Further Perspectives on Yield per Recruit Analysis and Biological Reference Points

1991 ◽  
Vol 48 (12) ◽  
pp. 2533-2542 ◽  
Author(s):  
James G. Norris
Keyword(s):  
Fishing Effort ◽  
Reference Points ◽  
Alternative Methods ◽  
Optimal Method ◽  
Straight Line ◽  
Gear Selectivity ◽  
Critical Age ◽  
By Catch ◽  
Yield Per Recruit ◽  
Spawning Biomass

Spawner–recruit relationships (SRRs) are indeterminate for most species. Earlier workers proposed solving "amount of harvest" problems for such cases by tacitly assuming that the SRR is density independent (a straight line through the origin) for the available data. I extend that concept and demonstrate a technique for solving "method of harvest" problems when the SRR is indeterminate. This technique uses spawning biomass per recruit, rather than fishing effort, as the benchmark for comparing alternative methods of harvest. Yields from different harvesting methods are deemed comparable only when they produce the same spawning biomass per recruit. If the comparisons are consistent over the entire range of spawning biomass per recruit values, one can evaluate the relative merits of competing methods of harvest without the benefit of spawner–recruit data. Although this technique does not determine the optimal gear selectivity, it allows comparisons of sustainable yields from currently available gear types. The technique is particularly useful for analyzing fishery allocation and by-catch problems. Two life history parameters, critical age (age at which a cohort maximizes its biomass or dollar value) and the age at 50% sexual maturity, may be most important in determining the optimal method of harvest (fishing gear selectivity).

An Alternative Perspective on Recruitment Overfishing and Biological Reference Points

1987 ◽  
Vol 44 (4) ◽  
pp. 913-918 ◽  
Author(s):  
M. P. Sissenwine ◽  
J. G. Shepherd
Keyword(s):  
Fisheries Management ◽  
Reference Point ◽  
Reference Points ◽  
Fishing Mortality ◽  
Alternative Perspective ◽  
Conventional Models ◽  
Definition Of ◽  
Yield Per Recruit ◽  
Spawning Biomass

Biological reference points are used to guide fisheries management decisions. The reference points most often used are expressed in terms of fishing mortality rate (F). Fmsy relates to the maximization of sustainable yield. In principle, it is a most useful reference point, but in practice it is difficult to estimate. Fmax and F0.1 relate to certain levels of yield per recruit and are easily estimated, but they ignore conservation of the resource. Recruitment overfishing has usually been understood to occur when a population has been fished down to a point where recruitment is substantially reduced or fails. It has not been used as a basis for a biological reference point because the definition is vague and cannot be readily related to fishing mortality. Levels of spawning biomass below which recruitment seems to be reduced have been used, but their determination from available data is usually difficult and controversial. We propose an alternative definition of recruitment overfishing in terms of the level of fishing pressure that reduces the spawning biomass of a year class over its lifetime below the spawning biomass of its parents on average. Conventional models and types of data can be used to determine this level of F, denoted as Frep, which clearly relates to the replacement of spawning biomass and thus to sustainability of a population and yield in the long term.

scholarly journals Potential benefits from improved selectivity in the northwest Mediterranean multispecies trawl fishery

2007 ◽  
Vol 64 (4) ◽  
pp. 757-760 ◽  
Author(s):  
Nixon Bahamon ◽  
Francesc Sardà ◽  
Petri Suuronen
Keyword(s):  
Juvenile Fish ◽  
Fishing Effort ◽  
Trawl Fishery ◽  
Norway Lobster ◽  
Management Scheme ◽  
Large Numbers ◽  
Gear Selectivity ◽  
Potential Benefits ◽  
Yield Per Recruit ◽  
European Hake

Abstract Bahamon, N., Sardà, F., and Suuronen, P. 2007. Potential benefits from improved selectivity in the northwest Mediterranean multispecies trawl fishery. – ICES Journal of Marine Science, 64: 757–760. The management scheme in the northwest Mediterranean multispecies demersal fishery is based largely on technical measures such as minimum mesh and landing sizes. However, selectivity of the trawls used is poor, and large numbers of juvenile fish are caught. We assess the consequences of improved gear selectivity for European hake, Norway lobster, poor cod, and greater forkbeard by assuming that the whole fleet would switch from the current 40 mm diamond-mesh to a 40 mm square-mesh (SM40) codend. The results suggest that, immediately after implementation, the yield-per-recruit (Y/R) would be reduced by up to 20% for the three fish species but that, within five years, the Y/R of European hake would increase by > 50 %, provided fishing effort did not change markedly. For poor cod and greater forkbeard, the comparable increases would be more moderate, whereas for Norway lobster, the gains would only be small. Overall, marked long-term benefits might be obtained by changing to SM40 codends.

