Showing papers on "Fishing published in 1990"

Effectiveness of Crab and Lobster Traps

Abstract: Traps are a versatile and powerful fishing gear. Desired species and sizes can be targeted through trap design and the choice of bait. Size of the catch is affected by trap size, bait quantity and ...

Range, Activity, and Habitat of Large, Free‐Ranging Brown Trout in a Michigan Stream

Abstract: Little is known about behavior patterns and habitat use of large (400+ mm total length) brown trout Salmo trutta. We used radio telemetry to monitor the movements of eight large (437–635 mm), free-ranging brown trout for up to 346 d. Total range of movement upstream and downstream varied from 370 m to 33,420 m. At some time during the year, six of the fish moved out of an area protected with no-kill fishing regulations, even though none of them were tagged and released closer than 2 km from its boundaries. However, four of five fish tracked during the height of the fishing season spent 87% of their time in the protected area. The fish appeared to have separate winter and summer ranges. Five of six fish tracked during autumn–winter moved upstream about 10 km to slower, deeper parts of the river between August and November, and remained there at least through the following April. The part of the river used as autumn–winter range was considered only marginal habitat for brown trout during summer due...

A Stratified Random Transect Design for Acoustic Surveys of Fish Stocks

Abstract: The differences between design-based and model-based inference are examined briefly and some recent applications of model-based procedures in fishery surveys are discussed. It is shown that valid e...

Causes of Density-Dependent Catchability for Georges Bank Haddock Melanogrammus aeglefinus

Abstract: We used population estimates (VPA) fishing effort and catch data for Georges Bank haddock, Melanogrammus aeglefinus, from 1964 through 1984 to test Paloheimo and Dickie's hypothesis which predicts: (1) that the catchability coefficient (q) from the commercial fishery is inversely related to haddock stock size (N) and stock area (Area); (2) that commercial catch per effort (C/f) data are curvilinearly related to stock abundance; and (3) that search time in the Georges Bank haddock fishery is inversely related to stock abundance. The catchability coefficients for the Georges Bank trawl fishery were inversely related to haddock stock size (r = −0.82, P < 0.001) and stock area (r = −0.75, P < 0.001). There was also a significant curvilinear relationship between commercial C/f and absolute and relative haddock stock biomass from 1964 through 1984. The slope estimate (B + 1) from this relationship was less than 1.0 (r = 4.18 to 8.95, P < 0.001), indicating nonlinearity between C/f and N. Finally, the relative s...

Small marine pelagic fish and the threat of fishing; are they endangered?

Abstract: Evidence of the collapse and recovery of major marine fisheries for pelagic fish species is reviewed, distinguishing the influence of fishing compared with natural (environmental) effects. In one only of the best documented cases (Icelandic spring-spawning herring) has the stock failed to reappear, after 20 years. Several others, e.g. California sardine, have persisted at 1/000th or possibly less of their peak size for some years before beginning to recover. Fishing has been the main cause of collapse in most but not all cases, due initially to the escalation of catchability as stock size decreases–a phenomenon characteristic of fisheries for pelagic species due to their shoaling habit, ease of detection and vulnerability to modern fishing methods. It is concluded that although the threat of fishing to the continuity of the species is remote, excessive depletion (although avoidable by firm and timely management) is potentially able to cause temporary disappearance of local stock and disruption of the ecosystem.

Definition and Classification of Fishing Gear Categories

Abstract: Defenition and Classification of Fishing Gear Categories , Defenition and Classification of Fishing Gear Categories , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Eutrophication and Baltic fish communities

Abstract: The discharge of nutrients to the Baltic Sea has increased considerably during the 20th century. There are several indications that this eutrophication has affected the fish community. Changes in species composition have been reported from coastal areas, e.g. local increases in the abundance of pikeperch and decreases in whitefish. Total fish catches, dominated by herring, sprat, and cod, have increased tenfold in the past fifty years and doubled in the last twenty-five years. This increase is mainly due to intensified fishing, but possibly also to eutrophication and decreased fish predation by seals.

