Biological reference points for sea scallops (Placopecten magellanicus): the benefits and costs of being nearly sessile

2004 ◽  
Vol 61 (8) ◽  
pp. 1338-1354 ◽  
Author(s):  
Stephen J Smith ◽  
Paul Rago
Keyword(s):  
Management Strategies ◽  
Fishing Effort ◽  
Reference Points ◽  
Placopecten Magellanicus ◽  
Nonlinear Mixed Effects Models ◽  
Lower Productivity ◽  
Boom And Bust ◽  
Sea Scallops ◽  
Habitat Damage ◽  
Definition Of

In this paper, we concentrate on spatial aspects of growth and reproduction for sea scallops (Placopecten magellanicus) to advance the general theory for development of reference points for sessile animals and to illustrate the general points with several specific examples. Nonlinear mixed effects models can be used to define the spatial distribution of growth rates and their implications for the definition of growth overfishing. We develop a basin model to illustrate that the typical "boom and bust" effects, often attributed to environmental factors, are explained equally well by spatial variations in habitat quality, spatial concentration of fisheries, and dispersal of larvae among areas. Results suggest that incentives to concentrate fishing effort in lower productivity areas may be an effective tool for reducing recruitment variation and improving yields. Reductions in fishing mortality might be possible with closed areas as they can be used to reduce the concentration of effort on high scallop densities. Further, rotational area management strategies can offer the promise of balancing demands for increased yield, prevention of recruitment overfishing, maintaining spawning reserves, and reducing habitat damage and bycatch.

scholarly journals Shell growth of sea scallops (Placopecten magellanicus) in the southern and northern Great South Channel, USA

2006 ◽  
Vol 63 (5) ◽  
pp. 811-821 ◽  
Author(s):  
Bradley P. Harris ◽  
Kevin D.E. Stokesbury
Keyword(s):  
Shell Growth ◽  
Shell Height ◽  
Management Strategies ◽  
Height Distribution ◽  
Placopecten Magellanicus ◽  
Geographic Scale ◽  
Sea Scallop ◽  
Asymptotic Size ◽  
The Usa ◽  
Sea Scallops

Abstract Shell growth of sea scallops in two commercially productive regions of the Great South Channel (GSC) (41°4′N 69°16′W) was studied using tag–recapture experiments. Commercial fishers captured and returned 9.7% of the 11 704 sea scallops tagged in the southern GSC study area, and 7.9% of the 18 274 sea scallops tagged in the northern GSC study area. Scallop density and shell height distribution were sampled with underwater video in the two study areas. In the southern GSC tagged scallops grew faster, reached larger asymptotic size, and had higher growth performance (Φ′) than in the northern GSC study area. Mean sea scallop density in the southern GSC was 0.117 scallops m−2 (s.e. = 0.01), and 2.601 scallops m−2 (s.e. = 0.28) in the northern GSC. Environmental factors, fishing pressure, and sea scallop density all influence shell growth on a fine geographic scale (1–100 km2) and should be considered in area-specific management strategies, such as that currently used in the USA sea scallop fishery.

Managing growth overfishing with multiannual compromise strategies

1997 ◽  
Vol 54 (10) ◽  
pp. 2255-2276 ◽  
Author(s):  
P Marchal
Keyword(s):  
Management Strategies ◽  
Fishing Effort ◽  
Reference Points ◽  
Long Term Outcomes ◽  
Northeast Atlantic ◽  
Factors Influencing ◽  
Optimal Balance ◽  
Short And Long Term ◽  
Mobile Target

Most of the Northeast Atlantic stocks are currently fished above the biological reference points (e.g., Fmax). In attempting to achieve such targets, advisers and managers have faced two main problems. First, it is impractical to (i) simultaneously maximize yields, stabilize fisheries, and safeguard stocks and (ii) optimize both short- and long-term outcomes for the industry. Second is the lack of predictability, several years ahead, in factors influencing decisions. This study addresses these twin issues by exploring the relative performances of various multiannual and compromise (or composite) management strategies. Multiannual fishing efforts are set in advance for a ``resolution'' period of several years, at the end of which they are updated. They are calculated to satisfy a prior weighted compromise amongst three criteria: (i) minimizing fishing effort variability, (ii) minimizing catch variability, and (iii) reaching a ``mobile target:'' the latter is defined with a second weighted compromise between the long-term target and the fishing effort at the beginning of the resolution period. A safe and optimal balance between all the short- and long-term fishery outcomes is found with a 5-year resolution period, during which the mobile target is split into 40-60% of the long-term target, and 60-40% of the fishing effort at the start of the resolution period, while criteria i, ii, and iii are weighted equally.

scholarly journals Immediate maximum economic yield; a realistic fisheries economic reference point