Comparison of reference points estimated using a size-based method for two high-latitude crab species in the United States and Canada

2004 ◽  
Vol 61 (8) ◽  
pp. 1404-1430 ◽  
Author(s):  
M SM Siddeek ◽  
Bernard Sainte-Marie ◽  
Jim Boutillier ◽  
Gretchen Bishop
Keyword(s):  
United States ◽  
High Latitude ◽  
The United States ◽  
Reference Points ◽  
Minimum Size ◽  
Snow Crab ◽  
Harvest Rate ◽  
Stock Recruitment ◽  
Dungeness Crabs ◽  
Spawning Biomass

We briefly reviewed the decision rules currently used for managing two major high-latitude crab stocks, snow crab (Chionoecetes opilio) and Dungeness crab (Cancer magister), in the United States and Canada and compared them with model-based reference points, harvest rate, and biomass proportion relative to virgin biomass, developed using species- and area-specific parameters. The model followed a size-based approach, which incorporated Beverton–Holt and Ricker stock–recruitment models and estimated mean and median reference points. The recruitment was also perturbed to generate distributions of reference points. The Beverton–Holt stock–recruitment model provided a lower harvest rate than that of the Ricker model. Harvest rates were lower for combined sexes spawning biomass than for female-only spawning biomass. Increasing the minimum size at first capture and decreasing the handling mortality resulted in increased harvest rates. Changes in fishery duration and timing of fishery open date did not change the harvest rate appreciably. The harvest rates for the Canadian snow and Dungeness crabs were mostly higher than those estimated for the Bering Sea and Southeast Alaska stocks. Reliable estimates of a number of life history parameters are lacking for both species, and hence, the results of this exercise need to be treated in a precautionary manner.

scholarly journals Stock dynamics of the brushtooth lizardfish Saurida undosquamis (Richardson, 1848) from a tropical multispecies fishery in the southeastern Arabian Sea

2019 ◽  
Vol 32 ◽  
pp. 9
Author(s):  
Theparambil Mohamed Najmudeen ◽  
Pallangattu Kochukandan Seetha ◽  
Payiyappanal Ulahannan Zacharia
Keyword(s):  
Arabian Sea ◽  
Growth Parameters ◽  
Total Mortality ◽  
Fishing Effort ◽  
Reference Points ◽  
Trophic Levels ◽  
Southeastern Arabian Sea ◽  
Eastern Arabian Sea ◽  
The Mean ◽  
First Maturity

The brushtooth lizardfish Saurida undosquamis (Richardson, 1848) is a high trophic level benthic predator and is one among the most exploited demersal finfish species from eastern Arabian Sea by Indian trawlers. However, in recent years, the landings of many top predator fishes including S. undosquamis showed a declining trend resulting in a steady decline in the mean trophic levels of the fishes caught commercially in the region. We investigated the growth, mortality and stock dynamics of S. undosquamis harvested by mechanised trawls in the southeastern Arabian Sea, using length-based methods for the data collected during 2012–2016. Besides, Bayesian state-space implementation of the Schaefer model (BSM) and catch-based MSY (CMSY) estimation were also made using the data for the period 1985–2016. Total length of the fish ranged from 5.5 to 34.5 cm with average annual mean length of 22.0 cm during 2012–2016. The growth parameters L∞ and K were 37.3 cm and 0.41 year−1, respectively. The natural, fishing and total mortality coefficients were 0.92, 2.58 and 3.5, respectively and exploitation ratio was 0.82. The length at first maturity was estimated at 21.4 cm for females. The mean size in the catch is lower than the optimum length for exploitation. Fisheries reference points (MSY, Fmsy, Bmsy) as well as relative stock size (B/Bmsy) and exploitation (F/Fmsy) estimated from catch data and broad priors for resilience (r), implies an exploitation of 30% below Bmsy level. Results from the length-based Thompson and Bell prediction model indicates that reducing the present level of fishing effort by 40% would lead to a harvest of the species at a sustainable level. As “fishing down food web” is reported in recent years from eastern Arabian Sea, the exploitation of top predators need to be maintained at sustainable levels to prevent ecosystem changes along the region.

scholarly journals Fisheries for the future: greenhouse gas emission consequences of different fishery reference points

2020 ◽  
Vol 77 (5) ◽  
pp. 1666-1671
Author(s):  
Sara Hornborg ◽  
Anthony D M Smith
Keyword(s):  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Greenhouse Gas Emission ◽  
Fuel Efficiency ◽  
Fishing Effort ◽  
Reference Points ◽  
Production Model ◽  
Fuel Use ◽  
Gas Emissions ◽  
Fishing Vessels

