Modelling the effects of establishing a marine reserve for mobile fish species

2002 ◽  
Vol 59 (3) ◽  
pp. 405-415 ◽  
Author(s):  
P Apostolaki ◽  
E J Milner-Gulland ◽  
M K McAllister ◽  
G P Kirkwood
Keyword(s):  
Fish Species ◽  
Marine Reserve ◽  
High Mobility ◽  
Merluccius Merluccius ◽  
Seasonal Movements ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Short And Long Term ◽  
Immature Fish

We present a model of the effects of a marine reserve on spawning stock biomass (SSB) and short- and long-term yield for a size-structured species that exhibits seasonal movements. The model considers the effects of protecting nursery and (or) spawning grounds under a range of fishing mortalities and fish mobility rates. We consider two extremes of effort redistribution following reserve establishment and analyze the effects of a reserve when the fishery targets either mature or immature fish. We apply the model to the Mediterranean hake (Merluccius merluccius) and show that a marine reserve could be highly beneficial for this species. We demonstrate benefits from reserves not just for overexploited stocks of low-mobility species, but also (to a lesser extent) for underexploited stocks and high-mobility species. Greatly increased resilience to overfishing is also found in the majority of cases. We show that a reserve provides benefits additional to those obtained from simple effort control. Benefits from reserves depend to a major extent on the amount of effort redistribution following reserve establishment and on fishing selectivity; hence, these factors should be key components of any evaluation of reserve effectiveness.

Change in the rocky reef fish fauna of the iconic Poor Knights Islands Marine Reserve in north-eastern New Zealand over 4 decades

2018 ◽  
Vol 69 (10) ◽  
pp. 1496
Author(s):  
David R. Schiel ◽  
Tony Ayling ◽  
Michael J. Kingsford ◽  
Christopher N. Battershill ◽  
J. Howard Choat ◽  
...  
Keyword(s):  
Reef Fish ◽  
Fish Species ◽  
Marine Reserve ◽  
Fish Fauna ◽  
Rocky Reef ◽  
Long Term Effects ◽  
Before And After ◽  
Negative Effect ◽  
Reef Fish Species

Marine reserves exhibit increases in targeted fish species, but long-term effects on biodiversity are poorly understood. Factors other than reserve status may affect decadal changes, including environmental change. We examined the fish fauna at the iconic Poor Knights Islands over 4 decades (1974–2016) before and after implementation of a no-take marine reserve in 1998. We document a substantial increase in commercially and recreationally targeted Chrysophrys auratus, which was virtually absent before 1994 but by 2016 had reached up to 11 fish per 500m2 (220 per hectare). There were also large changes to the fish community, including the decline of subtropical and coastal wrasses, some species with no change and others that increased significantly. Many declines occurred >20 years before the arrival of abundant C. auratus, suggesting the changes do not represent a trophic cascade. Furthermore, this normally benthic-feeding fish has adopted a mid-water foraging behaviour targeting planktivorous fish. The increase in C. auratus appears to be linked both to reserve status and catch regulations in the wider region. Overall, the data point to long-term environmental fluctuations from the late 1970s having a negative effect on the abundance of more than half the reef fish species at these islands.

scholarly journals Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information

2009 ◽  
Vol 67 (2) ◽  
pp. 258-269 ◽  
Author(s):  
Ernesto Jardim ◽  
Santiago Cerviño ◽  
Manuela Azevedo
Keyword(s):  
Management Strategies ◽  
Maximum Sustainable Yield ◽  
Sustainable Yield ◽  
Fishing Mortality ◽  
Merluccius Merluccius ◽  
Total Allowable Catch ◽  
Recovery Plan ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The Impact

Abstract Jardim, E., Cerviño, S., and Azevedo, M. 2010. Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information. – ICES Journal of Marine Science, 67: 258–269. Iberian hake assessment revealed an increase in fishing mortality (F) despite enforcement of a recovery plan. Recent landings exceeded the total allowable catch and discarding rates were high. Alternative management strategies based on F control were evaluated with respect to the probability of recovering spawning-stock biomass (SSB), expected profits, and robustness to uncertainty on catch information and stock dynamics. Results showed that the use of censored catch data, i.e. excluding the Gulf of Cádiz or discards, may lead to inappropriate conclusions. Reducing fishing mortality was necessary for SSB to recover. An Fmax strategy with discard reduction showed the highest probability of rebuilding SSB and led the fishery to sustainable exploitation, with an expected %SPR of 30–40% in 2025, mean individual weight in the landings of 450 g in 2015, and yield increasing by >20%. Because of uncertainty in the estimates of maximum sustainable yield, management strategies based on FMSY were least robust, but all strategies were robust to alternative stock–recruit models.

