Blue and Mako Shark by-catch in the Japanese Longline Fishery off South-eastern Australia

1992 ◽  
Vol 43 (1) ◽  
pp. 227 ◽  
Author(s):  
JD Stevens
Keyword(s):  
Bluefin Tuna ◽  
Fishing Effort ◽  
Adolescent Females ◽  
Actual Number ◽  
Mako Shark ◽  
Shortfin Mako ◽  
Eastern Australia ◽  
Southern Bluefin Tuna ◽  
By Catch ◽  
Catch Rates

During the last 10 years, up to 70 Japanese longline vessels have fished Tasmanian waters of the Australian Fishing Zone each season, targeting bluefin tuna (Thunnus maccoyii). The average seasonal fishing effort in Tasmanian waters is about 3.3 million hooks, and data from observers suggests that, this results in a by-catch of some 34 000 blue sharks (Prionace glauca) each year, representing a weight of about 275 tonnes. In the last few years, fishing effort has increased as the catch rates of southern bluefin tuna have declined. The sharks are discarded after removal of the fins. The actual number of blue sharks hooked is much higher than 34000 because many are released by either shaking or cutting them off the line, although they are often damaged in the process. The majority of blue sharks caught are immature or adolescent females. Smaller numbers of shortfin mako sharks (Isurus oxyrinchus) are also caught and retained both for their fins and their meat. Tasmanian waters represent only one area of the Australian Fishing Zone fished by Japanese longliners.

Likely impacts of an eastward expansion of the inshore gill-net fishery in the Western Cape, South Africa: implications for management

2003 ◽  
Vol 54 (1) ◽  
pp. 39 ◽  
Author(s):  
K. Hutchings ◽  
S. J. Lamberth
Keyword(s):  
West Coast ◽  
Fishing Effort ◽  
Western Cape ◽  
Catch Per Unit Effort ◽  
South West ◽  
Gill Net ◽  
South West Coast ◽  
By Catch ◽  
Catch Rates ◽  
The Impact

Current South African government policy aims to create more equitable access to marine resources and there is pressure to increase the inshore gill-net fishing effort. At present, the gill-net fishery in the Western Cape is confined to the cool temperate west coast. In order to ascertain the potential catch if the fishery was to expand along the warm temperate south-west coast, a program of experimental netting was conducted. Estuarine and coastal marine sites were sampled bimonthly, using a range of commercial gill-nets (44–178 mm stretch-mesh). Although the target species, Liza richardsonii, dominated the catches, at least 33 of the by-catch species caught were also targeted by the commercial or recreational line-fish sectors. The number of species captured and the line-fish (by-catch) catch per unit effort (CPUE) were greatest in areas currently closed to the commercial gill-net fishery. Multivariate analysis indicated significant differences in catch rates and composition between exploited west coast and unexploited south-west coast sites. A combination of natural biogeographical trends and the impact of over 100 years of commercial gill-netting on the west coast are the likely causes of these differences. A spatial expansion of the gill-net fishery could have a detrimental impact on overexploited line-fish stocks and lead to increased user conflict.

Evaluating empirical indicators and reference points for fisheries management: application to the broadbill swordfish fishery off eastern Australia

2001 ◽  
Vol 52 (6) ◽  
pp. 819 ◽  
Author(s):  
André E. Punt ◽  
Robert A. Campbell ◽  
Anthony D. M. Smith
Keyword(s):  
Length Distribution ◽  
Fishing Effort ◽  
Reference Points ◽  
Current Status ◽  
Stock Structure ◽  
Eastern Australia ◽  
Stock Assessments ◽  
Management Application ◽  
The Mean ◽  
Catch Rates

Calls to use target, limit and threshold reference points to achieve precautionary management goals have increased substantially in recent years. For many fisheries there is little chance of conducting formal stock assessments, and indicators of stock status have to be based on changes in measurable quantities such as catch rates and percentiles of the length distribution of the catch. Use of such empirical indicators for management decisions also requires a choice of appropriate reference or trigger levels for the indicators. Monte Carlo simulation can be used to examine the performance of alternative indicators and associated reference points in terms of their ability to correctly identify the biological conditions that they were designed to measure. This study examines the performance of several potential empirical indicators for broadbill swordfish off eastern Australia, taking into account uncertainties in stock structure, current status, and future trends in fishing effort. Indicators based on catch rates are shown to be potentially very misleading. In contrast, indicators based on the mean length or mean weight of the catch perform better, because these quantities change in a more predictable manner with abundance. Nevertheless, reference points based on these quantities are frequently ‘triggered’ either too early or too late.

