Showing papers on "Fishing published in 1984"

Why Do Fish Populations Vary

Abstract: Fish populations vary because of density-dependent and -independent processes that determine recruitment, growth, and natural mortality, and in response to fishing. Most of the natural (non-fishing) variability is associated with recruitment, presumably the density-independent effect of fluctuating environmental factors.

Biological observations on sharks caught by sport fishermen off New South Wales

Abstract: Between 1979 and 1982, 523 sharks representing four families and 13 species were examined from sport fishing catches off New South Wales. Additional catch data were available from records of the Sydney Game Fishing Club extending from 1953 to 1979. The species composition of sharks caught changes through the year, probably as a result of seasonal variations in water temperature. Prionace glauca and Isurus oxyrinchus are most abundant in the catches during the cooler months from May to November. Galeocerdo cuvieri, Carcharhinus brevipinna, C. longimanus, C. falciformis, C. limbatus and Sphyrna lewini are taken principally during the warmer months from December to April. The sex ratio of P. glauca and Sphyrna zygaena changes through the year due to a seasonal influx of gravid females. At least six of the species examined give birth off New South Wales and, apart from C. falciformis, all of these appear to have restricted breeding seasons. P. glauca and S. zygaena feed mainly on cephalopods and to a lesser extent on fish, I. oxyrinchus principally on fish, and G. cuvieri mostly on fish, birds, unidentified mammals and cephalopods.

South African Estuaries and Their Importance to Fishes

Abstract: Environmental conditions typical of South African estuaries are contrasted with those of marine inshore waters The life cycle of estuarine fishes is related to important physical and biological characteristics of estuaries The fish fauna is divided into 6 categories according to the extent of their dependence on estuaries This is followed by discussion of the effects of estuarine degradation on these groups Continuing degradation will result in a decline in South Africa's estuarine fish fauna and consequently in recreational angling, in the yield of high-protein food and in economic activities dependent upon this natural resource

Mesopelagic fish, a large potential resource in the Arabian Sea

Abstract: The mesopelagic fish fauna in the Arabian Sea was studied on cruises with R/V ‘DR. FRIDTJOF MANSEN’ conducted during the period 1975–1983. Abundances were estimated using 38kHz echosounders and electronic integrators. The echorecordings were also used to study behaviour. Samples of the fish were collected using commercial sized pelagic trawls. During daytime the mesopelagic fish were found in a layer between 250–350m depth. In areas with high concentrations of Benthosema pterotum an additional very dense layer was usually bound at depths between 150–200m. During night-time, most of the fish are found in the upper 100m, but usually some remain at deep waters (200–350m). The total abundance of mesopelagic fish in the Northern and Western Arabian Sea is estimated to be about 100.10−1 tonnes. In the Gulf of Oman which was surveyed eight times, the estimated biomass ranged between 6–20.106 tonnes. Using a trawl with an opening of about 750m2 the mean catch rate in the shallowest daytime layer was about 5 tonnes.h−1. The highest catch rate obtained was about 100 tonnes.h−1 The catch rates from the deeper layers were low. The most abundant fish, B. pterotum , has a fast growth rate and reaches a length of 4cm in about 6 months. At this stage they spawn and most fish probably die after spawning.

Introduction to the Practice of Fishery Science

Abstract: Preface. The Challenges to Fishery Scientists. Expansion of Fishery Problems. Work of Fishery Scientists. Professional Careers. The Traditional Sciences: The Aquatic Environment. Food Chain and Resource Organisms. Biology of Aquatic Resource Organisms. Ecological Concepts. Analysis of Exploited Populations. Aquacultural Sciences. Application of the Sciences: The Capture Fisheries. The Culture Fisheries. Food Fishery Products. Regulation of Fishing. Aquatic Environmental Management. Fishery Development. Appendices. Bbliography. Subject Index.