Pronounced long-term juvenation in the spawning stock of Arcto-Norwegian cod (Gadus morhua) and possible consequences for recruitment

2008 ◽  
Vol 65 (3) ◽  
pp. 523-534 ◽  
Author(s):  
Geir Ottersen
Keyword(s):  
Time Series ◽  
Gadus Morhua ◽  
Experimental Studies ◽  
Reproductive Capacity ◽  
Fish Stocks ◽  
Stock Biomass ◽  
Clear Link ◽  
Spawning Stock ◽  
The Mean

The oldest and largest individuals are disappearing from many fish stocks worldwide as a result of overexploitation. This has been suggested to impair recruitment through decreasing the reproductive capacity of the spawners and increasing the mortality rate of the offspring. By using a time series on spawners biomass by age class for Arcto-Norwegian cod (Gadus morhua) from 1913–2004, I have documented pronounced changes in the spawning stock, including a trend towards younger fish, a less diverse distribution across ages, and a declining proportion of repeat spawners. Despite the total spawning stock biomass (SSB) being at similar levels now as in 1933, the mean age in the SSB has declined from 10–12.5 years to 7–8 years during the study period, and the percentage of fish of age 10 or above in the SSB has decreased from ~97% to ~10%. Contrary to earlier theoretical and experimental studies, no clear link between age structure and recruitment was found here. Recruitment to the Arcto-Norwegian cod stock may thus be more robust towards spawner juvenation than expected, possibly because of strong recruitment compensation.

scholarly journals AQUAM—A Decision Support Software for Fish Farm Management

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Marius Radulescu
Keyword(s):  
Decision Support ◽  
Fish Species ◽  
Fish Farm ◽  
Fish Growth ◽  
Fresh Water Fish ◽  
Fish Farms ◽  
Efficient Management ◽  
Short And Long Term ◽  
Support Software

In this paper, a software for management and decision support in a fish farm is presented. The software called AQUAM is dedicated to fresh water fish farms. Its aim is to make an efficient management of resources through planning, monitoring, analysis and decision support. Successful planning and management requires the integration of data related to ponds, fish species, fish growth, water and energy and economic analysis. AQUAM computes farm budgets relating various costs and returns in order to determine short and long term profitability. A simulation of the profit, as a function of the fish holding density, is performed with AQUAM. The data used in the simulation are from a fish farm of semi-intensive type, located in the region Danube Delta, at village Jurilovca, Tulcea county, Romania. The fish species that were taken into account were carp and sanger.

A length-based multispecies model for evaluating community responses to fishing

2006 ◽  
Vol 63 (6) ◽  
pp. 1344-1359 ◽  
Author(s):  
Stephen J Hall ◽  
Jeremy S Collie ◽  
Daniel E Duplisea ◽  
Simon Jennings ◽  
Mark Bravington ◽  
...  
Keyword(s):  
Fish Species ◽  
Single Species ◽  
Community Level ◽  
Fishing Mortality ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Multispecies Model ◽  
Species Declines ◽  
Ecosystem Based Fisheries Management ◽  
Biomass Spectra

