Spatial and temporal patterns in the demersal fish community on the shelf and upper slope regions of the Gulf of Alaska

We analyzed data from National Marine Fisheries Service bottom trawl surveys carried out triennially from 1984 to 1996 in the Gulf of Alaska (GOA). The continental shelf and upper slope (0–500 m) of the GOA support a rich demersal fish fauna dominated by arrowtooth flounder (Atheresthes stomias), walleye pollock (Theragra chalcogramma), Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and Pacific Ocean perch (Sebastes alutus). Average catch per unit of effort (CPUE) of all groundfish species combined increased with depth and had a significant peak near the shelf break at 150–200 m. Species richness and diversity had significant peaks at 200–300 m. The western GOA was characterized by higher CPUEs and lower species richness and diversity than the eastern GOA. Highest CPUEs were observed in Shelikof Strait, along the shelf break and upper slope south of Kodiak Island, and on the banks and in the gullies northeast of Kodiak Island. Significant differences in total CPUE among surveys suggest a 40% increase in total groundfish biomass between 1984 and 1996. A multivariate analysis of the CPUE of 72 groundfish taxa revealed strong gradients in species composition with depth and from east to west, and a weak but significant trend in species composition over time. The trend over time was associated with increases in the frequency of occurrence and CPUE of at least eight taxa, including skates (Rajidae), capelin (Mallotus villosus), three flatfish species, and Pacific Ocean perch, and decreases in frequency of occurrence and CPUE of several sculpin (Myoxocephalus spp.) species. Results are discussed in terms of spatial and temporal patterns in productivity and in the context of their ecological and management implications.

The reproductive biology of the porbeage shark (Lamna nasus) in the western North Atlantic Ocean

Reproductive organs from 393 male and 382 female porbeagles (Lamna nasus), caught in the western North Atlantic Ocean, were examined to determine size at maturity and reproductive cycle. Males ranged in size from 86 to 246 cm fork length (FL) and females ranged from 94 to 288 cm FL. Maturity in males was best described by an inflection in the relationship of clasper length to fork length when combined with clasper calcification. Males matured between 162 and 185 cm FL and 50% were mature at 174 cm FL. In females, all reproductive organ measurements related to body length showed a strong inflection around the size of maturity. Females matured between 210 and 230 cm FL and 50% were mature at 218 cm FL. After a protracted fall mating period (September–November), females give birth to an average of 4.0 young in spring (April−June). As in other lamnids, young are nourished through oophagy. Evidence from this study indicated a one-year reproductive cycle and gestation period lasting 8–9 months.

Highly migratory shark fisheries research by the National Shark Research Consortium (NSRC), 2002-2007

The National Shark Research Consortium (NSRC) includes the Center for Shark Research at Mote Marine Laboratory, the Pacific Shark Research Center at Moss Landing Marine Laboratories, the Shark Research Program at the Virginia Institute of Marine Science, and the Florida Program for Shark Research at the University of Florida. The consortium objectives include shark-related research in the Gulf of Mexico and along the Atlantic and Pacific coasts of the U.S., education and scientific cooperation.

Breeding, age and growth of the freshwater shark Wallago attu (Bloch and Schneider) from the Dhir Beel of the Brahmaputra Basin, Assam, India

The Dhir Beel, one of the major live beels of the Brahmaputra Basin, Assam, has an area of 689 ha and situated in Dhubri district of Assam. The dominance of freshwater shark, Wallago attu (8.10%) in the beel is a striking feature. Restricted breeding of W. attu once a year from June to September was observed. The mean observed length was 37.5, 65.0, 84.5 and 99.0 cm in the 6th, 12th, 18th and 24th months of age respectively. The length growth coefficient (K), the asymptotic length (L infinity ), and the arbitrary origin of the growth curve (t omicron ), for W. attu were estimated to be 0.054484 per month, 136.16 cm and 0.0355 month respectively. The calculated life span (T infinity ) of the fish is 123.86 months (about 10 years). The weight growth parameters were estimated where the monthly growth coefficient (K), the asymptotic weight (W infinity) and the arbitrary origin of the growth curve (t omicron) were found to be 0.0743 per month, 7636.92 gram and 0.431908 month respectively. The length-weight relationship follows the cube law.

Studies on shark liver oil and its residue

Seasonal variation in oil and moisture contents and vitamin A potency of oil in livers from different species of sharks landed at Veraval coast were studied. Values of moisture, protein, ash and vitamins in defatted liver residue were determined.

On the results of preliminary fishing trials with shark long lines in Veraval waters

Experimental fishing operations with shark long lines were conducted in the sea off Veraval with a view to studying their efficiency and gathering information on the available resources of sharks to be used for planning the future gear investigations. The trials were undertaken in 1967, employing departmental fishing vessel "Fishtech No. IV" (10.9 m O.L. and 48 H.P. engine). A total of 5525 hooks were employed and 242 sharks weighing 8629 kg were landed. Data on composition of catch, weight of fishes landed, effectiveness of various baits in capture of different species of sharks and effectiveness of gear including its catch efficiency in this area were compiled. Bait preference was also observed in certain species of sharks caught. Chirocentrus dorab proved to be the cheapest and most effective bait in capture of all the three varieties of sharks landed.

