Maximum sustainable yield with continuous age structure and density-dependent recruitment

1994 ◽  
Vol 120 (1) ◽  
pp. 99-126 ◽  
Author(s):  
Bernard Dacorogna ◽  
François Weissbaum ◽  
Roger Arditi
Keyword(s):  
Age Structure ◽  
Maximum Sustainable Yield ◽  
Sustainable Yield ◽  
Density Dependent

Spatial variation in fishing intensity and its effect on yield

2008 ◽  
Vol 65 (4) ◽  
pp. 588-599 ◽  
Author(s):  
Stephen Ralston ◽  
Michael R O’Farrell
Keyword(s):  
Spatial Variation ◽  
Local Density ◽  
Life Stage ◽  
Maximum Sustainable Yield ◽  
Recruitment Rate ◽  
Sustainable Yield ◽  
Fishing Mortality ◽  
Density Dependent ◽  
Age Structured ◽  
Effect On Yield

Fishing mortality is rarely, if ever, evenly distributed over space, yet this is a common assumption of many fisheries models. To evaluate the effect of spatial heterogeneity in fishing mortality on yield, we constructed age-structured models that allowed for differing levels of fishing in three regions within the boundaries of a stock and explored alternative assumptions about the life stage in which density-dependent compensation operates. If the fishing mortality rate (F) is not excessive (i.e., F ≤ FMSY defined for the spatially homogeneous case; MSY, maximum sustainable yield), simulations demonstrated that minor to moderate spatial variation in fishing intensity does not impact sustainable yield. However, if fishing mortality is excessive (F > FMSY), spatial variation in fishing intensity often improves yield and can actually produce yields in excess of MSY when compensation occurs after dispersal, and the density-dependent recruitment rate is a function of the local density of adults. The yield premium generated in these simulations by postdispersal density dependence is due to a low level of compensatory mortality in heavily fished areas coupled with dispersal of propagules into these areas from lightly fished adjacent regions.

scholarly journals Implications of late-in-life density-dependent growth for fishery size-at-entry leading to maximum sustainable yield

2018 ◽  
Vol 75 (4) ◽  
pp. 1296-1305 ◽  
Author(s):  
Rob van Gemert ◽  
Ken H Andersen
Keyword(s):  
Density Dependence ◽  
Maximum Sustainable Yield ◽  
Sustainable Yield ◽  
Fish Stocks ◽  
Density Dependent ◽  
Large Size ◽  
Adult Growth ◽  
Stock Assessments ◽  
Stock Recruitment ◽  
Dependent Growth

Abstract Currently applied fisheries models and stock assessments rely on the assumption that density-dependent regulation only affects processes early in life, as described by stock–recruitment relationships. However, many fish stocks also experience density-dependent processes late in life, such as density-dependent adult growth. Theoretical studies have found that, for stocks which experience strong late-in-life density dependence, maximum sustainable yield (MSY) is obtained with a small fishery size-at-entry that also targets juveniles. This goes against common fisheries advice, which dictates that primarily adults should be fished. This study aims to examine whether the strength of density-dependent growth in actual fish stocks is sufficiently strong to reduce optimal fishery size-at-entry to below size-at-maturity. A size-structured model is fitted to three stocks that have shown indications of late-in-life density-dependent growth: North Sea plaice (Pleuronectes platessa), Northeast Atlantic (NEA) mackerel (Scomber scombrus), and Baltic sprat (Sprattus sprattus balticus). For all stocks, the model predicts exploitation at MSY with a large size-at-entry into the fishery, indicating that late-in-life density dependence in fish stocks is generally not strong enough to warrant the targeting of juveniles. This result lends credibility to the practise of predominantly targeting adults in spite of the presence of late-in-life density-dependent growth.

scholarly journals Maximum sustainable yield, maximum economic yield and sustainability in fisheries

2020 ◽  
Vol 9 (1) ◽  
pp. 15-17
Author(s):  
Ernesto A Chávez
Keyword(s):  
Fisheries Management ◽  
Age Structure ◽  
Stock Assessment ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Fish Stock ◽  
Sustainable Yield ◽  
Fishing Mortality ◽  
Maximum Economic Yield ◽  
Fish Stock Assessment

A brief review of the concept of Maximum Sustainable Yield (MSY) used in fisheries management is discussed. The convenience of assessing the exploited stocks with the aid of simulation is advised, because implies the possibility to analyze the age structure of the fishery in more detail, as compared to the traditional methods of fish stock assessment. Emphasis is given to the use of the MSY as limit reference point because as long as the Fishing Mortality or fishing effort required for that point is kept at lower values, the fishery will have a good chance to be sustainable. A mention of the Maximum Economic Yield is made, proposing its use a target for the management, because it is reached in general with lower F values then that for the MSY, and this way keeping the fishery in a healthy condition.