Quantitative ecosystem indicators are needed to fulfill the mandate for ecosystem-based fisheries management. A variety of community metrics could potentially be used, but before reference levels for such indices can be established the sensitivity of candidate indices to fishing and other disturbances must be determined. One approach for obtaining such information is to test candidate indicators with models that mimic real ecosystems and can be manipulated experimentally. Here we construct a size-based multispecies model of a community of fish species that interact by predation. The model was parameterized for 21 fish species to obtain a predation-regulated community. Following an analysis of the sensitivity of the model to parameter uncertainty, we tested the sensitivity of community-level indicators to increasing levels of fishing mortality (F). Abundance and biomass spectra were sensitive to fishing mortality, with the slope decreasing with increasing F. Species diversity size spectra were also very sensitive to F, with diversity in the largest size classes declining rapidly. In contrast, k-dominance curves were less sensitive to fishing pressure. Importantly, however, although most community-level metrics showed clear trends in response to fishing, single-species declines in spawning stock biomass were the most sensitive indicators of fishing effects.

scholarly journals Multivariate determination of Atlantic herring population health in a large marine ecosystem

2019 ◽  
Vol 76 (4) ◽  
pp. 859-869
Author(s):  
Daniel G Boyce ◽  
Brian Petrie ◽  
Kenneth T Frank
Keyword(s):  
Population Health ◽  
Conservation Status ◽  
Marine Ecosystem ◽  
Rapid Decline ◽  
Average Weight ◽  
Atlantic Herring ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Large Marine Ecosystem

Abstract Atlantic herring are among the most harvested marine fish species globally and are of extraordinary ecological and economic importance. Within the Scotian Shelf and Bay of Fundy management zone (NAFO Division 4WX), herring support one of the largest fisheries in Canada, yet the conservation status of the stock is currently unclear. We use field observations, stock assessments, and published studies to evaluate the long-term (1965–2016) status, or health, of 4WX Atlantic herring based on 33 indicators that serve as proxies for the ecological dynamics across the larval, juvenile, and adult stages. Sixteen indicators that showed evidence of significant and synchronous temporal changes were integrated to produce a standardized series of herring population health. This multivariate index exhibited a gradual, long-term decline punctuated by a more rapid decline between 1980 and 2005. Following normalization, future trajectories of herring spawning stock biomass (SSB) over this period were best forecast by the average weight of herring (r2 = 0.63; lag = 6 years) and indicated that SSB would remain low over the next 6 years. Our study suggests that integrating factors related to population health can provide deeper insight in situations where individual series are uncertain and can complement existing assessment approaches.

scholarly journals Fishing for MSY: using “pretty good yield” ranges without impairing recruitment

2016 ◽  
Vol 74 (2) ◽  
pp. 525-534 ◽  
Author(s):  
Anna Rindorf ◽  
Massimiliano Cardinale ◽  
Samuel Shephard ◽  
José A. A. De Oliveira ◽  
Einar Hjorleifsson ◽  
...  
Keyword(s):  
Good Yield ◽  
Maximum Sustainable Yield ◽  
Fishing Mortality ◽  
Fish Yield ◽  
Fish Stocks ◽  
Northern European ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Average Catch

Pretty good yield (PGY) is a sustainable fish yield corresponding to obtaining no less than a specified large percentage of the maximum sustainable yield (MSY). We investigated 19 European fish stocks to test the hypothesis that the 95% PGY yield range is inherently precautionary with respect to impairing recruitment. An FMSY range was calculated for each stock as the range of fishing mortalities (F) that lead to an average catch of at least 95% of MSY in long-term simulations. Further, a precautionary reference point for each stock (FP.05) was defined as the F resulting in a 5% probability of the spawning-stock biomass falling below an agreed biomass limit below which recruitment is impaired (Blim) in long-term simulations. For the majority of the stocks analysed, the upper bound of the FMSY range exceeded the estimated FP.05. However, larger fish species had higher precautionary limits to fishing mortality, and species with larger asymptotic length were less likely to have FMSY ranges impairing recruitment. Our study shows that fishing at FMSY generally is precautionary with respect to impairing recruitment for highly exploited teleost species in northern European waters, whereas the upper part of the range providing 95% of MSY is not necessarily precautionary for small- and medium-sized teleosts.

scholarly journals Consequences of bias in age estimation on assessment of the northern stock of European hake (Merluccius merluccius) and on management advice

2007 ◽  
Vol 64 (5) ◽  
pp. 981-988 ◽  
Author(s):  
Michel Bertignac ◽  
Hélène de Pontual
Keyword(s):  
Age Estimation ◽  
Growth Parameters ◽  
Reference Points ◽  
Fishing Mortality ◽  
Merluccius Merluccius ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Management Advice ◽  
The Impact ◽  
European Hake

