scholarly journals Analysis of the corvina gulf fishery as a function of management actions in the Upper Gulf of California, Mexico

2017 ◽  
Vol 41 (3) ◽  
pp. 498-505
Author(s):  
Joaquín Humberto Ruelas-Peña ◽  
Carmen Valdez-Muñoz ◽  
Eugenio Alberto Aragón-Noriega
Keyword(s):  
Gulf Of California ◽  
Stock Assessment ◽  
Biosphere Reserve ◽  
Information Criterion ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Optimum Level ◽  
Fishing Mortality ◽  
Commercial Catch ◽  
Management Actions

The gulf corvina (Cynoscion othonopterus), is an endemic species of the Gulf of California, and its fishery is one of the most important in the Upper Gulf of California. Two dynamic biomass models (Schaefer & Pella-Tomlinson), were used to assess the state of the stock due to the lack of enough age data for a reliable full age-structured stock assessment. The models required an historical annual time-series of the abundance index (from 1993 to 2010), derived from the commercial catch and effort data. The Akaike information criterion indicates that the best model was the Schaefer model. The maximum sustainable yield (MSY), estimated with the Schaefer model was 3.100 ton, with a maximum surplus biomass (BMSY) that will allow the capture of 8.200 ton, and a fishing effort (fMSY) of 457 boats. The fishing mortality (F = 0.43) was 26% higher than the fishing mortality at the biological reference point (F0.1 = 0.34). The average biomass from 2006 to 2010 was 52% of the optimum level of the fishery (Est2006-2010 < 1). In 1999 an increase of the fishing effort accelerated the decrease of the biomass. These results indicate that the stock has not been healthy, in spite of the Biosphere Reserve decree, because the core zone has not been respected as a prohibited zone for fishing, and because of the increased fishing effort. 

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.

scholarly journals Stock assessment and fishery management of the pink shrimp Farfantepenaeus brasiliensis Latreille, 1970 and F. paulensis Pérez-Farfante, 1967 in Southeastern Brazil (23° to 28° S)

2006 ◽  
Vol 66 (1b) ◽  
pp. 263-277 ◽  
Author(s):  
N. O. Leite Jr. ◽  
M. Petrere Jr.
Keyword(s):  
Fishery Management ◽  
Stock Assessment ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Southeastern Brazil ◽  
Pink Shrimp ◽  
Shrimp Fishery ◽  
Management Actions ◽  
Farfantepenaeus Paulensis ◽  
Using Data

Quantitative analyses of the pink shrimp (Farfantepenaeus brasiliensis and Farfantepenaeus paulensis) fisheries were carried out using data collected from July 1999 to July 2001 from the trawling operations of the fishing fleet based in Santos/Guarujá, SP. According to classical models, the fishery is at its maximum sustainable yield. Therefore, reduction of the fishing effort and adequate season and area closures seem to be the best management actions for the pink shrimp fishery.

Population dynamics and stock assessment of Hilsa shad, Tenualosa ilisha (Hamilton, 1822) along the coast of Bangladesh

2021 ◽  
Vol 48 (2) ◽  
pp. 231-241
Author(s):  
Md Khairul Islam ◽  
Md Humayun ◽  
Manmatha Nath Sarker ◽  
Md Sharifuddin ◽  
M Niamul Naser
Keyword(s):  
Growth Parameters ◽  
Stock Assessment ◽  
Population Analysis ◽  
Total Mortality ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Recruitment Pattern ◽  
Weight Relationship ◽  
Tenualosa Ilisha ◽  
Highly Correlated