MSY needs no epitaph—but it was abused

2020 ◽  
Author(s):  
Daniel Pauly ◽  
Rainer Froese
Keyword(s):  
Maximum Sustainable Yield ◽  
Sustainable Yield

Abstract The maximum sustainable yield (MSY) concept is widely considered to be outdated and misleading. In response, fisheries scientists have developed models that often diverge radically from the first operational version of the concept. We show that the original MSY concept was deeply rooted in ecology and that going back to that version would be beneficial for fisheries, not least because the various substitutes have not served us well.

Production, Mortality, And Sustainable Yield Of Northwest Atlantic Harp Seals (Pagophilus groenlandicus)

1978 ◽  
Vol 35 (9) ◽  
pp. 1249-1261 ◽  
Author(s):  
G. H. Winters
Keyword(s):  
Population Size ◽  
Total Population ◽  
Historical Data ◽  
Maximum Sustainable Yield ◽  
Sustainable Yield ◽  
Natural Mortality ◽  
Northwest Atlantic ◽  
The Past ◽  
Relative Contribution ◽  
Pagophilus Groenlandicus

From recent and historical data the natural mortality rate of adult harp seals (Pagophilus groenlandicus) is estimated to be 0.10 which is within the range of previous estimates (0.08–0.11). New estimates of bedlamer and 0-group natural mortality rates were not significantly different from those of adult seals. Pup production estimates from survival indices agreed well with those from sequential population analyses and indicated a decline from about 350 000 animals in the early 1950s to about 310 000 animals in the early 1970s. Over the same period the 1+ population size declined from 2.5 to 1.1 million animals but has been increasing at the rate of 3%/yr since the introduction of quotas in 1972. The relative contribution of the "Front" production to total ("Front" plus Gulf) production during the past decade has fluctuated from 49 to 87%, the average of 64% being very similar to the 61% obtained previously. These fluctuations suggest some interchange between "Front" and Gulf adults and it is concluded that homing in the breeding areas is a facultative rather than obligatory aspect of seal behavior. Thus the heavier exploitation of the "Front" production is probably sufficiently diffused into the total population to avoid serious effects on "Front" production. The maximum sustainable yield of Northwest Atlantic seals harvested according to recent patterns is estimated to be 290 000 animals (80% pups) from a 1+ population size of 1.8 million animals producing 460 000 pups annually. The sustainable yield at present levels of pup production (335 000 animals) is calculated to be 220 000 animals which is substantially above the present TAC of 180 000 animals and coincides with present harvesting strategies designed to enable the seal hunt to increase slowly towards the MSY level. Key words: mortality, production, sustainable yield, population dynamics, marine mammal

scholarly journals Can stock–recruitment points determine which spawning potential ratio is the best proxy for maximum sustainable yield reference points?

2013 ◽  
Vol 70 (6) ◽  
pp. 1075-1080 ◽  
Author(s):  
Christopher M. Legault ◽  
Elizabeth N. Brooks
Keyword(s):  
Life History ◽  
Mortality Rate ◽  
Maximum Sustainable Yield ◽  
Reference Points ◽  
Sustainable Yield ◽  
Marine Science ◽  
Fishing Mortality ◽  
Scatter Plots ◽  
Stock Recruitment ◽  
Spawning Potential Ratio

Abstract Legault, C. M., and Brooks, E. N. 2013. Can stock–recruitment points determine which spawning potential ratio is the best proxy for maximum sustainable yield reference points? – ICES Journal of Marine Science, 70: 1075–1080. The approach of examining scatter plots of stock–recruitment (S–R) estimates to determine appropriate spawning potential ratio (SPR)-based proxies for FMSY was investigated through simulation. As originally proposed, the approach assumed that points above a replacement line indicate year classes that produced a surplus of spawners, while points below that line failed to achieve replacement. In practice, this has been implemented by determining Fmed, the fishing mortality rate that produces a replacement line with 50% of the points above and 50% below the line. A new variation on this approach suggests FMSY proxies can be determined by examining the distribution of S–R points that are above or below replacement lines associated with specific SPRs. Through both analytical calculations and stochastic results, we demonstrate that this approach is fundamentally flawed and that in some cases the inference is diametrically opposed to the method's intended purpose. We reject this approach as a tool for determining FMSY proxies. We recommend that the current proxy of F40% be maintained as appropriate for a typical groundfish life history.

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