The monitoring of biological effects: the separation of natural changes from those induced by pollution

1979 ◽  
Vol 286 (1015) ◽  
pp. 597-609 ◽  
Keyword(s):  
Biological Effects ◽  
Total Mortality ◽  
Fish Population ◽  
Maximum Sustainable Yield ◽  
The Self ◽  
Fish Populations ◽  
Sustainable Yield ◽  
Density Dependent Mortality ◽  
Unknown Risk ◽  
Dependent Mortality

An added mortality rate of eggs, larvae and juveniles of fish populations, or impact, is assumed to be density independent. The total mortality from hatching to recruitment is represented by the fecundity, and any increment in density independent mortality implies a decrement in density dependent mortality. At high stock the consequence is an increase in stock towards a position of less resilience: at low stock less resilience is found with a decrease in stock. In general impact generates a shift of K -strategy, the self-stabilizing strategy, to r -strategy, an opportunistic one. In a fish population very little impact should be tolerated at low stock because it would prevent recovery to a management objective such as maximum sustainable yield. At high stock, impact may generate more stock at an unknown risk.

Abundance, Growth, and Production Estimation of the Blue Mussel Mytilus edulis on Moored Navigation Buoys in the Estuary and Northwestern Gulf of St. Lawrence

1991 ◽  
Vol 48 (12) ◽  
pp. 2408-2419 ◽  
Author(s):  
P.-L. Ardisson ◽  
E. Bourget
Keyword(s):  
Mytilus Edulis ◽  
Blue Mussel ◽  
Initial Density ◽  
Maximum Size ◽  
The Self ◽  
Reference Region ◽  
Age Classes ◽  
Density Dependent Mortality ◽  
North Shore ◽  
Dependent Mortality

Production of Mytilus edulis was estimated from measurements of recruitment, growth, and abundances. The study is based on (1) yearly samplings carried out between 1975 and 1985 on 161 navigation buoys moored each year in the Estuary and Gulf of St. Lawrence and (2) monthly production estimates in a reference region in 1987. The relationships between production and maximum size, biomass, mean weight per individual, and abundance were calculated for this reference region. Maximum size and biomass were the parameters best reflecting production. Abundance and production estimates showed that the Gaspé Peninsula and the western North Shore zones were the most productive ones. The density-dependent mortality of individuals in crowded even-aged populations (self-thinning) was studied in the baie de Gaspé, the region showing the highest abundance and growth rate of Mytilus in the system. The slope of this relationship varied depending on initial density and age classes considered. These results, when compared with the theoretical value of the self-thinning model, suggest that the biomass observed on the buoys and the production estimates derived from them correspond to near-maximal values

scholarly journals Stock Assessment of Lates niloticus in Upper Victoria Nile and its Impact on Uganda’s Economy

2021 ◽  
Vol 19 (2) ◽  
pp. 11-26
Author(s):  
Samuel Bassa ◽  
Albert Getabu ◽  
Erick Ogello ◽  
Anthony Taabu Munyaho ◽  
Dickson Oteino Owiti ◽  
...  
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Sustainable Yield ◽  
Nile Perch ◽  
Lates Niloticus ◽  
Slot Size ◽  
Catch Rates ◽  
A Minor

This study investigated the growth, mortality, recruitment, and catch estimates of Nile perch, Lates niloticus (Linnaeus, 1758), in Upper Victoria Nile, basing on total catches and length-frequency data collected between 2008 and 2018. The asymptotic length (L∞) had a value of 93.45 cm TL, growth curvature (K) was 0.446 year-1, total mortality (Z) was 1.85year-1, natural mortality (M) was 0.79 year-1, fishing mortality (F) was 1.09 year-1, exploitation rate (E) was 0.59 and growth performance index(ᴓ) of (L∞) was 3.604. There were two peaks recruitment period, a minor one in March and a major one in August. These respectively accounted for 12.8 and 26.3 percent of the total catch. The optimum sustainable yield (E0.5), maximum sustainable yield (Emax) and, economic yield (E0.1) was 0.278, 0.421 and 0.355 respectively. The findings suggest that there is a decline in the population of Lates niloticus in Upper Victoria Nile. Therefore, strict management of the fishery by adhering to the recommended slot size of 50-85 cm TL and curtailing use of illegal gears is needed. This will be possible through enforcement of regulations, monitoring, control and surveillance in order to ensure sustainability of the Nile perch fishery and ecosystem restoration in the Upper VictoriaNile.Keywords: Lates niloticus; Catch rates; Growth parameters, Upper Victoria Nile.

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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