker (Micropogonias undulatus) in Delaware Bay, one of the northernmost estuaries in which they consistently occur along the east coast of the United States. Sampling in Delaware Bay and in tidal creeks in salt marshes adjacent to the bay with otter trawls, plankton nets and weirs, between April and November 1996–99, collected approximately 85,000 YOY. Ingress of each year class into the bay and tidal creeks consistently occurred in the fall, and the first few YOY appeared in August. Larvae as small as 2–3 mm TL were collected in September and October 1996. Epibenthic individuals <25 mm TL were present each fall and again during spring of each year, but not in 1996 when low water temperatures in January and February apparently caused widespread mortality, resulting in their absence the following spring and summer. In 1998 and 1999, a second size class of smaller YOY entered the bay and tidal creeks in June. When YOY survived the winter, there was no evidence of growth until after April. Then the YOY grew rapidly through the summer in all habitats (0.8–1.4 mm/d from May through August). In the bay, they were most abundant from June to August over mud sediments in oligohaline waters. They were present in both subtidal and intertidal creeks in the marshes where they were most abundant from April to June in the mesohaline portion of the lower bay. The larger YOY began egressing out of the marshes in late summer, and the entire year class left the tidal creeks at lengths of 100–200 mm TL by October or November when the next year class was ingressing. These patterns of seasonal distribution and abundance in Delaware Bay and the adjacent marshes are similar to those observed in more southern estuaries along the east coast; however, growth is faster—in keeping with that in other northern estuaries.

Assessment and possible development of the fishery resources of Pedro Bank

Pedro Bank is about 1,300 square miles in extent and lies at the mouth of the Palk Strait close to the mainland, enabling smaller boats to exploit it. Trawl surveys indicated the presence of substantial demersal varieties on the Pedro Bank, but the results of the early commercial operations indicate that a 135-foot trawler may not be operated continuously on the bank without diminishing returns. Subsequent to the commercial operations extensive surveys with smaller boats and various types of gear were carried out. Of the various types of gear tried out, results from bottom long lining and hand lining operations were promising. Trials were carried out to compare these two types of gear. Though not extensive, these trials indicated that at the initial stages of exploitation of the Bank, hand lining, which is extensively practiced in Ceylon, may be better but as exploitation progresses; with more experience, it should be possible to overcome some of the present disadvantages of bottom long lining and eventually bottom long lining should produce better results. The recently introduced mechanised craft are exploiting only the fringe of the bank and it should be possible to exploit its stocks fully with slightly bigger boats with a 35-40 mile range.

The present-day fishery of the Uganda waters of Lake Victoria

The Uganda waters of Lake Victoria comprise an area of 28,500 square kilometres with a shore line of 2,380 kilometres extending from the Uganda/Tanzania border in the west to the Uganda/Kenya border in the east. A large part of the Uganda waters of the lake is less than 60 metres deep, waters deeper than 60 metres being on the eastern side of the lake. Thus the Uganda part of the lake is tilted towards the east. A number of rivers drain into the lake from the north and the River Nile flows out of the lake towards the Mediterranean Sea. The Ssese, Kome, Buvuma and Busoga Islands form a very distinctive feature of the lake. These are perhaps the remaining high hills which survived the drowning of the northern valleys during the formation of the lake. In fact, in T. P. O'Brien's book 'The Prehistoric Uganda Protectorate (1939)', Solmon gives a critical summary of the work on the formation of Lake Victoria and shows that the northern part of the lake has numerous drowned valleys, a feature which provides varying habitats for particular species of fish and which may have an effect on the species composition reflected in the catches in different areas along the northern shore of the lake. It is interesting to note that although Lake Victoria as a whole has a number of rivers draining into it, Halbfass (1923) calculated and found that 76 per cent of the water entering the lake is precipitation on the lake surface.

The Kandhkelgaon Story: a bold bid by women in Kandhkelgaon Village, Saintala Block, Bolangir District, to break out of their poverty trap

One third of the people on earth who are described as living in absolute poverty are found today in India. “These people,” says Mr B K Satpathy, “are caught in a poverty trap’.” “Poverty trap?” we ask. “These are creative weavers; their cloth has a distinctive style, but those who supply their thread also take away and sell the cloth, paying just a small labor cost for each saree. If they are skilled and work hard this amounts to only 25-30 rupees (60-70 US cents) per day.” Under this arrangement, weaving does not provide enough to live on, and people are seeking ways to escape their entrapment in poverty. (Pdf contains 6 pages).

