Maximum sustainable yield estimation of enhancement species with the characteristics of movement inside and outside marine ranching

Marine ranching can be regarded as a type of artificial fishery,and its construction aims at the sustainable utilisation of fishery resources.Therefore,the sustainable yield level of target species in marine ranching has become one of the concerns of stakeholders.The enhancement surplus production model proposed by Wang(2021)based on the traditional surplus production model can be used to assess the sustainable utilisation of settled species in marine ranches.However,when the target species has the characteristics of migration inside and outside marine ranches,its sustainability assessment will be aff ected.Based on the movement range and resource density levels of enhancement species inside and outside marine ranches,we built a biomass change model that is suitable for enhancement species with migration characteristics inside and outside marine ranches(migration enhancement biomass model).Moreover,we simulated the effects of factors,such as the ratio of the movement range and the ratio of resource density within and outside marine ranches and the fishing strategy for the enhancement species in marine ranches,on the estimation of maximum sustainable yield(MSY).Results show that the large movement range of enhancement species outside marine ranches was associated with the obvious advantage of the proposed migration enhancement model over the traditional enhancement production model.A small difference in the densities of enhancement species inside and outside marine ranches was highly beneficial for improving the accuracy of MSY estimation.The migration enhancement biomass model proposed in this study provides an idea for estimating the MSY of an enhancement species that migrates inside and outside marine ranches.Researchers can adjust the parameters of the model in accordance with the actual situation of resource distribution and changes to improve the scientificity of fishery stock assessment.

Applying the Catch-MSY model to the stock assessment of the northwestern Pacific saury Cololabis Saira

The Pacific saury(Cololabis saira)is one of the major harvested species in the temperate waters of the northwestern Pacific Ocean(NPO).The Catch-MSY model uses catch data and basic life history information to estimate the Maximum Sustainable Yield(MSY)for data-limited fisheries.Since there is considerable uncertainty in the current status of the Pacific saury stock in the NPO,the Catch-MSY model was used in this study to estimate MSY on the basis of catch data and life history information from the North Pacific Fisheries Commission(NPFC).During the process,17 scenarios,according to different prior distributions of the intrinsic rate of increase(r)and carrying capacity(K),were set for sensitivity analysis.Moreover,the influence of different catch time series and different process errors were taken into account.The results show the following:(1)there was a strong negative correlation relationship between ln(r)and ln(K);the MSY increases with an increase in the lower limit of r;(2)The time series of catch data had a limited impact on the assessment results,whereas the results of the model were sensitive to the annual catch in the first and last years;(3)The estimated MSYs of the Pacific saury were 47.37×10^4 t(41.57×10^4 t to 53.17×10^4 t)in scenario S1A and 47.53×10^4 t(41.79×10^4 t to 53.27×10^4 t)in scenario S1B.Given the uncertainty of the Catch-MSY model,maintaining a management target between 50×10^4 t and 70×10^4 t was a better management regulation.This study shows that the Catch-MSY model is a useful choice for estimating the MSY of data-limited species such as the Pacific saury.

Evaluation of the fishery status for King Soldier Bream Argyrops spinifer in Pakistan using the software CEDA and ASPIC

