Local distribution and abundance of swimming crabs (Callinectes spp. and Arenaeus cribrarius) on a tropical arid beach

Distribution, abundance, and several population features were studied in Ensenada de La Vela (Venezuela) between 1993 and 1998 as a first step in the assessment of local fisheries of swimming crabs. Arenaeus cribrarius was the most abundant species at the marine foreshore. Callinectes danae prevailed at the estuarine location. Callinectes bocourti was the most abundant species at the offshore. Abundances of A. cribrarius and C. danae fluctuated widely and randomly. Ovigerous females were almost absent. Adults of several species were smaller than previously reported. This study suggests that fisheries based on these swimming crabs probably will be restricted to an artisanal level because abundances appear too low to support industrial exploitation.

Ontogenetic shifts in natural diet during benthic stages of American lobster (Homarus americanus), off the Magdalen Islands

The natural diet of 506 American lobsters (Homarus americanus) ranging from instar V (4 mm cephalothorax length, CL) to the adult stage (112 mm CL) was determined by stomach content analysis for a site in the Magdalen Islands, Gulf of St. Lawrence, eastern Canada. Cluster and factor analyses determined four size groupings of lobsters based on their diet: <7.5 mm, 7.5 to <22.5 mm, 22.5 to <62.5 mm, and ≥62.5 mm CL. The ontogenetic shift in diet with increasing size of lobsters was especially apparent for the three dominant food items: the contribution of bivalves and animal tissue (flesh) to volume of stomach contents decreased from the smallest lobsters (28% and 39%, respectively) to the largest lobsters (2% and 11%, respectively), whereas the reverse trend was seen for rock crab Cancer irroratus (7% in smallest lobsters to 53% in largest lobsters). Large lobsters also ate larger rock crabs than did small lobsters.

Textural and compositional variations in beach sands along Karachi coast

The texture of clastic sediments is a fairly reliable index of the erosional history and energy conditions of the depositional environment, while its mineralogy reflects the composition of the source rocks. The beach sands of Clifton, Sandspit, Hawkesbay and Paradise Point were studied to determine their erosional history, depositional environment and their source

Preliminary experiments to evaluate the relative efficiency of different natural baits in line fishing

A series of experimental hand-line fishing operations were conducted off the Madras coast employing five different types of natural fish baits. Based on the total catch of fish per day of fishing under each type of bait used, a comparative study on the catching efficiency of the different natural fish-baits was made. The reaction of the fish to particular bait appears to be the result of a complex process. Live baits have the maximum catching efficiency as seen from the fish landings when live prawns were employed as the bait. The procurement of live baits is a serious problem to the fishermen and as such suitable artificial fish lures can be profitably employed.

On the use of different natural baits for sea-fishing in India

Rod and line, hand-line, trolling line and fish-traps are the different types of fishing gears wherein suitable fish baits are employed with a view to luring the catch. The coastal fishermen of India mostly use different types of natural fish-baits to catch fishes like Perches, Carangids, Sciaenids, Scombroids and Elasmobranchs. The reactions of the fishes caught to the different baits used are quite varied. Successful line fishing operations very much depend on the fish-baits. A detailed record of the variety of fishes caught, types of fishing and different baits used by the coastal fishermen of India has been made.

Fishes of Ceylon: a catalogue, key and bibliography

A knowledge of the specific composition of Ceylon fish fauna is essential to any programme of development of commercial fisheries, or the study of Ceylon's ichthyology and the need for cataloguing it has been keenly felt for many years. The need for cataloguing the whole of Ceylon's flora and fauna was stressed by the Natural Science Section of the Ceylon Association for the Advancement of Science during its 1952 annual sessions and it was then that the writer agreed to help satisfy this need by compiling an up-to-date check list of species of two families of fishes, the Clupeidae and the Carangidae, which are important in the beach seine fishery which he was studying at that time. In the course of this work it was decided to expand the check-list to make it comprehensive of all species of fish that have been recorded from Ceylon to date and to supply keys for their identification. This has involved a screening of the pioneer works of Bennet (1834) and Day (1878-1889) and the many subsequent references to Ceylon fish scattered through various scientific journals and other publications, some of them long out and now almost unobtainable.

