Survival of Atlantic Halibut (Hippoglossus hippoglossus) Caught by Longline and Otter Trawl Gear

1989 ◽  
Vol 46 (5) ◽  
pp. 887-897 ◽  
Author(s):  
John D. Neilson ◽  
Kenneth G. Waiwood ◽  
Stephen J. Smith
Keyword(s):  
Handling Time ◽  
Bottom Trawl ◽  
Minimum Size ◽  
Otter Trawl ◽  
Fish Length ◽  
Atlantic Halibut ◽  
Small Fish ◽  
Total Catch ◽  
Hippoglossus Hippoglossus ◽  
Size Limit

To assess the effectiveness of a proposed minimum size limit (81 cm) for Atlantic halibut (Hippoglossus hippoglossus) in Canadian waters, the survival of small fish caught in longline and bottom trawl gear was examined using live holding facilities onboard a research vessel and subsequently, in a land-based laboratory. Commercial practices were simulated during fishing operations. Of halibut less than the proposed size limit, 35% of the otter trawl catch and 77% of the longline catch survived more than 48 h. Factors potentially influencing halibut survival (handling time, total catch, fish length, maximum depth fished, and trawl duration) were examined using proportional hazard models. On the basis of those analyses, it was concluded that in bottom trawl sets of duration used in the commercial fishery (≥ 2 h), higher survival times were associated with shorter handling time, larger fish size, and comparatively small total catch weight. Supplemental information on the condition of trawl-caught halibut was also obtained from observers stationed onboard commercial trawlers.

Minimum Size Regulations and the Implications for Yield and Value in the Canadian Atlantic Halibut (Hippoglossus hippoglossus) Fishery

1989 ◽  
Vol 46 (11) ◽  
pp. 1899-1903 ◽  
Author(s):  
John D. Neilson ◽  
W. R. Bowering
Keyword(s):  
Mortality Rate ◽  
Size Composition ◽  
Minimum Size ◽  
Atlantic Halibut ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Hippoglossus Hippoglossus ◽  
Size Regulation ◽  
Size Limit ◽  
Yield Per Recruit

The effect of a minimum size regulation on yield and value per recruit in the Canadian Atlantic halibut fishery was examined. The model indicated that under most scenarios, the size limit would not result in increased yield per recruit. In general, yield per recruit was more sensitive to fishing mortality than age of first entry to the fishery. While reduced yields were usually associated with the minimum size limit, the value per recruit increased with increasing age at entry to the fishery until age 7. The changes in value per recruit reflected the size composition of landings following the imposition of the size limit and the different values associated with various size categories. Both yield and value per recruit were sensitive to the choice of the natural mortality rate.

Paddlefish Management, Propagation, and Conservation in the 21st Century

2009 ◽  
Keyword(s):  
Fork Length ◽  
Handling Time ◽  
Minimum Size ◽  
Fish Length ◽  
Fishing Mortality ◽  
Reasonable Approach ◽  
Radio Transmitters ◽  
Early Fall ◽  
Delayed Mortality ◽  
Size Limits

<em>Abstract</em>.—We present information on delayed mortality of commercially exploited paddlefish <em>Polyodon spathula </em>released as bycatch in Kentucky Lake, Tennessee–Kentucky, an impoundment on the lower Tennessee River. Minimum size limits enacted in 2002 (864 mm eye-to-fork length [EFL]) and 2005 (914 mm EFL) sought to protect paddlefish from overfishing. In 2005, bycatch of sublegal paddlefish represented 75% of the total catch, and releasing undersized fish will not reduce fishing mortality unless those fish survive. Paddlefish caught and released by commercial fishers in 2005 and 2006 were externally tagged with radio transmitters and tracked a minimum of 2 weeks to estimate delayed mortality. Four of the 104 tagged paddlefish died following release, 94 survived, and 6 were censored because their fate could not be determined. Paddlefish that survived moved rapidly from release locations. Net movements of the 94 fish that survived averaged 12.0 km (SE = 5.3) upriver and ranged from 91.5 km downriver to 390.0 km upriver. Fish that died could not be distinguished from fish that lived on the basis of mean water temperature, fish length, net-soak time, or handling time. Given the low delayed mortality of discarded paddlefish, imposing minimum size limits is a reasonable approach to reduce fishing mortality of juveniles and reduce the likelihood of overfishing. Efforts to reduce fishing mortality should focus on avoiding fishing gear and seasons (e.g., early fall and late spring) that cause high initial bycatch mortality.