Catch and effort data were analyzed to estimate the maximum sustainable yield （MSY） of King Soldier Bream, Argyrops spinifer （Forsskal, 1775, Family： Sparidae）, and to evaluate the present status of the fish stocks exploited in Pakistani waters. The catch and effort data for the 25-years period 1985-2009 were analyzed using two computer software packages, CEDA （catch and effort data analysis） and ASPIC （a surplus production model incorporating covariates）. The maximum catch of 3 458 t was observed in 1988 and the minimum catch of 1 324 t in 2005, while the average annual catch ofA. spinifer over the 25 years was 2 500 t. The surplus production models of Fox, Schaefer, and Pella Tomlinson under three error assumptions of normal, log-normal and gamma are in the CEDA package and the two surplus models of Fox and logistic are in the ASPIC package. In CEDA, the MSY was estimated by applying the initial proportion （IP） of 0.8, because the starting catch was approximately 80% of the maximum catch. Except for gamma, because gamma showed maximization failures, the estimated results of MSY using CEDA with the Fox surplus production model and two error assumptions, were 1 692.08 t （R^2=0.572） and 1 694.09 t （R^2=0.606）, respectively, and from the Schaefer and the Pella Tomlinson models with two error assumptions were 2 390.95 t （R^2=0.563）, and 2 380.06 t （R^2=0.605）, respectively. The MSY estimated by the Fox model was conservatively compared to the Schaefer and Pella Tomlinson models. The MSY values from Schaefer and Pella Tomlinson models were the same. The computed values of MSY using the ASPIC computer software program with the two surplus production models of Fox and logistic were 1 498 t （R^2=0.917）, and 2 488 t （R^2=0.897） respectively. The estimated values of MSY using CEDA were about 1 700-2 400 t and the values from ASPIC were 1 500-2 500 t. The estimates output by the CEDA and the ASPIC packages indicate that the stock is overfished, and needs some effective management to reduce the fishing effort of the species in Pakistani waters.

Application of a Delay-Difference Model for the Stock Assessment of Southern Atlantic Albacore(Thunnus alalunga)

Delay-difference models are intermediate between simple surplus-production models and complicated age-structured models. Such intermediate models are more efficient and require less data than age-structured models. In this study, a delay-differ- ence model was applied to fit catch and catch per unit effort （CPUE） data （1975-2011） of the southern Atlantic albacore （Thunnus alalunga） stock. The proposed delay-difference model captures annual fluctuations in predicted CPUE data better than Fox model. In a Monte Carlo simulation, white noises （CVs） were superimposed on the observed CPUE data at four levels. Relative estimate error was then calculated to compare the estimated results with the true values of parameters a and fl in Ricker stock-recruitment model and the catchability coefficient q. a is more sensitive to CV than fl and q. We also calculated an 80% percentile confidence interval of the maximum sustainable yield （MSY, 21756 t to 23408 t; median 22490 t） with the delay-difference model. The yield of the southern Atlantic albacore stock in 2011 was 24122t, and the estimated ratios of catch against MSY for the past seven years were approxi- mately 1.0. We suggest that care should be taken to protect the albacore fishery in the southern Atlantic Ocean. The proposed de- lay-difference model provides a good fit to the data of southern Atlantic albacore stock and may be a useful choice for the assessment of regional albacore stock.

Application of a catch-based method for stock assessment of three important fisheries in the East China Sea

Most fisheries in China do not have maximum sustainable yield（MSY） estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch（TAC） for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model.Estimates for intrinsic rate of increase（r） and five levels of process error were considered. Results showed hairtail Trichiurus japonicas（Temminck and Schlegel） and small yellow croaker Larimichthys polyactis（Bleeker） fisheries experienced overfishing from the mid-1990 s to the early 2000 s, and the suggested TACs were 55.8×10^4 t and9.06×10^4 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea（Richardson） caused the fishery＇s collapse in the 1980 s, and it has not recovered until today.The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.

A continuous time delay-difference type model(CTDDM) applied to stock assessment of the southern Atlantic albacore Thunnus alalunga

A continuous time delay-difference model(CTDDM) has been established that considers continuous time delays of biological processes.The southern Atlantic albacore(Thunnus alalunga) stock is the one of the commercially important tuna population in the marine world.The age structured production model(ASPM) and the surplus production model(SPM) have already been used to assess the albacore stock.However,the ASPM requires detailed biological information and the SPM lacks the biological realism.In this study,we focus on applying a CTDDM to the southern Atlantic albacore(T.alalunga) species,which provides an alternative method to assess this fishery.It is the first time that CTDDM has been provided for assessing the Atlantic albacore(T.alalunga) fishery.CTDDM obtained the 80%confidence interval of MSY(maximum sustainable yield) of(21 510 t,23 118 t).The catch in 2011(24 100 t) is higher than the MSY values and the relative fishing mortality ratio(F_(2011)/F_(MSY)) is higher than 1.0.The results of CTDDM were analyzed to verify the proposed methodology and provide reference information for the sustainable management of the southern Atlantic albacore stock.The CTDDM treats the recruitment,the growth,and the mortality rates as all varying continuously over time and fills gaps between ASPM and SPM in this stock assessment.