Lake Trout, Sea Lampreys, and Overfishing in the Upper Great Lakes: A Review and Reanalysis

Abstract: To assess the role of commercial fishing in the destruction of lake trout Salvelinus namaycush in Lakes Huron, Michigan, and Superior in the 1940s and 1950s, we reviewed the literature and analyzed catch and effort data for U.S. waters by regression analysis. There is abundant evidence of the effect of the sea lamprey Petromyzon marinus in the destruction of lake trout, but some have claimed that fishing also was influential. We considered that a persistent, significant decrease in catch per unit of effort before and in the first few years after the sea lamprey was first found in a lake would be evidence of overfishing. We found no convincing evidence of overfishing in Lakes Huron and Michigan. Lake trout probably were overfished in Lake Superior before the sea lamprey became a major influence. We conclude that statements that lake trout were destroyed in Lake Huron or Lake Michigan by a combination of overfishing and the sea lamprey are not justified. The same claim applied simply to the Great L...

Comparison of Job Satisfaction in Six New Jersey Fisheries: Implications for Management

Abstract: New Jersey's marine fisheries exhibit unusual diversity within a small geographical area-contrasting in terms of prey species, gear size and type, trip duration, seasonality, regulatory policies, and income levels. One might expect these differences to engender different patterns of job satisfaction. Based on a survey of several hundred fishermen, the paper compares baymen, oystermen, sea clarnmers, scallopers, draggers, and longliners with respect to thirty-three components of job satisfaction. Results show significant group-group contrasts in the nonmonetary rewards derived from fishing, even though all those surveyed were clearly commercial fishermen. One implication of these findings is that different regulatory tactics should be used if and when additional regulation of the fisheries becomes necessary.

The Effect of Illegal Harvest on Recreational Fisheries

Abstract: The degree of compliance with a fishing regulation can have a significant impact on the regulation's effectiveness. In this paper, we use a yield-per-recruit simulation model to evaluate the effect of poaching on legal harvest in sport fisheries. Two types of illegal harvest were considered: harvest of fish below the legal size limit and harvest of fish from catch-and-release fisheries. The results depict the degree of reduction in legal harvest in minimum-size fisheries with 0-100% (in 10% increments) illegal harvest. For brook trout Salvelinus fontinalis, the reduction in legal harvest ranged from 11% at 10% illegal harvest to 72% at 100% illegal harvest; these reductions ranged from 10 to 66% for northern pike Esox lucius, 8 to 57% for brown trout Salmo trutta, and 2 to 22% for largemouth bass Micropterus salmoides. In catch-and-release fisheries, illegal harvest reduces the number offish caught and released. Most ofthe benefits ofcatch-and-release regulations, in terms of increased numbers an...

Fishing with electricity: applications in freshwater fisheries management

Abstract: The history electric fishing electrophysiology of fish in electric fields electric fishing apparatus and electric fields facros affecting the efficiency of electric fishing electric fishing for sampling and stock assessment electric screens and guides electric fishing and safety electric fishing in practice - what does the future hold?

Fisheries ecololgy and management of the Jaraqui (Semaprochilodus Taeniurus, S. Insignis) in central Amazonia

Abstract: The decline of heavily exploited stocks of large, high quality, food fishes in central Amazonia has led to increasing fishing pressure on smaller taxa, especially the jaraqui (Semiprochilodus spp.). The Prochilodontids, now the most important species to the fisheries, are seined by commercial fishermen during three distinct peridos. At the beginning of the annual floods, schools of mature jaraquis in poor-water tributaries migrate downstream to spawn in the nutrient rich white-water rivers. During these rapid spawning runs, fishing effort is concentrated in the lowermost reaches of the tributaries. After spawning, they return in small groups to feed intensively in the flooded forest of the same tributaries from which they had migrated. This period, of approximately three months, may be considered as a natural closed season to the fisheries. The dispersal migration is most complex and requires distinct fishing strategies. In the middle of the floods large schools of fat jaraqui descend from the tributaries to the white-water rivers again. From there, they move upstream to different poor-water tributaries. As downstream movements are more diffcult to observe, fishermen remain at fixed fishing grounds. This contrasts with the dynamic strategies of the subsequent upstream fishing period which contributes 60 per cent of the annual catches. Fluctuations in catch are shown to reflect year to year variations in abundance, which are linked to the hydrological cycle. Considering that fishing over the stocks of jaraqui has already more than compensated for the deficit in catch of larger species, a combination of increased effort and environmental problems could lead, in a short period to a depletion of one of the most profitable fisheries of central Amazonia. Regulation of the fisheries could benefit from a more reasonable distribution of effort among other migratory illiophagous species which remain unexploited, if the goal of sustainable yield and conservation of these stocks is to be achieved. Reserved waters in large strategic units of at least 300 km along white-water rivers (which is equivalent to the maximum upstream displacement of jaraqui during their dispersal migrations) could also be useful to compensate for the loss of floodplain areas due to deforestaion, river regulation, use of pesticides, and mining. River impoundments in tributaries in central Amazonia may have little effect on jaraqui stocks, as spwning movements are unlikely to be directly interrupted by dams. However, alterations of the hydrological regime may also benefit from simulation of the flood cycle to mitigate potential negative impacts.

