Island in the Stream: Oceanography and Fisheries of the Charleston Bump

2001 ◽  
Keyword(s):  
North Atlantic ◽  
Fishery Management ◽  
Population Analysis ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Stock Biomass ◽  
The Status ◽  
Eastern North Atlantic ◽  
Charleston Bump ◽  
Definition Of

<em> Abstract.</em>—The status of the wreckfish <em> Polyprion americanus </em>stock caught on the Blake Plateau in the southeastern United States Atlantic was analyzed by calibrated virtual population analysis (VPA) to estimate trends in fishing mortality and population (or stock) biomass. Calibration of the FADAPT VPA program was to fishery-dependent catch-per-unit effort (CPUE) for a range in assumed values for natural mortality (M). Age-length keys were developed from two aging studies of wreckfish (1988– 1992 and 1995–1998). Keys were developed annually (pooled across seasons to create three “annual” age-length keys to represent 1988–1990, 1991–1993, and 1994–1998) and seasonally (pooled across years to create three seasonal age-length keys to represent April–June, July–September, and October to end of fishing year on 15 January). Analyses based on both annual and seasonal catch matrices showed similar patterns and values, with the seasonal catch matrix producing slightly lower estimates of fishing mortality rates (F) and higher estimates of biological reference points based on F. Fishing mortality rates peaked in 1989, as did the maximum annual U.S. landings (4.2 million pounds). Subsequently, both landings and fishing mortality rates have generally declined. Although stock biomass has generally declined over the study period, recruitment at age 7 has risen since about 1994. Meanwhile, annual estimates of static spawning potential ratio (SPR), which are inversely related to F, have risen since 1994. Fishing mortality rates from recent low landings are at or near the South Atlantic Fishery Management Council’s threshold definition of overfishing (static SPR of 30%), while the process of rebuilding with improving recruitment appears to be underway. Concern persists because the assessment is based on the underlying assumption that wreckfish from the Blake Plateau form a single stock separate from the eastern North Atlantic and genetic evidence suggests the stock encompasses the entire North Atlantic.

Sustainability assessment for fishing effects (SAFE) on highly diverse and data-limited fish bycatch in a tropical prawn trawl fishery

2009 ◽  
Vol 60 (6) ◽  
pp. 563 ◽  
Author(s):  
Shijie Zhou ◽  
Shane P. Griffiths ◽  
Margaret Miller
Keyword(s):  
Mortality Rate ◽  
Fishery Management ◽  
Sustainability Assessment ◽  
Cost Effective ◽  
Mortality Rates ◽  
Assessment Method ◽  
Reference Points ◽  
Fishing Mortality ◽  
Point Estimates ◽  
Large Numbers

A new sustainability assessment for fishing effects (SAFE) method was used to assess the biological sustainability of 456 teleost bycatch species in Australia’s Northern Prawn Fishery. This method can quantify the effects of fishing on sustainability for large numbers of species with limited data. The fishing mortality rate of each species based on its spatial distribution (estimated from detection/non-detection data) and the catch rate based on fishery-dependent or fishery-independent data were estimated. The sustainability of each species was assessed by two biological reference points approximated from life-history parameters. The point estimates indicated that only two species (but 21 when uncertainty was included) had estimated fishing mortality rates greater than a fishing mortality rate corresponding to the maximum sustainable yield. These two species also had their upper 95% confidence intervals (but not their point estimates) greater than their minimum unsustainable fishing mortality rates. The fact that large numbers of species are sustainable can be attributed mainly to their wide distributions in unfished areas, low catch rates within fished areas and short life spans (high biological productivity). The present study demonstrates how SAFE may be a cost-effective quantitative assessment method to support ecosystem-based fishery management.

Incorporating Uncertainty into Fishery Models

2002 ◽  
Keyword(s):  
Fishery Management ◽  
Population Analysis ◽  
Management Plan ◽  
Atlantic Menhaden ◽  
Production Model ◽  
Fishing Mortality ◽  
Juvenile Abundance ◽  
Stock Assessments ◽  
Mortality Projections ◽  
Production Modeling