Monitoring the recreational gamefish fishery off south-eastern Australia

2003 ◽  
Vol 54 (4) ◽  
pp. 425 ◽  
Author(s):  
Michael Lowry ◽  
Jeff Murphy
Keyword(s):  
Spatial Distribution ◽  
Monitoring Program ◽  
Fishing Effort ◽  
Target Species ◽  
Eastern Australia ◽  
Species Groups ◽  
Catch Rates ◽  
Catch Composition ◽  
The Impact ◽  
Integrated Program

The east coast Australian gamefish fishery is a diverse, multi-species fishery that targets billfish, sharks, tuna and other pelagic fish along the east Australian seaboard. A Gamefish Tournament Monitoring Program (GTMP) was undertaken, and 39021 angler trips from 1996 to 2000 were analysed. The program reports on trends in fishing effort, catch rates, catch composition, proportions of captures tagged and released and spatial distribution of catches for the principal recreational billfish species: black marlin (Makaira indica), striped marlin (Tetrapterus audax) and blue marlin (Makiara nigricans).The GTMP was principally designed as part of an integrated program to monitor the recreational gamefish fishery. The spatial and temporal design of the program restricted statistical analyses however, there were trends in fishing effort, directed effort, catch rates, catch composition, proportions of fish tagged and spatial distribution of catches for the principal recreational billfish species over seven successive years (1994–2000). Analysis of catch data, stratified by directed effort, indicated significant differences in catches of target species, demonstrating the importance of calculating catch rate estimates according to the main target preference. Analysis of tournament based tagging information indicated that while overall tournament tagging rates remained high (88%) there were significant differences in the number of fish tagged between species groups highlighting the impact that angler attitude and the competition point score structure has on the harvest of gamefish target species.

Horizontal and vertical movements of the shortfin mako shark, Isurus oxyrinchus, in the Southern California Bight

1993 ◽  
Vol 44 (6) ◽  
pp. 901 ◽  
Author(s):  
DB Holts ◽  
DW Bedford
Keyword(s):  
Southern California ◽  
Bottom Topography ◽  
Fishing Effort ◽  
Southern California Bight ◽  
Diel Activity ◽  
Commercial Fishing ◽  
Vertical Movements ◽  
Mako Shark ◽  
Isurus Oxyrinchus ◽  
Shortfin Mako

Recreational and commercial fishing effort directed at the shortfin mako shark, Isurus oxyrinchus, off the coast of southern California increased markedly in the mid 1980s. However, very little is known about the population size, stock structure or movements of these sharks in the northern Pacific. It is important to determine their role in these waters because the southern California bight may be an important pupping and nursery area for shortfin mako sharks. Acoustic telemetry was used to identify short-term horizontal and vertical movements of three shortfin mako sharks in the southern California bight during the summer of 1989. All three sharks were two-year-old juveniles and were tracked for periods of from 18 to 25 h. They spent 90% of their time in the mixed layer, with only infrequent excursions below the thermocline. Vertical and horizontal movements did not indicate any diel activity pattern associated with distance to the shore or nearby islands or with bottom topography.

Fish and invertebrate by-catch in the crab pot fishery in the Isle of Man, Irish Sea

2017 ◽  
Vol 98 (8) ◽  
pp. 2099-2111
Author(s):  
Fikret Öndes ◽  
Michel J. Kaiser ◽  
Lee G. Murray
Keyword(s):  
Irish Sea ◽  
Target Species ◽  
Catch Per Unit Effort ◽  
Isle Of Man ◽  
Ecosystem Effects ◽  
By Catch ◽  
Catch Rates ◽  
Taxonomic Groups ◽  
Catch Composition ◽  
Autumn And Winter

Baited trap or pot fisheries are considered to have relatively few wider ecosystem effects on the marine environment, particularly when compared with towed mobile fishing gear. However, this assumption is rarely tested in the field. This study aimed to determine the composition of non-target species that occur in crustacean pots and to assess spatial and temporal differences in catches in the waters around the Isle of Man, Irish Sea. The data were collected using fishery independent surveys and a questionnaire study. Based on fishery independent surveys, a total of five taxonomic groups and 43 species occurred as by-catch. The dominant by-catch species was velvet crab Necora puber. The by-catch per unit effort (BPUE) for all of the non-target species was low particularly in comparison to towed bottom gear fisheries around the Isle of Man. BPUE of species composition varied considerably between different locations around the Isle of Man. The results of both the fishery independent and questionnaire data suggested that the by-catch rates varied with season with peak BPUE occurring in spring which then declined into autumn and winter. By-catch composition did not decrease significantly with an increasing target species catch. Overall, by-catch was low relative to target species catch which may be partially attributable to the use of escape panels in pot fisheries in the Isle of Man.

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