Stock Assessment of Tenualosa ilisha (Hamilton, 1822) were estimated using FiSAT-II software with length-frequency data collected from different landing centers. The Southeast Coast of Bay Of Bengal, Cox's Bazar. The Von Bertalanffy growth parameters Land K for the species were asymptotic length (L∞) was 51.41 cm, growth rate (K) was 0.75 year-1 and t0 = -0.2 year respectively. The estimated value of total mortality (Z) based on length converted catch curve using these growth parameters was 2.35 year-1.Natural mortality (M) based on growth parameters and mean environmental temperature (T = 27° C) was 1.00 year-1 and fishing mortality (F) was 1.35 year-1. Optimum length of hilsa at first capture (Lc=L50) was 28.36 cm TL. Growth performance indices (ϕ') was 3.30. The estimated value of the exploitation rate (E) using the length-converted catch curve was 0.57. The recruitment pattern of this species was continuous and two peaks per year. The present investigation clearly showed the over fishing (E > 0.50) condition for T. ilisha in Bangladesh. The estimated length-weight relationship for the combined sex was found to be W = 0.0109 L3. Virtual population analysis (VPA) showed that the maximum fishing mortality occurring in the length between 30 to 35 cm with a maximum value in the length of 32 cm that repeatedly indicate high fishing mortality in the T. ilisha. The generalized length-weight relationship was fitted with the pooled data of all monthly samples were BW = 0.029 TL2.718 (R2= 0.833) respectively. The results revealed that all length-weight relationships were highly correlated (r > 0.993). Maximum sustainable yield (MSY) was estimated as 435,554 t. Bangladesh J. Zool. 48(2): 231-241, 2020

scholarly journals Managing fisheries in a world with more sea turtles

2020 ◽  
Vol 287 (1930) ◽  
pp. 20200220
Author(s):  
Nathan F. Putman ◽  
Jesse Hawkins ◽  
Benny J. Gallaway
Keyword(s):  
Stock Assessment ◽  
Sea Turtles ◽  
Sea Turtle ◽  
Fishing Effort ◽  
Eastern United States ◽  
Green Turtles ◽  
Management Actions ◽  
Nesting Sites ◽  
Near Shore ◽  
Turtle Population

For decades, fisheries have been managed to limit the accidental capture of vulnerable species and many of these populations are now rebounding. While encouraging from a conservation perspective, as populations of protected species increase so will bycatch, triggering management actions that limit fishing. Here, we show that despite extensive regulations to limit sea turtle bycatch in a coastal gillnet fishery on the eastern United States, the catch per trip of Kemp's ridley has increased by more than 300% and green turtles by more than 650% (2001–2016). These bycatch rates closely track regional indices of turtle abundance, which are a function of increased reproductive output at distant nesting sites and the oceanic dispersal of juveniles to near shore habitats. The regulations imposed to help protect turtles have decreased fishing effort and harvest by more than 50%. Given uncertainty in the population status of sea turtles, however, simply removing protections is unwarranted. Stock-assessment models for sea turtles must be developed to determine what level of mortality can be sustained while balancing continued turtle population growth and fishing opportunity. Implementation of management targets should involve federal and state managers partnering with specific fisheries to develop bycatch reduction plans that are proportional to their impact on turtles.

scholarly journals Probability of stochastic depletion: an easily interpreted diagnostic for stock assessment modelling and fisheries management

2014 ◽  
Vol 72 (2) ◽  
pp. 428-435 ◽  
Author(s):  
James T. Thorson ◽  
Olaf P. Jensen ◽  
Ray Hilborn
Keyword(s):  
Stock Assessment ◽  
Biological Effects ◽  
Decision Support Tool ◽  
Maximum Sustainable Yield ◽  
Support Tool ◽  
Management Actions ◽  
Stock Assessments ◽  
Harvest Control Rule ◽  
Recruitment Variability ◽  
Spawning Biomass

Abstract Marine fish populations have high variation in cohort strength, and the production of juveniles (recruitment) may have persistent positive or negative residuals (autocorrelation) after accounting for spawning biomass. Autocorrelated recruitment will occur whenever average recruitment levels change between oceanographic regimes or due to predator release, but may also indicate persistent environmental and biological effects on shorter time-scales. Here, we use estimates of recruitment variability and autocorrelation to simulate the stationary distribution of spawning biomass for 100 real-world stocks when unfished, fished at FMSY, or fished following a harvest control rule where fishing mortality decreases as a function of spawning biomass. Results show that unfished stocks have spawning biomass (SB) below its deterministic equilibrium value (SB0) 58% of the time, and below 0.5SB0 5% of the time on average across all stocks. Similarly, stocks fished at the level producing deterministic maximum sustainable yield (FMSY) are below its deterministic prediction of spawning biomass (SBMSY) 60% of the time and below 0.5SBMSY 8% of the time. These probabilities are greater for stocks with high recruitment variability, positive autocorrelation, and high natural mortality—traits that are particularly associated with clupeids and scombrids. An elevated probability of stochastic depletion, i.e. biomass below the deterministic equilibrium expectation, implies that management actions required when biomass drops below a threshold may be triggered more frequently than expected. Therefore, we conclude by suggesting that fisheries scientists routinely calculate these probabilities during stock assessments as a decision support tool for fisheries managers.