<em>Abstract.—</em>Stock assessments of Atlantic menhaden are conducted annually for the Atlantic States Marine Fisheries Commission, as required by the recently updated Fishery Management Plan, adopted in 1992. Uncertainties in stock assessments have been explored over the years from many perspectives. Two general areas of analysis are considered here. The first area is largely deterministic and concerns the virtual population analysis (VPA), including development and coherence of the catch-at-age matrix; historical retrospective problems; implications of assuming constant <EM>M </EM>at all ages analyzed; and reliability of recruitment estimates relative to fishery-independent juvenile abundance indices when used for calibrating the VPA. The second area of consideration comprises stochastic analyses, including stochastic projections based on biological benchmarks determined from yield-per-recruit and spawning-stockbiomass- per-recruit models; bootstrapped application of a surplus-production model; and projections from that production model. Nonetheless, the largest uncertainty in assessment of the stock stems not from modeling considerations, but is a biological question: Can the high stock levels observed in the 1950s be regained by reducing fishing mortality? Projections based on production modeling assume that they can, but if exogenous forces (for example, habitat loss or pollution) have affected the stock, it may be that they cannot. If the recent pattern of lower fishing mortality rates in response to social and economic factors continues, the fishery will in essence conduct an experiment that may answer the question.

Incorporating Uncertainty into Fishery Models

2002 ◽  
Keyword(s):  
Mortality Rate ◽  
Blue Crab ◽  
Stock Assessment ◽  
Probability Distributions ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Statistical Hypothesis Testing ◽  
Control Laws ◽  
Decision Confidence ◽  
The Status

<em>Abstract.—</em>Stock assessment methodology has increasingly employed statistical procedures as a means to incorporate uncertainty into assessment advice. Deterministic values of fishing mortality rates (<em>F<sub>t </sub></em>) estimated from assessment models have been replaced by empirical distributions that can be compared with an appropriate biological reference point (<em>F</em><sub>BRP</sub>) to generate statements of probability (e.g., Pr[<em>F<sub>t </sub></em>≥ <em>F</em><sub>BRP</sub>]) regarding the status of the resource. It must be recognized, however, that terminal year fishing mortality rates and the biological reference points to which they are compared are both estimated with error, which will impact the quality of decisions regarding the status of the stock. We propose a two-tier stochastic decision-based framework for a recently conducted stock assessment of the Delaware Bay blue crab stock that specifies not only the probability for the condition Pr(<em>F<sub>t </sub></em>≥ <em>F</em><sub>BRP</sub>), but also the statistical level of confidence (i.e., 90%) in that decision. The approach uses a mixed Monte Carlobootstrap procedure to estimate probability distributions for both the terminal year fishing mortality rate (<em>F<sub>t </sub></em>) and the replacement fishing mortality rate, approximated by <em>F</em><sub>MED</sub> as an overfishing definition. Probability density functions (PDFs) for <em>F<sub>t </sub></em>and <em>F</em><sub>MED</sub>, generated using the mixed Monte Carlo-bootstrap procedure, show that recent fishing mortality rates (80% CI from 0.6 to 1.2) are generally below the <em>F</em><sub>MED</sub> overfishing definition (80% CI from 0.9 to 1.6), with significant overlap in the PDFs. Using the PDFs, the stochastic decision-based approach then generates a probability profile by integrating the area under the <em>F<sub>t </sub></em>PDF for different decision confidence levels (e.g. 90%, 80%, 70%, etc.), which can be thought of as one-tailed <em>α</em>-probability from standard statistical hypothesis testing. For example, at the 80% decision confidence level (value of <em>F </em>corresponding to the upper 20% of the <em>F</em><sub>MED</sub> PDF), Pr(<em>F<sub>t </sub>> F</em>MED) is about 0.03. Thus, with high confidence (80%), we can state that the blue crab stock is not currently being overfished. This approach can be extended to decisions regarding control laws that specify both maximum fishing rate and minimum biomass thresholds.

Comparative performance of data-poor CMSY and data-moderate SPiCT stock assessment methods when applied to data-rich, real-world stocks

2020 ◽  
Author(s):  
Paul Bouch ◽  
Cóilín Minto ◽  
Dave G Reid
Keyword(s):  
Stock Assessment ◽  
Assessment Methods ◽  
Production Model ◽  
Fishing Mortality ◽  
Comparative Performance ◽  
Fish Stocks ◽  
Surplus Production ◽  
Stock Biomass ◽  
Surplus Production Model ◽  
The Status