Abstract Bertignac, M., and de Pontual, H. 2007. Consequences of bias in age estimation on assessment of the northern stock of European hake (Merluccius merluccius) and on management advice. – ICES Journal of Marine Science, 64: 981–988. The results of a pilot tagging study on hake (Merluccius merluccius), conducted in the northern part of the Bay of Biscay in 2002, indicate that growth rates for this stock may be currently underestimated because of biased estimates of age. The impact that such a bias may have on the stock dynamics and the trends of the key population parameters, recruitment, spawning-stock biomass (SSB), and mortality are investigated. Assuming new growth parameters, a new age–length key is derived and used to produce and catch-at-age data and abundance indices, which are then used to assess the stock. Bias in estimating age affects the absolute levels of fishing mortality and stock biomass estimates, and also impacts the trend in SSB. However, trends in fishing mortality and recruitment are comparable, and the stock status with respect to precautionary reference points is broadly the same. As expected, the simulation also shows that the stock may be more reactive to changes in fishing levels, which affect medium-term forecasts. Long-term sustainable yields may also be impacted.

scholarly journals Population dynamics and stock assessment of grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-west coast of India

2017 ◽  
Vol 64 (3) ◽  
Author(s):  
G. B. Purushottama ◽  
Gyanaranjan Dash ◽  
Thakur Das ◽  
K. V. Akhilesh ◽  
Shoba Joe Kizhakudan ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Stock Assessment ◽  
Total Mortality ◽  
North West ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Yield Per Recruit ◽  
Peak Phase

The life history and exploitation parameters of Rhizoprionodon oligolinx Springer, 1964 were assessed using commercial landing data of 2012-2015 from Mumbai waters of India to understand the population dynamics and stock status of the species. The average annual landing of the species was estimated to be 383 t, which formed about 9.1% of the total shark landings of Maharashtra. L∞, K and t0 estimated were 97.1 cm, 0.47 yr-1 and -0.79 yr respectively. Total mortality (Z), fishing mortality (F) and natural mortality (M) rates were estimated as 2.16 yr-1, 1.48 yr-1 and 0.69 yr-1 respectively. The length at capture (L50), length at female maturity (Lm50) and male maturity (Lm50) were estimated as 49.7, 62.3 and 59.5 cm respectively, which indicated that most of the sharks entered peak phase of exploitation before attaining sexual maturity. Length-weight relationship indicated allometric growth (b>3) for the species. The species was found to be a continuous breeder and showed peak recruitment during April. The current exploitation rate (Ecur) was found to be 0.68, which is lower than Emax estimated for the species using Beverton and Holt yield per recruit analysis. Thompson and Bell prediction model showed that at current exploitation level, the biomass (B) has reduced to 32% of virgin biomass (B0) where as, the spawning stock biomass (SSB) has reduced to 16% of the virgin spawning stock biomass (SSB0). Hence the exploitation level for the species should be reduced by 40% that will ensure the availability of SSB at a relatively safer 30% level to rebuild the stock for long term sustainability of the resource.

scholarly journals AQUAM – A decision support software for fish farm management

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Marius Radulescu
Keyword(s):  
Decision Support ◽  
Fish Species ◽  
Fish Farm ◽  
Fish Growth ◽  
Fresh Water Fish ◽  
Fish Farms ◽  
Efficient Management ◽  
Short And Long Term ◽  
Support Software

In this paper a software for management and decision support in a fish farm is presented. The software called AQUAM is dedicated to fresh water fish farms. Its aim is to make an efficient management of resources through planning, monitoring, analysis and decision support. Successful planning and management requires the integration of data related to ponds, fish species, fish growth, water and energy and economic analysis.AQUAM computes farm budgets relating various costs and returns in order to determine short and long term profitability. A simulation of the profit, as a function of the fish holding density, is performed with AQUAM. The data used in the simulation are from a fish farm of semi-intensive type, located in the region Danube Delta, at village Jurilovca, Tulcea county, Romania. The fish species that were taken into account were carp and sanger.

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