scholarly journals An investigation into fisheries interaction effects using Atlantis

2014 ◽  
Vol 72 (1) ◽  
pp. 275-283 ◽  
Author(s):  
Michael D. Smith ◽  
Elizabeth A. Fulton ◽  
Robert W. Day
Keyword(s):  
Fisheries Management ◽  
Carrying Capacity ◽  
Stock Assessment ◽  
Single Species ◽  
Interaction Effects ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Simultaneous Increase ◽  
Total Catch ◽  
The Impact

Abstract Fisheries management is commonly based on the outputs of single-species stock assessment models. While such models are appropriate for tactical issues such as quota setting, they typically omit explicit trophic interactions between different parts of the ecosystem. To successfully manage multiple fisheries in the same ecosystem, we need to understand how fishing one species may indirectly affect other species. In this paper, we used a simulation model of the southern Benguela ecosystem, built in the Atlantis framework, to explore fisheries interaction effects. We first measured the impact of fishing different stocks individually at FMSY, the hypothetical level of fishing effort which produces maximum sustainable yield (MSY) in a single-species modelling context. We then applied FMSY to all stocks simultaneously and compared the simultaneous yield with the sum of yields from the individual applications of FMSY. Contrary to expectations, the total catch was higher under the simultaneous scenario. We explored our results by studying the influences of trophic interaction between species at different levels of the foodweb, and found that our overall result was driven by two key factors: volumetric dominance of small pelagic fish in the total catch, and asymmetric influences of competition and predation between piscivorous and planktivorous species. The simultaneous increase in fishing pressure across multiple species in the model led to increased effective carrying capacity for small pelagic species (due to reduced competition), but reduced carrying capacity for piscivorous species (due to reduced small pelagic prey). This work has important implications for the design of tactical multispecies models for use in ecosystem-based fisheries management.

Setting biological reference points for sea scallops (Placopecten magellanicus) allowing for the spatial distribution of productivity and fishing effort

2017 ◽  
Vol 74 (5) ◽  
pp. 650-667 ◽  
Author(s):  
Stephen J. Smith ◽  
Jessica A. Sameoto ◽  
Craig J. Brown
Keyword(s):  
Spatial Distribution ◽  
Habitat Suitability ◽  
Spatial Model ◽  
Stock Assessment ◽  
Fishing Effort ◽  
Reference Points ◽  
Assessment Model ◽  
Fishing Mortality ◽  
Placopecten Magellanicus ◽  
Fishing Vessels

Management for the major sea scallop (Placopecten magellanicus) fisheries in Canada is based on maximum sustainable yield (MSY) biomass and fishing mortality reference points applied to the whole stock, under the assumption that fishing mortality is uniformly distributed in space. However, scallop fishing vessels concentrate fishing in areas that consistently exhibit high densities resulting in a nonuniform spatial distribution of fishing effort. This study applies a spatial model for fishing effort derived from satellite vessel monitoring system data, scallop habitat suitability maps, and relative scallop density from a spatial stock assessment model to evaluate precautionary approach reference points in support of sustainable management. Target harvest rates were evaluated in terms of MSY for the higher habitat suitability areas. The results indicated that although MSY for the spatial model were similar to those when assuming a uniform distribution of effort, the biomass and catch rates over all areas were higher. The spatial model predicted that the MSY would be taken with less fishing effort, potentially lessening the benthic impacts from the scallop fishery.

scholarly journals POTENTIAL PRODUCTION OF DEMERSAL FISH STOCK IN THE MALACCA STRAIT OF INDONESIA

2015 ◽  
Vol 21 (1) ◽  
pp. 45 ◽  
Author(s):  
Purwanto Purwanto
Keyword(s):  
Demersal Fish ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Fish Stock ◽  
Sustainable Yield ◽  
Optimum Level ◽  
Fish Production ◽  
Potential Production ◽  
Malacca Strait