Abstract All fish stocks should be managed sustainably, yet for the majority of stocks, data are often limited and different stock assessment methods are required. Two popular and widely used methods are Catch-MSY (CMSY) and Surplus Production Model in Continuous Time (SPiCT). We apply these methods to 17 data-rich stocks and compare the status estimates to the accepted International Council for the Exploration of the Sea (ICES) age-based assessments. Comparison statistics and receiver operator analysis showed that both methods often differed considerably from the ICES assessment, with CMSY showing a tendency to overestimate relative fishing mortality and underestimate relative stock biomass, whilst SPiCT showed the opposite. CMSY assessments were poor when the default depletion prior ranges differed from the ICES assessments, particularly towards the end of the time series, where some stocks showed signs of recovery. SPiCT assessments showed better correlation with the ICES assessment but often failed to correctly estimate the scale of either F/FMSY of B/BMSY, with the indices lacking the contrast to be informative about catchability and either the intrinsic growth rate or carrying capacity. Results highlight the importance of understanding model tendencies relative to data-rich approaches and warrant caution when adopting these models.

Evaluation of effort reduction in the Florida Keys spiny lobster, Panulirus argus, fishery using an age-structured population analysis

1997 ◽  
Vol 48 (8) ◽  
pp. 1045 ◽  
Author(s):  
Robert G. Muller ◽  
John H. Hunt ◽  
Thomas R. Matthews ◽  
William C. Sharp
Keyword(s):  
Fishery Management ◽  
Population Analysis ◽  
Spiny Lobster ◽  
Florida Keys ◽  
Environmental Damage ◽  
Population Fluctuations ◽  
Fishing Mortality ◽  
Time Period ◽  
Effort Reduction ◽  
Age Structured

A management programme implemented in Florida in 1993 was designed to reduce the number of traps in the spiny lobster fishery in order to reduce gear conflicts, environmental damage and effort without reducing harvest. Traps in the commercial fishery were reduced from 939 000 in 1991 to 568 000 in 1995. Landings by fishing season, zone (upper Florida Keys and lower Florida Keys), sex, and time period (summer v. winter) were pro-rated into numbers by length that were assigned ages by using growth simulations. From tag–recapture data, moult interval was estimated by using a logistic regression with terms for zone, sex, time period, carapace length, and time at large. For lobsters that moulted, the moult increment was modelled with a multiple regression including the same terms. Standardized catch-per-trip and total landings increased as traps were reduced. Age-structured analysis of the catches-at-age indicated that fishing mortality decreased by 16%, even as landings increased. It is not known whether the increase in landings was due to natural population fluctuations or to positive results of trap reduction. Fishing mortality rates still exceed common benchmarks used in fishery management, and excessive traps remain in the fishery.

A spatially structured tagging model to estimate movement and fishing mortality rates for the blue shark (Prionace glauca) in the North Atlantic Ocean

2009 ◽  
Vol 60 (10) ◽  
pp. 1029 ◽  
Author(s):  
Alexandre M. Aires-da-Silva ◽  
Mark N. Maunder ◽  
Vincent F. Gallucci ◽  
Nancy E. Kohler ◽  
John J. Hoey
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
The United States ◽  
Mortality Rates ◽  
Fishing Mortality ◽  
Blue Shark ◽  
The North ◽  
Geographical Regions ◽  
The North Atlantic

Large numbers of blue sharks are caught as bycatch, and have even become the target species in pelagic longline fisheries in the North Atlantic Ocean. The status of the stock is ambiguous due to the limitations of the fishery-dependent data. This study presents a spatially structured tagging model to estimate blue shark movement and fishing mortality rates in the North Atlantic Ocean. The model uses the blue shark tag-recovery data collected by the United States National Marine Fisheries Service Cooperative Shark Tagging Program (1965–2004). Four major geographical regions (two on each side of the ocean) are assumed. The blue shark fishing mortality rates (F) were found to be heterogeneous across the four regions. While the estimates of F obtained for the western North Atlantic Ocean were historically lower than 0.1 year–1, the F estimates over the most recent decade (1990s) in the eastern side of the ocean are rapidly approaching 0.2 year–1. Because of the particular life-history of the blue shark, these results suggest careful monitoring of the fishery as the juvenile and pregnant female segments of the stock are highly vulnerable to exploitation in the eastern North Atlantic Ocean.

scholarly journals Large scale, synchronous variability of marine fish populations driven by commercial exploitation