Abstract Global fisheries have for long been scrutinized in terms of ecosystem effects but only more recently for their greenhouse gas emissions. These emissions are dominated by fuel use on fishing vessels and the levels are often neglected side effects of resource overexploitation. Using a simple production model, Pella-Tomlinson, we illustrate how fuel efficiency (fuel use per unit of catch) varies with the level of exploitation and biomass depletion. For this model, fuel use per unit catch rises hyperbolically with fishing effort—it is relatively flat at low levels of effort but rises steeply as effort increases and biomass and catch decline. In light of these findings, the general fuel efficiency relationship with common fishery reference points on stock status is discussed, as well as other means of reducing fuel use and thus greenhouse gas emissions. We conclude that much may be gained by considering fuel efficiency in setting reference points for target stock biomass in fisheries and encourage further investigations.

scholarly journals The MINOUWApp: a web-based tool in support of by-catch and discards management

2020 ◽  
Vol 192 (12) ◽  
Author(s):  
Lorenzo D’Andrea ◽  
Aida Campos ◽  
Karim Erzini ◽  
Paulo Fonseca ◽  
Simone Franceschini ◽  
...  
Keyword(s):  
Management Strategies ◽  
Fishing Effort ◽  
Negative Effects ◽  
Web Based ◽  
Management Plans ◽  
By Catch ◽  
Selection Of Species ◽  
Areas Of Interest ◽  
Ecosystem Based Fisheries Management ◽  
Selection Of

AbstractCurrent fishing practices often do not allow adequate selection of species or sizes of fish, resulting in unwanted catches, subsequently discarded, with the consequent negative effects on both marine communities and fisheries profitability. The cross-analysis of density patches of potential unwanted catches and distribution of fishing effort can support the identification of spatial-temporal hot-spots in which the fishing pressure should be reduced to limit the amount of discards. The MinouwApp represents a technological and methodological framework to bring different, and structurally complex, sources of georeferenced data together into a simple visual interface aiming to interactively explore temporal ranges and areas of interest. The objective is to improve the understanding of fisheries dynamics, including discards, thus contributing to the implementation of discard management plans in a context of participative, ecosystem-based fisheries management strategies.

scholarly journals Mobulid rays feed on euphausiids in the Bohol Sea

2017 ◽  
Vol 4 (5) ◽  
pp. 161060 ◽  
Author(s):  
Christoph A. Rohner ◽  
Katherine B. Burgess ◽  
Joshua M. Rambahiniarison ◽  
Joshua D. Stewart ◽  
Alessandro Ponzo ◽  
...  
Keyword(s):  
Life History ◽  
Food Resource ◽  
Stomach Contents ◽  
Fishing Effort ◽  
Fishing Activity ◽  
Prey Preferences ◽  
Manta Birostris ◽  
History Of ◽  
By Catch ◽  
Mobula Japanica

Mobulid rays have a conservative life history and are caught in direct fisheries and as by-catch. Their subsequent vulnerability to overexploitation has recently been recognized, but fisheries management can be ineffective if it ignores habitat and prey preferences and other trophic interactions of the target species. Here, we assessed the feeding ecology of four mobulids ( Manta birostris , Mobula tarapacana , M. japanica , M. thurstoni ) in the Bohol Sea, Philippines, using stomach contents analysis of fisheries specimens landed between November and May in 2013–2015. We show that the mobulids feed heavily on euphausiid krill while they are in the area for approximately six months of the year. We found almost no trophic separation among the mobulid species, with Euphausia diomedeae as the major prey item for all species, recorded in 81 of 89 total stomachs (91%). Mobula japanica and M. thurstoni almost exclusively had this krill in their stomach, while M. tarapacana had a squid and fish, and Ma. birostris had myctophid fishes and copepods in their stomachs in addition to E. diomedeae . This krill was larger than prey for other planktivorous elasmobranchs elsewhere and contributed a mean of 61 364 kcal per stomach (±105 032 kcal s.e., range = 0–631 167 kcal). Our results show that vertically migrating mesopelagic species can be an important food resource for large filter feeders living in tropical seas with oligotrophic surface waters. Given the conservative life history of mobulid rays, the identification of common foraging grounds that overlap with fishing activity could be used to inform future fishing effort.

scholarly journals Age, growth, mortality and yield per recruit of the dourado Salminus brasiliensis, Corumbá Reservoir, Goiás State, Brazil