Optimal prey size for stream resident brown trout (Salmo trutta): tests of predictive models

1986 ◽  
Vol 64 (3) ◽  
pp. 704-713 ◽  
Author(s):  
Eileen Bannon ◽  
Neil H. Ringler
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Prey Size ◽  
Food Resource ◽  
Handling Time ◽  
Minimum Size ◽  
Small Fish ◽  
Order Stream ◽  
Mouth Size ◽  
Brown Trout Salmo Trutta

The time required to handle different-sized prey (crickets) was measured in an artificial stream for eight wild brown trout (Salmo trutta L.) in two size classes (mean total lengths, 186 and 214 mm). Handling times (HTs) scaled by mouth size were described by an exponential equation: HT = 1 + 0.84e2.35(ps/ms) (ps, prey size; ms, predator (mouth) size). Cost curves based on handling time/prey weight were used to predict optimal prey lengths of 22 mm for small trout and 24 mm for large trout. A second model based on J. W. J. Wankowski's empirical results predicted slightly smaller optima. Physical constraints provided estimated minimum prey lengths of 2.8 and 3.2 mm for large and small fish, respectively; maximum prey lengths were 89 and 97 mm, respectively. We compared the predicted optimal prey size with the size distribution of invertebrates in drift and brown trout stomachs sampled in a second-order stream from July to September 1982. The most abundant prey sizes in the study stream were near the minimum size that can be effectively handled by brown trout. Prey of the predicted optimum size were rare, but feeding was size selective in spite of a limited food resource. The growth rates of these stream-dwelling brown trout were slower than the brown trout in other streams in this region. This may reflect diets consisting largely of suboptimal-sized prey.

scholarly journals The recovery of Atlantic halibut: a large, long-lived, and exploited marine predator

2016 ◽  
Vol 73 (4) ◽  
pp. 1104-1114 ◽  
Author(s):  
M. Kurtis Trzcinski ◽  
W. Don Bowen
Keyword(s):  
Gadus Morhua ◽  
Assessment Model ◽  
Minimum Size ◽  
Otter Trawl ◽  
Atlantic Halibut ◽  
High Biomass ◽  
Total Allowable Catch ◽  
Marine Predator ◽  
Trawl Fishery ◽  
Management Actions

Abstract Atlantic halibut (Hippoglossus hippoglossus) have a long history of exploitation in the Northwest Atlantic and have gone through several periods of high biomass followed by a population crash. An assessment model using data collected on the Scotian Shelf and southern Grand Banks shows that the population peaked in 1984, then decreased sharply to a low in 1993. Several management measures were taken during the decline, including reductions in total allowable catch and a minimum size limit. Concurrently, removals by the otter trawl fishery were drastically reduced following the collapse of the cod (Gadus morhua) fishery. In 2003, recruitment increased and continued to be high for 6 years. Fishing mortality rates were moderate in the late 1990s and 2000s and the population increased. By 2009, the Atlantic halibut population was highly productive with both high biomass and high levels of recruitment. The coincidence in the timing of population recovery and management actions indicates that effective management contributed to the recovery of Atlantic halibut.

scholarly journals Diurnal variation in bottom trawl survey catches: does it pay to adjust?