Commerce and Culture: The Maritime Communities of Colonial Massachusetts, 1690-1750

Abstract: From their beginnings as simple fishing camps through their emergence as centers of the fishing industry in the eighteenth century, the communities of Gloucester and Marblehead retained the basic features of local life. In this book we are able to view life in these two maritime towns and see the remarkable continuity of traditional values and beliefs.

Scallop and Queen Fisheries in the British Isles

Abstract: History of the fisheries Methods of capture Handling, processing and marketing Behaviour Behaviour in relation to fishing gear and gear efficiency Breeding Age and growth The state of fisheries and stocks Protective legislation and conservation Cultivation and stocking.

A Management Oriented Model of an Abalone Fishery Whose Substocks are Subject to Pulse Fishing

Abstract: I present a model of the exploitation of a fishery whose substocks are subject to periodic fishing during which most fish over the legal minimum length IR are removed. Managers should find the model useful because the period P between successive fishing visits to each substock is an index to exploitation rate, which is usually more easily measured and controlled than the fishing mortality F. Each management choice of IR and closure period P affects both long-term biomass yield and egg production. Using a portion of the South Australian abalone (Haliotis sp.) fishery as a case study, I conclude that increases in either control variable can be used to increase significantly egg production while causing only a marginal decrease in yield. Longer closures also offer potential economic benefits. Depending on alternative hypotheses regarding the recruitment process, controls presently in use may threaten survival of the stock by reducing fertile egg production to critical levels.

Fish rod transport clamp

Abstract: A clamping device is illustrated for securing the elements of a fishing pole, once the extensions have been taken apart.

The efficiency of a new electrofishing technique in determining fish numbers in a large river in Central Poland

Abstract: A new method of determining fish numbers in a large river, which involved electrofishing from boats downstream to an AC electrical barrier, produced capture efficiencies for different species ranging from 28 to 82% when successive pairs of catches were combined Estimates of population density, biomass and production for the 18 species in a 2538 ha segment of the Pilica River, Poland revealed a decline in total numbers of the fish in species diversity between 1963 and 1980 This is attributed to increased fishing pressure, and to a loss in habitat diversity following the loss of many water mills and associated dams The total production estimate of 085 g m−2 year−1 is low compared with the few published estimates for other large rivers Roach, dace, chub, gudgeon and bream were the most numerous fish and they constituted 75% of the total population estimate, and 68% of the standing crop and annual production

The Uncertain Environment of Fishery Scientists and Managers

Abstract: Traditionally, single-species deterministic models have been used to describe the interaction between fish populations and fish harvesters. Management theory and practice often assume that decisions are made based on exact knowledge of the fishery system (i.e., population size, catch, fishing effort, recruitment, and so on, predicated or measured without error). Unfortunately, traditional approaches of fishery science and management ignore a major aspect of fishery systems—uncertainty. Biological productivity of most fishery resources is primarily dependent on recruitment. Recruitment varies by an order of magnitude or more, with little apparent relationship to spawning stock size except at extremely reduced levels. For practical purposes, production of fish populations is stochastic, not deterministic. Furthermore, growth and natural mortality parameters, which are usually assumed constant when analyzing individual populations, actually vary as a result of population interactions. In addition, the contag...

The Atlantic Sturgeon Fishery in South Carolina

Abstract: The fishery for Atlantic sturgeon, Acipenser oxyrhynchus, in South Carolina has undergone a dramatic decline since the turn of the century. Nevertheless, in 1976, South Carolina accounted for 55% of the total United States landings (Maine-Louisiana) for this species. Fishing is seasonal with most effort expended during March-May. The Winyah Bay system near Georgetown supports the primary fishing activity in the state. Major products are the flesh and roe ( caviar ) with the estimated total value of the caviar now greater than that of the flesh. The current fishing gear consisting of anchored gill nets with 30.5-45.7 cm stretch mesh is selective for the females. Sex ratios during the 1978-1982 fisheries averaged 1:2.8 (male : female) and, on a weight basis, females comprised 83% of the landings. Average size of the males caught in 1978-1982 was 158 cm long (fork length) and weighed 41.2 kg, while that of the females was 188 cm and 71.8 kg. Similarly, average estimated age of the females was 16.0 y...