2009 ◽  
Vol 67 (3) ◽  
pp. 577-582 ◽  
Author(s):  
Jordi Lleonart ◽  
Gorka Merino
Keyword(s):  
Reference Point ◽  
Fishing Effort ◽  
Reference Points ◽  
Economic Rent ◽  
Short Term ◽  
Fishing Season ◽  
Shrimp Fishery ◽  
Maximum Economic Yield ◽  
Nw Mediterranean ◽  
Definition Of

Abstract Lleonart, J., and Merino, G. 2010. Immediate maximum economic yield; a realistic fisheries economic reference point. – ICES Journal of Marine Science, 67: 577–582. Unregulated or poorly managed fisheries tend towards overexploitation, but fisheries rent does not completely dissipate when immediate rent maximization is sought. The principle of immediate economic rent maximization is the basis of the derivation of a classic model and has led to the definition of a relationship in a catch-and-effort diagram termed the dynamic immediate maximum economic yield (DIMEY) curve. For any initial biomass, if the economic rent in the immediate fishing season is maximized, then the fishing effort and catch strategy that follows will be located on the DIMEY curve. The DIMEY curve is not only used for dynamic simulation but also used to identify a new reference point, the immediate maximum economic yield (IMEY), which is proposed as more realistic than the classic open-access solution for unregulated fisheries. IMEY is proposed as an asymptotic outcome for unregulated or poorly managed fisheries when short-term economic objectives drive fleet activities. IMEY properties are described and compared with traditional fisheries reference points in the yield-and-effort diagram. Theoretical conclusions are compared with empirical evidence provided by the red shrimp fishery off Blanes, Spain (NW Mediterranean). Observed catch-and-effort records are plotted and were positively correlated with the DIMEY curve and IMEY.

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 Consequences of growth variation in northern Baltic herring for assessment and management

2004 ◽  
Vol 61 (3) ◽  
pp. 338-350 ◽  
Author(s):  
Mika Rahikainen ◽  
Robert L. Stephenson
Keyword(s):  
Baltic Sea ◽  
Stock Assessment ◽  
Management Strategies ◽  
Reference Points ◽  
Common Reference ◽  
Baltic Herring ◽  
Marked Variability ◽  
Growth Variation ◽  
Definition Of ◽  
The Impact

Abstract Growth rates of herring in the northern Baltic Sea differ among areas, and have changed substantially over time in some areas in response to environmental change. Weight-at-age of adult herring in some areas of the Finnish herring fishery fluctuated by as much as 60% over the past three decades. Elsewhere, there have been similar but more subtle changes. Growth variation has implications for stock assessment and management: differences suggest a need for considering a smaller spatial structure, at least at the scale of the ICES subdivision, in the case of northern Baltic herring. Changes in growth have an impact on the calculation and use of common biological reference points, and erode the capability of yield projections beyond the short term. Investigation of the impact of growth variation on common reference points of northern Baltic herring revealed that F0.1 was a robust reference despite the marked variability in growth, whereas Fx%SPR (e.g. F35%SPR) was less robust, depending on the definition of maximum spawning-per-recruit. Herring in different areas of the northern Baltic Sea probably require different reference points and possibly different management strategies, as a consequence of differences and variability in growth characteristics.

Where do we draw the line? A simulation approach for evaluating management of marine fish stocks with isolation-by-distance stock structure

2015 ◽  
Vol 72 (7) ◽  
pp. 968-982 ◽  
Author(s):  
Ingrid Spies ◽  
Paul D. Spencer ◽  
André E. Punt
Keyword(s):  
Marine Fish ◽  
Isolation By Distance ◽  
Management Strategies ◽  
Marine Species ◽  
Fishing Effort ◽  
Stock Structure ◽  
Pacific Cod ◽  
Entire Area ◽  
Lower Productivity ◽  
Management Protocol

There is no established management protocol for stocks subject to isolation-by-distance (IBD) stock structure. This study examines several management strategies for two marine fish species subject to IBD using simulation: Pacific cod (Gadus macrocephalus) in the Aleutian Islands (AI) and northern rockfish (Sebastes polyspinis) in the Eastern Bering Sea (EBS) and AI. A one-dimensional stepping stone model was used to model IBD and was intended to mimic regions where marine species are exploited along a continental shelf. The performance of spatial assessment and management methods depended on how the range was split. Splitting anywhere within the managed area led to fewer demes falling below target and threshold biomass levels and higher yield than managing the entire area as a single unit. Equilibrium yield was maximized when each deme was assessed and managed separately and under catch cascading, in which harvest quotas within a management unit are spatially allocated based upon the distribution of survey biomass. The longer-lived rockfish declined more slowly than Pacific cod and experienced greater depletion in biomass under disproportionate fishing effort because of lower productivity. Overall, splitting a management area of the size simulated in the model improved performance measures, and the optimal management strategy grouped management units by demes with similar relative fishing effort.

scholarly journals The impact of commercial fishing on the determination of habitat associations for sea scallops (Placopecten magellanicus, Gmelin)