Ceylon's beach seine fishery

Setting a net in the water and hauling it up onto the beach manually by its two ends is one of the oldest methods of catching fish and it is still employed in several parts of the world: Ceylon is one of these. Here there are several hundreds of beach seines operated by several thousands of fishermen and they contribute 35-40% of Ceylon's total annual fish catch. This means that beach seining been and still is Ceylon's most important single method of fishing. In recent years the beach seine fishery has encountered difficulties which threaten its existence and the seiners have appealed repeatedly to the Department of Fisheries to undertake remedial action. There have been many and conflicting representations as to what this action should be, and the Department is seeking for a wise course through the confusion. As part of its search it asked its Research Division in April 1953, to undertake a study of the seine fishery to describe it, study the nature of its problems and to present any recommendations that seemed appropriate and consistent with the welfare of the fishing industry as a whole. The following is a report on the preliminary phases of that study.

Evaluation on propagation of common carp (Cyprinus carpio Lin.) with hormonal and natural stimuli

The success of breeding of common carp (Cyprinus carpio) using hormonal inducement and environmental stimuli was evaluated considering different sex ratios, and natural and artificial substrates. A total of 18 females (weighing 250 to 2200g) divided into 6 treatments were investigated. A successful spawning was observed in all the treatment groups, only. 66.66% female responded successfully to LHRH-A combined with dompheridone and 83.33% female in natural stimuli. Females induced with LHRH-A and dompheridone found prompt ovulation than that of natural stimulation. A significant variation (F=7.45, P<0.05) was found among the different treatment groups. The number of eggs released appear to depend on body weight (t=15.72, P<0.05), sex ratio (t=7.96, P<0.05) and percentage of ovulated females (t=5.34, P<0.05). Although environmentally stimulated females released more eggs than injected female (t=5.18, P<0.05) but their survival rate was similar (t=1.77, P<0.05). Comparison between the two approaches under the conditions of AIT hatchery shown that both are suitable for spawning induction in common carp. However, environmental stimulation is advantageous because of the less labor and lower cost required for ovulation.

Species composition and abundance of different Macrobrachium species in a natural habitat of Kalu River near Titvala, Maharashtra State

Juveniles of freshwater prawns caught by the traditional cylindrical bamboo traps operated by the local fishermen in a natural habitat of Kalu River near Titvala were sampled every week during September to December 1991 and 1992, to study the composition and relative abundance of different species and their relationship with hydrobiological parameters. The juvenile catch comprised Macrobrachium rosenbergii, M. idella, M. scabriculum and M. bombayensis. Among these M. rosenbergii was more abundant followed by M. idella. It is also observed that high tide catches are more productive than those of low tides.

Effects of natural gas pipeline condensate and crude oil spills, and comments on remediation, with emphasis on south Louisiana salt marshes: a review

This report reviews some of the natural ecological processes at work within a salt marsh as they relate to a spill of natural gas condensate - a mixture of aliphatic hydrocarbons, n-hexane, benzene, toluene, and xylene. It also reviews the environmental impacts of some of the components of natural gas condensate as well as related compounds (crude oil, higher molecular weight hydrocarbons, polycyclic aromatic hydrocarons - PAHs, linear alkyl-benzenes - LABs, etc.) on salt marsh ecosystems in southern Louisiana and elsewhere in the world. The behavior and persistence of these compounds once they have entered the environment is also considered.

Bacterial quality and depuration of the green mussel Perna viridis from natural beds

Green mussel (Perna viridis) and sea water from their natural beds on the coastal areas of Porto Novo were studied between April and August 1996 for their bacterial quality. Water samples from the beds were also analysed for their physico-chemical parameters. The total bacterial count of mussels from natural beds as well as bed waters ranged 10³ organisms per gram of mussel meat suspension and per milliliter of sea water. The faecal coliforms were found to be within the permissible limits. Pathogenic bacteria such as Salmonella spp., Streptococcus spp. and Staphylococcus spp. were absent. The variations in pH, temperature, salinity and dissolved oxygen of the seawater samples were insignificant. The mussels were subjected to depuration by different methods among which chlorination was found to be most effective.