Fishing line signal

Abstract: A fishing line signalling device for attachment to a fishing rod and receiving the fishing line in a manner that a visual or audible alarm or both will be activated when the fish strikes or takes the bait thereby alerting the person using the fishing rod to the fact that a fish has taken the bait or hook. The fishing line signal is battery operated, provided with a switch to selectively actuate either or both the visual and audible signals and is adaptable to any size fishing rod, used with any type of reel and allows a person to fish with more than one rod at a time and is suitable for trolling, still water fishing, night fishing, ice fishing and fresh or salt water fishing. The signalling device includes a switch arm that frictionally grips the fishing line and is spring biased with an adjustment device varying the sensitivity of the device so that when the fishing line is pulled, it is removed from the signalling device so that the switch arm can move to close an electrical circuit to operate a buzzer or light or both.

Structure of the Angling Experience

Abstract: Questions regarding the importance of circumstances within an angling trip and concerning judgements made about the trip were posed to anglers during roving creel surveys in two southeastern United States river drainages. Attitudinal questions addressed one of three topics: Personal; facilities; angling. Several attitudinal responses differed among anglers according to access type (bank or boat), targeted fish group, age, and drainage fished. A principal-axis factor analysis of each drainage's data resulted in the isolation of a recreation and an angling factor. These factors accounted for 52% and 23% of the pooled standardized variance, respectively. Based on the questions asked and on the factor analyses performed, the on-site angling experience was conceptually divided into two parts recreation and one part angling activity. These proportions, generated from measures of importance, reiterate the structure of the fishing ethic embodied in the writings of Izaak Walton and Charles Cotton. Receive...

Temporal changes in a demersal fish and cephalopod community of an unexploited coastal area in Northern Australia

Abstract: A trawl survey of the south-eastern Gulf of Carpentaria carried out at the beginning of a commercial prawn fishery in the 1960s provided data on the demersal fish of an unexploited tropical fish community. The extent of temporal variation in this community was investigated using abundance data on 359 taxa of fish and cephalopods over 13 months in 1963-1964. Seasonal changes in water temperature and salinity were large, particularly in nearshore waters. Catch rates and species richness in nearshore waters were highest during summer, and in offshore waters during autumn or winter. Shannon diversity was variable, with no clear seasonal component. Temporal changes in community composition resulted in large changes between different seasons in the structure of site groups derived by classification; temporal effects within seasons were also found. The numerically dominant species were the leatherjackets Paramonacanthus spp., the ponyfish Equulites leuciscus, the tripodfish Tripodichthys blochii, and the saury Saurida undosquamis. Squid, the ponyfish Leiognathus sp. nr blochi, the butterfly-bream Nemipterus tolu and the grunter Pomadasys maculatus were seasonally abundant. Although species were restricted in their depth range, discrete communities that maintained their identity in different seasons were apparently absent. The relative abundance of many species varied substantially wirh season and probably also over a longer period. Small changes in local abundance were often associated with movement to deeper water at times of high nearshore water temperature (summer) or of reduced nearshore salinity (autumn). Large seasonal changes occurred in the local abundance of estuarine and semidiadromous species. The community shared many species with the demersal fish community of the Gulf of Thailand. It is suggested that similar structural changes in the fish community of the Gulf of Carpentaria may occur in response to intensive fishing. Further research on the effects of demersal fishing and on the interactions of the demersal fish community with commercially important crustaceans is necessary.