2002 ◽  
Vol 59 (1) ◽  
pp. 33-48 ◽  
Author(s):  
Vidar Hjellvik ◽  
Olav Rune Godø ◽  
Dag Tjøstheim
Keyword(s):  
Correction Term ◽  
Bottom Trawl ◽  
Melanogrammus Aeglefinus ◽  
Fish Length ◽  
Small Fish ◽  
Trawl Survey ◽  
Moderate Increase ◽  
Bottom Trawl Survey ◽  
Abundance Estimate ◽  
Diurnal Amplitude

The diurnal bias of bottom trawl survey catches is studied with the purpose of adjusting for it and thereby improving the accuracy of abundance estimates. The correction term is estimated with uncertainty and thus increases the variance of the resulting abundance estimate. To investigate this adequately, we use a stochastic model describing diurnal fluctuations and examine the annual variation of the diurnal amplitude as a function of species and length. The diurnal amplitude is fairly stable for large fish, and for these, the bias-corrected estimate leads to a moderate increase in variance. For small fish, the diurnal amplitude is unstable, however, and the correction of diurnal bias occurs at the expense of a large increase in variance. This unstable amplitude also leads to a large year-to-year variation in catchability for small fish. For haddock (Melanogrammus aeglefinus), the diurnal amplitude depends heavily on fish length, indicating a strong decrease in catchability with decreasing fish length.

Helminth parasites of the alimentary tract of Atlantic halibut (Hippoglossus hippoglossus L.) and Greenland halibut (Reinhardtius hippoglossoides (Walbaum)) on the Scotian Shelf

1989 ◽  
Vol 67 (6) ◽  
pp. 1476-1481 ◽  
Author(s):  
James S. Scott ◽  
Shelley A. Bray
Keyword(s):  
Parasite Prevalence ◽  
Fish Length ◽  
Atlantic Halibut ◽  
Helminth Parasites ◽  
Intermediate Hosts ◽  
Scotian Shelf ◽  
Greenland Halibut ◽  
Hippoglossus Hippoglossus ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
Reinhardtius Hippoglossoides

Examination of the alimentary tracts of 272 Atlantic halibut (Hippoglossus hippoglossus (L.)) and 71 Greenland halibut (Reinhardtius hippoglossoides (Walbaum)) from the Scotian Shelf yielded a total of 25 helminth parasite species, 23 from H. hippoglossus (16 Digenea, 3 Cestoda, 2 Acanthocephala, 2 Nematoda) and 16 from R. hippoglossoides (11 Digenea, 3 Cestoda, 1 Acanthocephala, 1 Nematoda). Parasite prevalence and intensity were low (< 50% and < 10%, respectively) in both hosts, except for Derogenes varicus and Steganoderma formosum in H. hippoglossus and anisakid nematodes in R. hippoglossoides. Consideration of change in parasite prevalence and mean intensity in relation to fish length and diet suggests fish prey as transport hosts for D. varicus in larger halibuts, and crustaceans as the intermediate hosts for S. formosum before transmission to its principal host, H. hippoglossus. Geographical change in parasite prevalence and intensity was in the form of southwest to northeast clines along the Shelf, probably related to environmental factors. There was no evidence for stock differentiation in either of the hosts based on parasite fauna.

Size at Maturity, Spawning Season, and Food of Atlantic Halibut

1967 ◽  
Vol 24 (1) ◽  
pp. 53-66 ◽  
Author(s):  
A. C. Kohler
Keyword(s):  
Spawning Season ◽  
Otter Trawl ◽  
Atlantic Halibut ◽  
Size At Maturity ◽  
Hippoglossus Hippoglossus ◽  
Trawl Catches

In otter-trawl catches of Atlantic halibut (Hippoglossus hippoglossus L.) by research vessels from 1959 to 1964, mature males less than 66 to 70 cm long were not regularly encountered. Males were 96 to 100 cm long before the majority were mature, and females slightly longer. The research catches and commercial samples taken by longline from 1961 to 1963 indicated that spawning occurred at various times during the first half of the year. Halibut up to 30 cm long ate invertebrates; from 30 to 80 cm, invertebrates and fish; and over 80 cm, fish almost exclusively.

Survival of Atlantic halibut (Hippoglossus hippoglossus) following catch-and-release angling

2017 ◽  
Vol 186 ◽  
pp. 634-641 ◽  
Author(s):  
Keno Ferter ◽  
Audun H. Rikardsen ◽  
Tor H. Evensen ◽  
Martin-A. Svenning ◽  
Sean R. Tracey
Keyword(s):  
Atlantic Halibut ◽  
Hippoglossus Hippoglossus ◽  
Catch And Release
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