2009 ◽  
Vol 7 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Claudenice Dei Tos ◽  
Luiz Carlos Gomes ◽  
Angelo Antônio Agostinho ◽  
Rosana Paulo Batista
Keyword(s):  
Mortality Rate ◽  
Total Mortality ◽  
Fishing Effort ◽  
Average Weight ◽  
Migratory Species ◽  
Reservoir Impoundment ◽  
Annual Total ◽  
One Year ◽  
Yield Per Recruit ◽  
Salminus Brasiliensis

In order to evaluate the fate of the migratory species dourado Salminus brasiliensis in the first years of impoundment in Corumbá Reservoir we estimated age, growth, mortality and yield per recruit. Samplings were carried out monthly in Corumbá Reservoir and its main tributaries (Goiás State) from March 1998 to February 1999 using gillnets. After one year of impoundment, age was estimated from scales and the maximum number of rings was six for males and five for females. Rings are formed annually in May and June. The asymptotic length and growth rate for males and females were 37.1 cm and 0.77 and 56.6 cm and 0.52, respectively. A dominance of juveniles was verified in the reservoir and its tributaries. The instantaneous total mortality rate (Z) was 1.59 and the annual total mortality rate (A) was 79.6%. The highest yield per recruit (1200g) and the highest average weight (1900g) were obtained in simulations with low values of fishing (F) and natural (M) mortalities. Based on the above information we describe the Corumbá Reservoir impoundment has influenced the growth of the dourado. As regards this study, we recommend that the fishing effort not be applied during the trophic upsurge period and that the monitoring of the dourado assemblage continue. Fishery programs management for this species should be carried out with subsequent monitoring involving efficient communication, realistic practices and involvement of fisher organizations.

Problems and Perspectives Regarding Recruitment of Spiny Lobsters, Panulirus argus, to the South Florida Fishery

1986 ◽  
Vol 43 (11) ◽  
pp. 2099-2106 ◽  
Author(s):  
William G. Lyons
Keyword(s):  
Carapace Length ◽  
Spiny Lobster ◽  
Fishing Effort ◽  
International Management ◽  
South Florida ◽  
Panulirus Argus ◽  
Minimum Size ◽  
Juvenile Growth ◽  
Larval Recruitment ◽  
Yield Per Recruit

Inappropriate minimum size, illegal harvest, fishery-induced juvenile growth retardation and mortality, and excessive effort have reduced reproductive contributions and depressed yield-per-recruit in the overcapitalized south Florida spiny lobster (Panulirus argus) fishery. Measures recommended to improve yield-per-recruit are as follows: increase minimum legal size to 85–90 mm carapace length; require escape gaps in traps; eliminate possession of sublegal lobsters aboard vessels; prohibit harvest in nurseries; reduce fishing effort; improve enforcement of fishery regulations; and initiate programs to educate fishermen regarding impacts of fishery practices. International management is recommended to assure larval recruitment among Pan-Caribbean stocks.

Eggs-per-recruit model for management of the California market squid (Loligo opalescens) fishery

2005 ◽  
Vol 62 (7) ◽  
pp. 1640-1650 ◽  
Author(s):  
Michael R Maxwell ◽  
Larry D Jacobson ◽  
Ramon J Conser
Keyword(s):  
Mortality Rate ◽  
Egg Laying ◽  
Reference Points ◽  
Model Parameters ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Loligo Opalescens ◽  
Maturation Rate ◽  
Sampling Procedures ◽  
Yield Per Recruit

We develop a per-recruit model for the management of the California market squid (Loligo opalescens) fishery. Based on recent confirmation of determinate fecundity in this species, we describe how catch fecundity (i.e., eggs remaining in the reproductive tracts of harvested females) can be used to simultaneously infer fishing mortality rate along with management reference points such as yield-per-recruit, spawned eggs-per-recruit, and proportional egg escapement. Rates of mortality and egg laying have important effects on these reference points. Somewhat surprisingly, increasing the rate of natural mortality decreased spawned eggs-per-recruit while increasing proportional egg escapement. Increasing the rate of egg laying increased both spawned eggs-per-recruit and egg escapement. Other parameters, such as the maturation rate and gear vulnerability of immature females, affected the reference points. In actual practice, the influence of these parameters for immature squid may go undetected if immature squid are excluded from analysis of the catch. Application of this model to routine management is feasible but requires refinement of sampling procedures, biological assumptions, and model parameters. This model is useful because it is grounded on empirical data collected relatively inexpensively from catch samples (catch fecundity) while allowing for the simultaneous calculation of instantaneous fishing mortality rate and egg escapement.

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