Freshwater fisheries management

Abstract: Part 1 - The Resource . The aquatic environment . Water quality . Basic fish biology . Food and food chains . Monitoring and controlling fish stocks . Fish mortality . Part 2: Management Techniques and Methods . Management of coarse fisheries . Management of salmonid fisheries . Construction of stillwaters . Maintenance of stillwaters . Control of aquatic plants . Habitat improvement in still and running waters . Bankside vegetation . Control of pests and predators . Protection of fish stocks by regulations . Part 3: Exploitation . Angling requirements . Formation and management of angling clubs . Commercial exploitation of coarse fish . Crayfish farming . Other uses of the aquatic environment . Appendices - Administration of freshwater fisheries . Careers . National organisations . Fisheries grants . Legislation . Genetic developments and salmonid fishery management . Conversion factors . Common animal and plant names wih scientific equivalents

Probability Angling: A Recreational Fishery Management Strategy

Abstract: Probability angling is a recreational fishery management strategy that uses catch assessment data to establish criteria for evaluating personal recreational angling success. Angling groups on two reservoirs on each of two river drainages in the southeastern United States were asked to rate their incompleted trip quality and fishing success as either poor, fair, good or excellent. Trip-quality ratings were not correlated with ratings of fishing success. Total weight and total number of fish caught per incompleted trip were correlated best with fishing-success ratings among eight descriptors of each group's catch. Drainage catches (via pooling catches from two reservoirs) were significantly different regarding total number of fish per angling group, yet anglers did not rate their fishing success differently between drainages. Collectively, fishermen adjusted their success expectations (i.e., mean number of fish caught within each success category) according to intended target and river system fishe...

A preliminary investigation of the Marine Ichthyofauna in the Tsitsikamma Coastal National Park

Abstract: Sixty-five species representing 29 families were re- corded in a survey of the marine ichthyofauna of the Tsitsikamma Coastal National Park. Visual assessments of the composition of the fish communities at three inshore reef types indicated differences in the species composition and size of fishes present. Areas which are closed to fishing protect many species important to the South African linefishery whereas a recent seaward extension of the park boundary in 1983 will also include areas inhabited by species important to the demersal trawl fishery.

Collapse of the Lake Whitefish (Coregonus clupeaformis) Fishery in Southern Indian Lake, Manitoba, following Lake Impoundment and River Diversion

Abstract: The lake whitefish (Coregonus clupeaformis) fishery of Southern Indian Lake (SIL) has undergone a general collapse since lake impoundment and Churchill River diversion in 1976. The fishery was substantial from its inception in 1941, with a mean annual whitefish catch of 333 500 kg over the 3 decades prior to lake impoundment. The whitefish catch prior to impoundment was composed almost exclusively (> 99%) of light colored, export (A) quality fish that were only lightly parasitized with the muscle cysts of Triaenophorus crassus. The market quality of the catch was maintained by selective fishing of certain lake basins and avoiding areas of the lake that were known to produce lower quality fish. Catch per unit of effort on traditional fishing grounds declined soon after impoundment to about one-half preflooding levels. Total catches were maintained at or near preimpoundment levels by major increases in total effort until 1982, when the whitefish catch fell to about one third of its preimpoundment mean. Fish...

Fishing apparatus and indicating device

Abstract: A fishing apparatus particularly well suited for ice fishing including a housing mounting a fishing reel which deploys a fishing line. Legs are releasably mounted on the housing to support the housing in an operational attitude. An indicating assembly is mounted on the housing for pivotal movement from a ready position to an indicating position upon movement of the fishing reel to indicate that a fish has struck the fishing line.

Biological and Economic Yields for Eastern Bering Sea Walleye Pollock under Differing Fishing Regimes

Abstract: The commercial fishery for walleye pollock (Theragra chalcogramma) in the eastern Bering Sea is the most productive fishery in the United States fishery conservation zone: the total catch exceeded 1 million t in 1982. Historically, this resource has been exploited by foreign distant water fleets; however, there is growing interest among United States fishermen and processors to enter this fishery. Several management strategies have been proposed to facilitate increased domestic participation in this fishery. A bioeconomic simulation was conducted to evaluate the alternative management strategies. The simulation model was an age-structured population model to which economic functions were added. Four alternative fishing regimes were evaluated in the analysis: the current fishery, a fishery directed toward pollock ≳ 36 cm (small fillet), a fishery directed toward pollock ≳ 46 cm (large fillet), and a fishery directed primarily toward small (20-36 cm) pollock for fish paste (surimi). Each fishing re...