Report of the PRA carried out at Ihale Beach, Tanzania, April 11-14, 2000

Ihale is a large landing site lying approximately 65 km. from Mwanza along the main Mwanza-Musoma highway. Ihale Beach was selected as a potential candidate for the 3-beaches study because of its proximity to Mwanza, and hence suitability for frequent monitoring; and because it is served by a road accessible during the rainy seasons. As with the first training Participatory Rural Appraisal (PRA) on Kiumba Beach on Kenya's Rusinga Island, the objectives with this PRA were as follows: (a) To identify and understand Ihale's community-based organizations and institutions which have a role in the lake's fishery. (b) To consider the key issues which arise from this study for the involvement of communities and community-based organizations and/or institutions such as those at Ihale Beach, in the co-management of Lake Victoria's fishery.

Report of the PRA carried out at Lwalalo Beach, Uganda, June 5-14, 2000

This document contains the findings of the second Participatory Rural Appraisal (PRA) carried out under the LVFRP. Its principal objectives were to develop base-line information on a Ugandan beach for the 3-beaches survey of the LVFRP.

Report of the PRA carried out at Obenge Beach, Kenya, June 23-26, 2000

This document contains the findings of the third Participatory Rural Appraisal (PRA) carried out on Obenge Beach in Kenya, from the 23rd to the 26th of June 2000, under the LVFRP. Its principal objectives were to develop base-line information on a Kenyan beach for the 3-beaches survey of the LVFRP.

Report of the PRA carried out at Nkombe Beach, Uganda, September 2-10, 2000

This document contains the findings of the fourth Participatory Rural Appraisal (PRA) carried out under the LVFRP. Its principal objectives were to develop base-line information on a Ugandan beach for the 3-beaches survey of the LVFRP.

Report of the PRA carried out at Mwasonge Beach, Tanzania, October 23rd - November 3rd, 2000

This paper comprises part of the so-called "3-beaches Survey" of the LVFRP. In Tanzania, this study has developed to examine two landing sites (Mwasonge and Ihale), and to chart the progress of the newly established Beach Management Units (BMU) at each beach, comparing one BMU against the other. The over-arching objective of this survey was to develop an understanding of the context in which Mwasonge's fishery exists. The study does so by examining the community's history, culture and beliefs, various other socio-cultural factors, their resources, society and economy, wealth and the community's perceptions of wealth. Importantly, the survey examines the community's institutions and its perceptions of fishing rules and changes within the fishery. All of these facets of community life are examined with the use of participatory Rural Appraisal tools, and the images that the study generated are reproduced herein.

A preliminary report on Chanos fry surveys carried out in the brackish water areas of Mannar, Puttalam and Negombo

This paper records the results of the Chanos fry surveys carried out in Mannar, Puttalam and Negombo lagoon areas since 1967, and gives a summary of the earlier surveys. The maximum amount of Chanos fry was obtained from Mannar area during April and May. All three areas have their main commercial fry season in April and May with a second commercially negligible season in October–November. The quantity of fry collected has been utilized to evaluate the potential fry production figures. Mannar 400,000,000 fry/annum. Puttalam 200,000,000 fry/annum. It would be extremely difficult to estimate the number of eggs laid, the larvae hatched and the fry available each year along the coastal areas of Ceylon. It is necessary to obtain biological, meteorological and oceanographical data so as to provide a basis for the prediction and estimation of fry populations in the coastal waters of Ceylon. The suggested ideal season for commercial catches of Chanos fry is April–May with operations to be carried out simultaneously all along the west coast.

Notes on the decline of the dug-out canoe on Lake Albert

Cadwalladr and Stoneman drew attention to the fact that dug-out canoe construction had ceased around the shores of Lake Albert by 1963. Up to this year, however, dug-out canoes were probably still landing the largest proportion of the commercial fisheries catch on the lake, and its associated waterways. It is only since this time that the catch from dug-outs has declined. and currently the commercial fisheries of the lake are based predominantly on motorised planked canoes.