2016 ◽  
Vol 113 (29) ◽  
pp. 8248-8253 ◽  
Author(s):  
Kenneth T. Frank ◽  
Brian Petrie ◽  
William C. Leggett ◽  
Daniel G. Boyce
Keyword(s):  
Marine Fish ◽  
North Atlantic ◽  
Large Scale ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Ocean Dynamics ◽  
Fish Populations ◽  
Fishing Mortality ◽  
Stock Biomass ◽  
Spawning Stock

Synchronous variations in the abundance of geographically distinct marine fish populations are known to occur across spatial scales on the order of 1,000 km and greater. The prevailing assumption is that this large-scale coherent variability is a response to coupled atmosphere–ocean dynamics, commonly represented by climate indexes, such as the Atlantic Multidecadal Oscillation and North Atlantic Oscillation. On the other hand, it has been suggested that exploitation might contribute to this coherent variability. This possibility has been generally ignored or dismissed on the grounds that exploitation is unlikely to operate synchronously at such large spatial scales. Our analysis of adult fishing mortality and spawning stock biomass of 22 North Atlantic cod (Gadus morhua) stocks revealed that both the temporal and spatial scales in fishing mortality and spawning stock biomass were equivalent to those of the climate drivers. From these results, we conclude that greater consideration must be given to the potential of exploitation as a driving force behind broad, coherent variability of heavily exploited fish species.

Salinity and Recruitment of Atlantic Cod (Gadus morhua) in the Newfoundland Region

1993 ◽  
Vol 50 (8) ◽  
pp. 1599-1609 ◽  
Author(s):  
Ransom A. Myers ◽  
Kenneth F. Drinkwater ◽  
Nicholas J. Barrowman ◽  
James W. Baird
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Population Analysis ◽  
Grand Banks ◽  
The North ◽  
Virtual Population ◽  
Stock Biomass ◽  
Spawning Stock ◽  
Recruitment Time

Recruitment predictions for Atlantic cod (Gadus morhua) in the North Atlantic, based upon a previously published regression with salinity, are found to be well correlated with recent recruitment estimates from both virtual population analysis and those derived from research surveys. The addition of spawning stock biomass in the regression significantly increased the percentage of the variance accounted for in the recruitment time series. A similar relationship between recruitment and salinity was found for two nearby stocks (southern Grand Banks and St. Pierre Bank). Oceanographic and food chain mechanisms that might be responsible for a link between salinity and recruitment are discussed.

scholarly journals Evaluation of the exploitation of Eastern Baltic cod (Gadus morhua callarias L.) stock in 1976–1997

2003 ◽  
Vol 60 (5) ◽  
pp. 1114-1122 ◽  
Author(s):  
Krzysztof Radtke
Keyword(s):  
Gadus Morhua ◽  
Management Strategies ◽  
Mortality Rates ◽  
Reference Points ◽  
Fishing Mortality ◽  
Safe Level ◽  
Stock Biomass ◽  
Spawning Biomass ◽  
Eastern Baltic ◽  
Baltic Cod

Abstract Big changes occurred in the Eastern Baltic cod biomass and catches in the 1976–1997 period. At present, the Eastern Baltic cod stock spawning biomass (SSB) and catches are approximately five times lower than their highest ever recorded levels observed in the middle of the 1980s. The reasons for the stock decline, namely low recruitment and high fishing mortality, are widely known and well described in the literature. Throughout the whole period, the International Council for the Exploration of the Sea (ICES) made scientific recommendations regarding the exploitation level of the cod stock. The ICES presented and analysed different management strategies based on fishing mortalities which corresponded to biological reference points (BRP) and also recommended total allowable catches (TACs) for cod, taking into account the sustainability of cod resources. In fact, in most years the TAC established by the International Baltic Sea Fisheries Commission (IBSFC) and cod catches (observed exploitation) exceeded the ICES-recommended TAC and thus their scientific advice was neither taken into account by the IBSFC nor by fishermen. This paper evaluates: (1) the would-be state of the Eastern Baltic cod stock if it had been exploited according to ICES-recommended TAC levels, as compared with observed stock exploitation; and (2) the potential effects of management using fishing mortality rates which correspond to BRP on SSB estimates and catch levels, as compared with observed stock exploitation. It is concluded that if ICES advice had been followed, the cumulative cod catches in the 1976–1997 period would have been the same as those observed, but the stock biomass would have been much higher and at a safe level (SSB above 240 000 t). Furthermore, from the comparative analysis of different management strategies based on BRP and the observed strategy, it appears that other management strategies could have been applied which would have produced a higher biomass and greater cumulative catch numbers than those observed.

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