2009 ◽  
Vol 66 (9) ◽  
pp. 2043-2051 ◽  
Author(s):  
Stephen J. Smith ◽  
Jerry Black ◽  
Brian J. Todd ◽  
Vladimir E. Kostylev ◽  
Mark J. Lundy
Keyword(s):  
Variance Reduction ◽  
Survey Design ◽  
Fishing Effort ◽  
Habitat Associations ◽  
Commercial Fishing ◽  
Placopecten Magellanicus ◽  
Bottom Type ◽  
Sea Scallops ◽  
The Impact

Abstract Smith, S. J., Black, J., Todd, B. J., Kostylev, V. E. and Lundy, M. J. 2009. The impact of commercial fishing on the determination of habitat associations for sea scallops (Placopecten magellanicus, Gmelin). – ICES Journal of Marine Science, 66: 2043–2051. The sea scallop (Placopecten magellanicus) population off southwestern Nova Scotia in Scallop Fishing Area 29 has been monitored by an annual drag survey since the fishery started there in 2001. A new stratification scheme based on surficial geology maps from a multibeam bottom mapping and geology ground-truth project completed in 2004 in the area have been used for survey design since 2005. Survey data from before 2005 have been post-stratified using the new strata. The efficiency of the design with respect to variance reduction appears to have diminished over time suggesting that the association between scallop abundance and bottom type may not have been as strong or constant as first assumed. Modelling of the association between scallop abundance and bottom type and depth using a Bayesian hierarchical approach confirms this diminishing relationship. Comparison of the results from the model with spatial measures of fishing effort based on satellite vessel monitoring data suggests that increasing exploitation may be masking the relationships as scallop beds are targeted and fished down. These results could have implications on the interpretation of species habitat associations from areas where data are only available from periods when the populations have been exploited over a long time. In these cases, the spatial distribution of fishing effort may be a better indicator of species habitat associations than the estimates from surveys.

scholarly journals Subjective judgement in data subsetting: implications for CPUE standardisation and stock assessment of non-target chondrichthyans

2011 ◽  
Vol 62 (6) ◽  
pp. 734 ◽  
Author(s):  
J. M. Braccini ◽  
M.-P. Etienne ◽  
S. J. D. Martell
Keyword(s):  
Ad Hoc ◽  
Stock Assessment ◽  
Fishing Effort ◽  
Reference Points ◽  
Fish Stock ◽  
Model Parameters ◽  
Total Allowable Catch ◽  
Subjective Judgement ◽  
Definition Of ◽  
Catch Per Effort

Standardisation of catch-per-effort (CPUE) data is an essential component for nearly all stock assessments. The first step in CPUE standardisation is to separate the comparable from the non-comparable catch and effort records and this is normally done based on subjective rules. In the present study, we used catch-and-effort data from the elephant fish (Callorhinchus milii) to illustrate the differences in CPUE when using expert judgement to define different ad hoc selection criteria used to subset these data. The data subsets were then used in the standardisation of CPUE and the stock assessment of elephant fish. The catch-and-effort subsets produced different patterns of precision and trends, each of which led to different estimates (and related uncertainty) of model parameters and management reference points. For most CPUE series, there was a very high probability that the elephant fish stock is overexploited and that overfishing is occurring. The estimates of total allowable catch (TAC) and the uncertainty around these estimates also varied considerably depending on the CPUE series used. Our study shows how sensitive TAC estimation is when there is high uncertainty in the definition of the fishing effort targeted at the species analysed.

scholarly journals Implications of climate change for the management of North Sea cod (Gadus morhua)

2005 ◽  
Vol 62 (7) ◽  
pp. 1483-1491 ◽  
Author(s):  
Laurence T. Kell ◽  
Graham M. Pilling ◽  
Carl M. O'Brien
Keyword(s):  
Climate Change ◽  
North Sea ◽  
Gadus Morhua ◽  
Stock Assessment ◽  
Management Strategies ◽  
Fishing Effort ◽  
Reference Points ◽  
Fishing Mortality ◽  
Short Term ◽  
Management Procedures

Abstract Robustness of both short-term stock biomass recovery and longer-term sustainable management strategies to different plausible climatic change scenarios were evaluated for North Sea cod (Gadus morhua), where climate was assumed to impact growth and recruitment. In the short term, climate change had little effect on stock recovery, which depends instead upon reducing fishing effort to allow existing year classes to survive to maturity. In the longer term, climate change has greater effects on stock status, but higher yields and biomass can be expected if fishing mortality is reduced. Incorporating environmental covariates in stock assessment predictions will not achieve sustainable resource use. The implications of climate change for biological reference points depend upon the mechanism through which temperature acts on recruitment, i.e. on juvenile survival or carrying capacity. It is not possible to distinguish between these processes with stock assessment data sets alone. However, this study indicates that reference points based on fishing mortality appear more robust to uncertainty than those based on biomass. Ideally, simpler management procedures are required that meet pre-agreed management objectives and are robust to uncertainty about the true dynamics.

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