Status of the beach seine fishery in the Hambantota District during 1995-97

Beach seine fishery is one of the oldest fishing methods practiced in Sri Lanka. In the recent past several modifications were observed in the structure of the net and the material used in the construction of nets. beach seine nets made of nylon material were also reported at 4 operating sites out of 17-beach seine landing centers in the Hambantota District. However, traditional beach seine nets made of coir and kuralon were the common nets used in the area. Fishing season extends from September to April of the following year. However, beach seining at Mawella was carried out throughout the year. The estimated average annual effort for the entire study area was about 4250 operations. The mean annual catch rate at Mawella, Kalametiya and Welipatanwila were estimated as 81.8, 290.7, and 167.3 kg/operation respectively. The mean annual catch rate for the entire study area was estimated as 157.3 kg/operation. The beach seines recorded an estimated annual production of 662mt in the Hambantota district. Stoleophorous sp. has made the major contribution to the beach seine catches and it was about 31.7% of the total beach seine production. Leiognathus sp. Carangids and Trichuras sp. have produced 11.5%, 9.5% and 8.5% respectively while Amblygaster sirm and other Sardinella sp. have produced 5.5% and 4.9% respectively. A sirm was found during the months of November, February, March and July. The size range of A. sirm caught by beach seine during February –March period was in the range of 5-12cm (total length). Contribution by Rastrelliger sp. and Sphyreana sp. were 2.9% and 2.6% by each category. Average income of a beach seine operation at Mawella, Kalametiya and Welipatanwila were Rs. 3330/=, 10250/= and 6222/= per operation respectively.

Hydrographical conditions and benthic assemblages in the Suez Gulf, Egypt

The coastal development and human activities along the Suez Gulf leading to sedimentation, degrade the quality of water, disturbing the natural structure and functions of aquatic communities. The Suez Gulf is a large semi-closed area with a 346 km long coastline on the western beach side. The prevailing physicochemical parameters in shallow intertidal waters were measured seasonally over the year. Benthic faunas in the sampling sites were studied indicating their regional distribution in relation to the impact of different environmental parameters in the intertidal region. The concentration of copper in seawater reached high level at St. IV (4.57 ug/1), which is exposed to sewage and petroleum hydrocarbons. The grain size of the sediment is a determining factor for the organic carbon concentration and the sandy substrate enhances organic matter degradation processes. A large number of oil fields are present along the western coast of the Suez Gulf, therefore, cadmium and organic matter appeared to be high. The values of pH did not vary greatly among the different sampling sites. It was high at EI-Ein, El-Sukhna and Ras-Shukeir due to the disposal of mainly acidic sewage and industrial effluents of the two stations Adabiya and Ras-Gharib respectively. The macrobenthos included 71 species embraced mainly from Mollusca (53.5% Gastropoda and 12.7% Bivalvia) and the other invertebrates included 7 groups namely, Rhizostoma, Polychaeta, Cirripedia, Amphipoda, Isopoda, Decapoda and Echinodermata. The distribution of benthos is affected by the temperature and salinity of seawater. The concentration of organic matter in seawater and in sediments in shallow waters shows high values in the central part of the Gulf of Suez.

Natural diet of penaeid prawns in the coastal waters of Mumbai

Foregut contents of eight commercially important species of penaied prawns namely Penaeus merguiensis, Metapenaeus affinis, M. monoceros, M. brevicornis, Parapenaeopsis stylifera, P. hardwickii, P. sculptilis and Solenocera crassicornis were investigated from inshore, nearshore and offshore fishing grounds of Mumbai. Feeding intensity and index of preponderance (IP) of the dietary items were compared statistically for the species, sexes, fishing areas and maturity condition of females. All the species except M. monoceros and P. sculptilis showed that females were better fed than males. The feeding intensity in the three depth-zones was different for M. affinis, M. brevicornis, M. monoceros, P. hardwickii and S. crassicornis, and uniform for P. merguiensis, P. stylifera and P. sculptilis. Acetes spp., prawn remains, polychaetes, benthic crustaceans, foraminifers and fish remains were the important food items of the prawns. Dietary comparison between the two sexes of the species did not show any difference, but mature females of M. monoceros and P. sculptilis had different diets. Comparison of food items for all the species together showed significant difference between the three areas. Crustacean diet was the favorite in the inshore and nearshore, and polychaetes in the offshore waters. All the species except P. hardwickii showed difference in their dietary composition in the three depth-zones. It is concluded that these coexisting species are primarily carnivorous and exhibit diverse food preferences in different depth-zones by browsing on interstitial organisms, chasing epipelagic prey, raptorial predation, scavenging on dead organisms or adopting different temporal abundance to avoid inter-specific competition for food.