Malacca Strait is one of the main fishing areas for demersal fishery in Indonesia. To support the management of that fishery, an assessment of the demersal fish stock was conducted. This study estimated that the maximum sustainable yield and the optimal catch per unit effortof demersal fishery in the Malacca Strait were about 106.8 thousand tons/year and 28.5 tons per unit of Danish seine, respectively, resulting from the operation of 3,752 Danish seines. Unfortunately, fishing effort was higher than its optimum level and the fish stock was over-exploited since 2003. To recover the demersal fish stock to its optimum level and to ensure the optimal fish production from demersal fishery in the Malacca Strait, it was necessary to reduce fishing effort at about 67% from its level in 2011.

scholarly journals Stock Reduction Analysis of Bigeye Croaker Micropogonias megalops in the Upper Gulf of California, Mexico

Fishes ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 15
Author(s):  
Ricardo Urías-Sotomayor ◽  
Guillermo Rodríguez-Domínguez ◽  
José Adán Félix-Ortiz ◽  
Gilberto G. Ortega-Lizárraga ◽  
Horacio A. Muñoz-Rubí ◽  
...  
Keyword(s):  
Model Selection ◽  
Gulf Of California ◽  
Selection Procedure ◽  
Fishing Effort ◽  
Free Access ◽  
Commercial Catch ◽  
Probable Function ◽  
Viable Solution ◽  
Stock Biomass ◽  
The One

A stock reduction analysis (SRA) of bigeye croaker Micropogonias megalops was performed based on commercial catch data. SRA solutions were restricted to a 2011 bigeye croaker stock biomass estimate of 14,412 t. The viable solution indicated a reduction in stock of 73.6% from 1983 to 2020 with an initial biomass of 22,186 t. In addition, a possible effect of hyperstability of the stock was evaluated by applying different versions of the Cobb–Douglas catch function. The most probable function based on a multi-model selection procedure was the one wherein the catch does not depend on biomass and is directly proportional to the applied fishing effort of small boats (~7 m) and vessels (~24 m). This situation suggests that in a free access regime, fishing can deplete the resource until it collapses, without observing a significant reduction in its catches until the event is very close.

scholarly journals Precisely wrong or vaguely right: simulations of noisy discard data and trends in fishing effort being included in the stock assessment of North Sea plaice

2007 ◽  
Vol 64 (9) ◽  
pp. 1641-1649 ◽  
Author(s):  
Mark Dickey-Collas ◽  
Martin A. Pastoors ◽  
Olvin A. van Keeken
Keyword(s):  
North Sea ◽  
Recent Trend ◽  
Stock Assessment ◽  
Target Population ◽  
Fishing Effort ◽  
Fishing Mortality ◽  
Recent Past ◽  
Clear Trend ◽  
The Past ◽  
Stock Assessments

Abstract Dickey-Collas, M., Pastoors, M. A, and van Keeken, O. A. 2007. Precisely wrong or vaguely right: simulations of noisy discard data and trends in fishing effort being included in the stock assessment of North Sea plaice. – ICES Journal of Marine Science, 64: 000–000. ICES stock assessments of North Sea plaice are routinely carried out with eXtended Survivors Analysis (XSA), based on landings and survey data. Recently, the assessments included data on discarded young fish, sampled with high variance. Fishing effort has been declining since the mid-1990s, so conditioning the estimated fishing mortality (F) on the recent past could introduce bias into the perceived stock size. Simulated populations with North Sea plaice-like characteristics are used to explore the dependence of the perceived stock dynamics on the inclusion of discards data at different sampling noise, using the same methods and XSA settings as ICES. The sensitivities of the results were tested against different trends in fishing effort and recruitment, and different scenarios for “shrinkage” (i.e. the way in which the past is used to estimate the most recent fishing mortality). Within the bounds of the simulation assumptions, the perception of population trends from an XSA stock assessment can be biased when there are trends in fishing effort: decreasing effort leads to underestimating SSB and overestimating F. When discards are not included, bias in SSB is greatest when effort decreases, and bias in F is greatest when effort increases. Bias in SSB and F were removed by including discard data, but at substantial loss of precision. If effort shows a clear trend and discards are substantial and estimated noisily, the recent trend in the target population may be hard to track with an XSA-type assessment methodology.

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