Developing an intermediate-complexity projection model for China's fisheries:A case study of small yellow croaker(Larimichthys polyactis)in the Haizhou Bay,China

Projection models are commonly used to evaluate the impacts of fishing.However,previously developed projection tools were not suitable for China’s fisheries as they are either overly complex and data-demanding or too simple to reflect the realistic management measures.Herein,an intermediate-complexity projection model was developed that could adequately describe fish population dynamics and account for management measures including mesh size limits,summer closure,and spatial closure.A two-patch operating model was outlined for the projection model and applied to the heavily depleted but commercially important small yellow croaker(Larimichthys polyactis)fishery in the Haizhou Bay,China,as a case study.The model was calibrated to realistically capture the fisheries dynamics with hindcasting.Three simulation scenarios featuring different fishing intensities based on status quo and maximum sustainable yield(MSY)were proposed and evaluated with projections.Stochastic projections were additionally performed to investigate the influence of uncertainty associated with recruitment strengths and the implementation of control targets.It was found that fishing at FMSY level could effectively rebuild the depleted stock biomass,while the stock collapsed rapidly in the status quo scenario.Uncertainty in recruitment and implementation could result in variabilities in management effects;but they did not much alter the management effects of the FMSY scenario.These results indicate that the lack of science-based control targets in fishing mortality or catch limits has hindered the achievement of sustainable fisheries in China.Overall,the presented work highlights that the developed projection model can promote the understanding of the possible consequences of fishing under uncertainty and is applicable to other fisheries in China.

Catch per unit effort,maximum sustainable yield and exploitation of demersal fish of Omani artisanal fishery

Objective:To evaluate exploitation status of the stocks of demersal fishes in Omani artisanal fisheries.Methods:Time-series data between 2005 and 2014 on catches and effort represented by the number of fishing boats were used to estimate catch per unit effort and maximum sustainable yields applying Schaefer surplus production model.Regression analyses were made online using GraphPad software.Results:The study revealed that increasing the number of boats on the fishery caused a decrease of catch per unit effort of some species.Maximum sustainable yields and exploitation status were estimated for these species applying.Conclusions:Some demersal fish species were found to be caught in quantities exceeding maximum sustainable yields during some fishing seasons indicating overexploitation of their stocks.

Estimation of age and growth and mortality parameters of the sea cucumber Isostichopus fuscus (Ludwig, 1875) and implications for the management of its fishery in the Galapagos Marine Reserve

The fishery of the sea cucumber Isostichopus fuscus was the most important one in the early 2000s in the Galapagos Marine Reserve.Its overexploitation leads to its total closure from 2016 to 2021.At the end of this period,if the co-management system of the Galapagos Marine Reserve decides to open this fishery,a total allowed catch must be established using the methodology of Wolff,Schuhbauer,and Castrejón(2012).The objective of this paper is to evaluate this methodology and improve the total allowed catch calculation.We replicated Wolff et al.‘s methodology that uses the Cadima equation of Maximum Sustainable Yield(in Troadec,1977).We determined the age and growth parameters of I.fuscus to estimate total mortality and improved the calculation of the area of fishing and habitat of this species in Galapagos to estimate its abundance.We found inconsistences in Wolff et al.‘s estimations of mortality and abundance and we recommend that the Maximum Sustainable Yield be used not as the total allowed catch,but as a limit reference point for this fishery.We propose,instead,to use a dynamic abundance model that is capable of estimating a variety of reference points,including the fishing mortality for optimal fishing that is recommended to use to establish a total allowed catch.In addition,for the first time,the age and growth parameters of I.fuscus for Galapagos and the eastern-central region of the Pacific Ocean are determined(L∞=42.5 cm;K=0.21/year).