Wadge Bank trawl fishery studies. Pt. 1. The effect of the 1928 to 1935 commercial trawling on the demersal stock

The demersal fish stock of Wadge Bank is one of the important fish resources for both Sri Lanka and India. Sivalingam and Medcof (1957) have given an account of its history, general features and relative productivity. According to records the total fishing effort on the bank had been fluctuating and very recently the number of boats operating on the bank has suddenly increased, and there is a possibility that still more will begin operating on the bank in the near future (Mendis, 1965). The increased fishing effort with the possibility of still further increase calls for proper management practices by those concerned, in order to obtain the maximum sustained yield from the demersal stock. For this purpose a detailed study of the past performance of the fishery is essential. With this in view all records of commercial operations up to 1960 are being analysed by the present author and are to be published in a series. This is the first paper in the series and gives a detailed analysis of the first commercial trawling operations from 1928 to 1935. Since there had been a major break of about 10 years between this and the present fishery this data is being analysed separately.

Wadge Bank trawl fishery studies. Pt. 5. Rational exploitation of the resident demersal stock

The general history of the trawl fishery of the Wadge Bank off Cape Comorin, South India (Fig. 1), the nature and composition of its demersal fish population, and the present state of its fishery has been given by various authors (Malpas 1926, Pearson and Malpas 1926, Sivalingam and Medcof 1957, Medcof 1963, Mendis 1965a, 1965b, Sivalingam 1966a, 1966b, 1969a and 1969b). It has been shown earlier (Sivalingam and Medcof 1957, Sivalingam 1969a) that the Wadge Bank stock is made up of two groups. The resident stock which is present on the fishing grounds throughout the year and the migrant stock that appears on the fishing grounds only during the southwest monsoon months. The object of this paper is to discuss the effect of fishing on the resident stock between 1945 and 1962 and based on the information available; assess the maximum sustained yield of the resident stock. The "Bigfish" of the resident stock is the mainstay of the Wadge Bank trawl fishery (Sivalingam 1969a) and it will be shown that this stock has been overexploited from 1953 to 1957. The first sign of recovery was evident in 1960 and continued till 1962. The data since 1962 are not available to the author for analysis. It has been reported by Mendis (1965b) that considerable expansion of the trawler fleet was anticipated in 1966, and if so, the history of the fishery from 1953 to 1957 may be repeated. The assessment presented in this paper should form a rational basis for management programs.

Evaluation of stern trawler operation in the Wadge Bank for economic exploitation of its demersal fish resources

The records of the exploitation of demersal fish resources by trawlers during the past two decades indicated a decline in productivity and uneconomical fishing operations. The possible reasons for the decline can be deduced by analysis of the fishing records of trawlers that have fished in the banks. Such an analysis can also provide a basis for planned management in the exploitation of demersal stocks of fish. This paper attempts to provide such a basis for the Wadge Bank.

A short note on the available information about demersal fish on the shallow part of Sofala Bank

The present information on the biomass and catch of demersal species which constitute a large part of the by-catch of the shrimp trawlers on the Sofala Bank (Mozambique), and thus seem to be more vulnerable than the pelagic stocks to an increase in effort is described. In addition, preliminary data on growth and mortality of two demersal species, Johnius belengerii and Otolithes ruber , which are frequently found in the by-catch, is presented.

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.

Improved chemical methods for extraction of fin rays from shark fins

A survey was undertaken of methods available for the extraction of fin rays from shark fins. The development of new, quicker and easier methods of processing is presented.

Evaluation of quality of shark livers using bio-chemical properties and organoleptic score sheet

Shark livers are considered as an important raw material providing a quality fish oil. It has been reported to aid white — blood-cell production and act as an active ingredient in hemorrhoid treatments. It is also reported that liver oil as a good supplement of vitamin A and poly-unsaturated fatty acids which are important to the development of brain cells in human. Freshness of livers is very important to extract better quality oil. In Sri Lanka, the annual shark production amounts to 8000t, however the quality of livers collected from landing sites has not being measured yet. Present study was conducted to evaluate the quality of silky (Charcarninus fakiformis) shark livers available in Negombo and Beruwala landing sites in the West Coast of Sri Lanka and also to study the relationship between organoleptic and bio-chemical correlation on freshness of shark livers. Liver samples which were collected from landing sites in the West coast of Sri Lanka, were evaluated for external and internal colour, texture and odour. Total volatile nitrogen (TVN), pH value, free fatty acid (FFA%) and peroxide (PV) values of livers were also determined to assess quality. According to the organoleptic scoring system 4.3% of liver samples were categorized as best in quality while 30.4%, 56.5% and 8.7% rated as good, medium and poor in quality respectively at the Negombo and Beruwala landing sites. Bio-chemical analysis showed that the better quality livers had the highest score for sensory evaluation and low values for TVN, FFA and peroxide value while low quality livers gave low score for sensory evaluation and high TVN, FFA, peroxide values. Correlation coefficient of organoleptic scores against total volatile nitrogen value, pH value, free fatty acid % and peroxide value of shark livers were determined by statistical analysis. Organoleptic score of shark livers was found to be highly.