Partitioning of material discarded from prawn trawlers in Moreton Bay

Abstract: Prawn trawlers in Moreton Bay, Queensland, discard about 3000 t of material each year. About 3% floats, and the rest sinks. The floating component is almost entirely fish. At night, floating discards are eaten by silver gulls (Larus novaehollandiae), crested terns (Sterna bergii) and, to a lesser extent, dolphins (Tursiops truncatus). There is little trawling during the day but the last discards are dumped overboard around dawn. At this time cormorants (Phalacrocorax varius) join the scavengers. Birds and dolphins scavenged only fish and cephalopods, and not crustaceans nor echinoderms. Birds are selective as to the size of fish they will eat, but most of the whole fish in the discards are below 50 g, and the largest fish that crested terns ate was 100 g. Dolphins are capable of taking the largest of the discarded fish. Most of the material that sinks is crustaceans (54%) and echinoderms (18%); the rest is elasmo- branchs and rubble. At night, about half of the fish that sink are eaten by diving birds and by dolphins. There was no indication of mid-water scavenging of sinking discards, except for cormorants and dolphins in the upper water column. Approximately 11% of the discards that reach the bottom comprise fish and crustaceans, which are eaten by crabs (Portunus pelagicus) and fish. The remainder- chiefly crabs, echinoderms and elasmobranchs-reach the bottom alive. Altogether, about 20% of discards are eaten by surface and bottom scavengers. Discards are probably important in maintaining populations of the major scavengers.

The Delimitation of Fishing Areas in the Northwest Atlantic

Abstract: The delineation of geographic areas for the purpose of collecting fisheries statistics (referred to as "fishing areas") in the Northwest Atlantic is described from the first division by the North American Council on Fishery Investigations in the early-1930s, through development of the International Commission for the Northwest Atlantic Fisheries statistical system in the early-1950s, to the present Northwest Atlantic Fisheries Organization (NAFO) system. The bases for these fishing areas are examined, and, in particular, knowledge of biological stock structure at crucial decision points is reconstructed, to determine the extent to which fishing areas were designed to correspond to stock distribution areas of the important commercial species. This correspondence is also examined in the light of present knowledge of stock structure. It transpires that only cod and haddock stock structure is documented as being influential in statistical boundary determination. The present NAFO statistical grid system could be improved, particularly by incorporation of the boundaries between coastal state and NAFO Regulatory Area waters, but is basically too inflexible to serve the needs of diverse modern fisheries. A hierarchical system, with the basic unit being a 10' or 15' graticule,as has already been adopted by some countries for domestic statistics, should be established in the international context of NAFO to promote regional science and management initiatives. Biologists need to define more precisely the correspondence required between stock and management areas for the effective control of exploitation rates.

Variation in the Competitive Abilities of Fishermen and its Influence on the Spatial Distribution of the British Columbia Salmon Troll Fleet

Abstract: We estimated the catch rates of individual fishing vessels within the British Columbia salmon troll fleet from the data of a 7-yr log book program. Catch rates varied considerably among vessels. A ...

Developments in electric fishing

Abstract: Electrophysiology of fish in electric fields electric fishing apparatus factors affecting the efficiency of electric fishing sampling and stock assessment by electric fishing electric fishing screens and guides safety in electric fishing.

