A new deep-sea crab, genus Chaceon, from the Arabian Sea (Crustacea, Decapoda, Geryonidae)

The sixth nominal species of Chaceon to be recorded from the western Indian Ocean is named from a specimen collected off Somalia in 504-506 meters. Chaceon somaliensis, n. sp., resembles C. macphersoni (Manning and Holthuis, 1988) and differs from the other four species known from the area in having the dactylus of the walking legs dorsoventrally depressed. It differs from C. macphersoni in having slenderer legs, a smoother body, and a much deeper, evenly curved orbit.

Learning the Structure of Deep Sparse Graphical Models

Deep belief networks are a powerful way to model complex probability distributions. However, learning the structure of a belief network, particularly one with hidden units, is difficult. The Indian buffet process has been used as a nonparametric Bayesian prior on the directed structure of a belief network with a single infinitely wide hidden layer. In this paper, we introduce the cascading Indian buffet process (CIBP), which provides a nonparametric prior on the structure of a layered, directed belief network that is unbounded in both depth and width, yet allows tractable inference. We use the CIBP prior with the nonlinear Gaussian belief network so each unit can additionally vary its behavior between discrete and continuous representations. We provide Markov chain Monte Carlo algorithms for inference in these belief networks and explore the structures learned on several image data sets.

The deep crab - Geryon quinquedens: first notes on its biology off Mozambique

The deep crab Geryon quinquedens was the objective of an exploratory fishing operation with long lines of baited traps along the slope of southern Mozambique and was caught between 250 and 850 m. Data were analysed from the start of the operation in May, 1979 until March, 1980. The availability of the resource is discussed on the basis of catch rates. Size composition of the catches shows the bigger size of the males and suggests a stratification of the resource by area. Females dominate in shallower waters whereas the interval at which the sex-ratio equals one is identified at 400-450 m. Reproduction is discussed in connection with recruitment and an hypothesis is advanced for an exponential growth rate of about 10 mm per month.

Stock assessment of the deep-water spiny lobster Palinurus delagoae, off Mozambique

Preliminary estimates of growth parameters and mortality are presented for the deep-water spiny lobster Palinurus delagoae fished off Mozambique. The length-converted catch curve shows three levels of total mortality (year-1): Z=2.9 for the smaller sizes; Z=1.4 for intermediate, and Z=0.6 for the larger lobsters. These results are confirmed by a length-structured virtual population analysis. Yield-per-recruit analysis suggests that a long-term yield, at least 50% higher than the present one, could be obtained by increasing the mean size at first capture from about 6 cm (carapace length) to about 10 cm.

Development of off-shore and deep-sea fishing in Sri Lanka

Since 1950 onwards, a practice has grown in Sri Lanka of dividing the marine fisheries into three different classes depending on the location of the resource to be exploited viz. coastal fishing, off-shore fishing and deep-sea fishing. The author describes commercial fishing activities, paying attention to changes emerged and future prospectives.

Problems facing the deep-sea fishing industry in Sri Lanka

Fishing in Sri Lanka has been carried on largely with the use of traditional methods and in recent years there has been a marked increase in the use of mechanized craft for fishing. Although some effort has been made in the sphere of deep-sea fishing both by trawlers and long line tuna boats, such efforts have not made a significant contribution towards improving the industry. The progress of deep-sea fishing in Sri Lanka has been hindered due to a number of reasons described by the author.

Demersal fishery resources of Sri Lanka and its present level of exploitation with special reference to off-shore and deep-sea waters

Following a brief review of development of demersal fishing off Sri Lanka, the author reviews the fishing grounds of the Wadge Bank, the Pedro Bank, and the Mannar Bank. He reviews the deepwater trawling fisheries particularly in relation to the 1972 survey conducted by the 'Optimist' and also small boat trawling in coastal waters. Lastly he considers handlining for groundfish, which is principally conducted by fishermen operating traditional craft.