A review of ghost fishing by traps and gillnets

Abstract: Ghost fishing occurs when lost fishing gear continues to catch and kill animals. This paper reviews what is known about ghost fishing in trap and gillnet fisheries, how the information was obtained and how it has been used, how ghost fishing can be prevented, and what regulatory approaches have been taken to address the problem. Some standard terms are proposed to prevent confusion. Ghost fishing by traps can occur through several mechanisms. The problem is serious in several fisheries, minor in at least one, and remains unexamined for the majority of trap fisheries. Timed-release devices are simple, inexpensive, and effective at preventing ghost fishing by opening the trap some time after loss. In all Dungeness crab fisheries, such devices are required in crab traps, and other regulations attempt to minimize trap loss. In the American lobster fishery, only Connecticut and Maine address ghost fishing, which is known to be a problem. Ghost fishing by traps is poorly recognized as a problem outside North America.

A fishery-dependent based study of fish species composition and associated catch rates around oil and gas structures off Louisiana

Abstract: The impact of oil and gas development on fish populations off Louisiana is presumed significant but poorly understood. This study was undertaken to determine the applicability of a logbook program in developing a long-term database of species composition and relative abundance of fish associated with oil and gas structures. A pilot logbook program involving 120 private vessel owners and 25 charterboat operators was conducted between March 1987 and December 1988. Participants recorded date, fishing time, fishing method, number of anglers, and catch composition at each structure fished. Logbooks from a total of 55 private vessel owners and 10 charterboat operators were used in the analysis. Data collected included 15,780 angler hours of fishing effort and 61,227 fish caught over the study period. A total of 1,719 trips were made to 589 different oil and gas structures with at least 46 different species of fish caught. Red snapper and spotted seatrout were the most commonly caught species and had the highest catch rates. Results differed from past logbook programs and creel surveys, possibly indicating a change in the community of fish associated with oil and gas structures.

Onshore-offshore patterns of human fishing activity.

Abstract: Current evidence suggests that major morphological innovations in marine animals appeared in nearshore environments and then expanded offshore. As with durophagous predators that evolved late in the Mesozoic, the impact of Homo sapiens is most strongly felt first in onshore benthic communities. Fishing activity worldwide has begun in nearshore environments and then expanded offshore. The community changes wrought by removing predatory (and sometimes herbivorous) teleosts follow the onshore-offshore pattern. Humans are transforming nearshore benthic communities to

Manipulation of Fishing Effort in Australia's Penaeid Prawn Fisheries

Abstract: The potentially detrimental side-effects of prawn trawling are coming under increasing scrutiny in Australian waters, particularly in such ecologically sensitive areas as Queensland's Great Barrier Reef, and various restrictive measures are being suggested. Before changes are imposed on the prawning industry, the effects of trawling on the target prawn species and the long-term management of these effects need to be fully understood. Using a simulation model of a simplified prawn fishery, this paper describes the basis for the current regulatory mechanisms for Australian's prawn fisheries, in particular the manipulation of both the level and pattern of fishing effort. It is shown that even in moderately fished stocks, the fishery manager has several options, such as seasonal and nursery area closures, that are consistent with the goal of minimizing the impact of prawn trawling, while in no way penalizing the industry economically. With these in mind, possible ways of resolving or reducing the conflict with groups outside the prawning industry are discussed.

The New England Groundfish Fishery after 10 Years under the Magnuson Fishery Conservation and Management Act

Abstract: In the first 10 years under the Magnuson Fishery Conservation and Management Act, the New England and Mid-Atlantic regional fishery management councils (FMCS) managed 19 species of finfish and shellfish under eight fisheries management plans. The ability of the councils to effectively manage marine fisheries can be demonstrated by examining the management plans and levels of catch, and by noting the condition of the resource. Heavy foreign fishing during the 1960s and early 1970s was constrained by catch quotas imposed by the International Commission for Northwest Atlantic Fisheries, and the abundance of principal groundfish increased significantly by 1978. From 1976 to 1983, New England fishing effort doubled, and stocks that had not been heavily fished by foreign fleets went from being underfished to being overfished in just a few years. The total U.S. catch of finfish and squids steadily increased from 1973 to 1980 and then declined. The original Groundfish Plan was only for Atlantic cod Gadus...