How fisher behavior can bias stock assessment: insights from an agent-based modeling approach

2020 ◽  
Vol 77 (11) ◽  
pp. 1794-1809
Author(s):  
Steven Saul ◽  
Elizabeth N. Brooks ◽  
David Die
Keyword(s):  
Stock Assessment ◽  
Fish Population ◽  
Dependent Data ◽  
Commercial Fishing ◽  
Fishing Activity ◽  
Agent Based ◽  
Dependent Observations ◽  
Sampling Protocols ◽  
Fishing Fleets ◽  
Fisher Behavior

During stock assessment, fishery-dependent observations are often used to develop indices of abundance or biomass from catch per unit of effort (CPUE) and contribute catch at size or age information. However, fisher behavior, rather than scientific sampling protocols, determines the spatial and temporal locations of fishery-dependent observations. As a result, trends from fishery-dependent data may be a function of fishing activity rather than fish population changes. This study evaluates whether data collected from commercial fishing fleets in the Gulf of Mexico are representative of trends in fish population size. A coupled bioeconomic agent-based model was developed to generate simulated fishery data, which were used to populate an age-structured stock assessment. Comparison of stock assessment results with simulated fish population dynamics showed that management advice from assessment models based on fishery-dependent data could be biased. Assessment of fish with small home ranges harvested by fishing fleets that frequent the same fishing grounds could cause overestimation of fishing mortality. Not accounting for the spatial structure of the fishers or fish can cause biased estimates of population status.

scholarly journals Accounting for spatiotemporal variation and fisher targeting when estimating abundance from multispecies fishery data

2017 ◽  
Vol 74 (11) ◽  
pp. 1794-1807 ◽  
Author(s):  
James T. Thorson ◽  
Robert Fonner ◽  
Melissa A. Haltuch ◽  
Kotaro Ono ◽  
Henning Winker
Keyword(s):  
Stock Assessment ◽  
Spatial Scales ◽  
Spatiotemporal Variation ◽  
Dynamic Factor ◽  
Fishing Activity ◽  
Fisheries Science ◽  
Catch Rates ◽  
Multiple Species ◽  
Fishing Behavior ◽  
Fisher Behavior

Estimating trends in abundance from fishery catch rates is one of the oldest endeavors in fisheries science. However, many jurisdictions do not analyze fishery catch rates due to concerns that these data confound changes in fishing behavior (adjustments in fishing location or gear operation) with trends in abundance. In response, we developed a spatial dynamic factor analysis (SDFA) model that decomposes covariation in multispecies catch rates into components representing spatial variation and fishing behavior. SDFA estimates spatiotemporal variation in fish density for multiple species and accounts for fisher behavior at large spatial scales (i.e., choice of fishing location) while controlling for fisher behavior at fine spatial scales (e.g., daily timing of fishing activity). We first use a multispecies simulation experiment to show that SDFA decreases bias in abundance indices relative to ignoring spatial adjustments and fishing tactics. We then present results for a case study involving petrale sole (Eopsetta jordani) in the California Current, for which SDFA estimates initially stable and then increasing abundance for the period 1986–2003, in accordance with fishery-independent survey and stock assessment estimates.

AZOV SEA VIMBA INDICATOR ASSESSMENT OF THE STATE OF FISH POPULATION IN TERMS OF LACK OF BIOLOGICAL DATA BY LBI MODEL

Fisheries ◽  
2021 ◽  
Vol 2021 (3) ◽  
pp. 68-75
Author(s):  
Inna Kozobrod ◽  
M. Pyatinsky ◽  
Elena Vlasenko
Keyword(s):  
Stock Assessment ◽  
Fish Population ◽  
Maximum Sustainable Yield ◽  
Biological Data ◽  
Reference Points ◽  
Population Characteristics ◽  
Small Scale ◽  
Assessment Procedure ◽  
Indicator Method ◽  
Yield Level

Stock assessment of vimba population Vimba vimba (Linnaeus, 1758) in period 2015–2020 was performed by qualitative indicator method LBI (Length-Based Indicators) that allows to assess qualitative characteristics of the population and fisheries and MSY biological reference points. The indicator, qualitative approach to stock assessment was applied due to absence vimba population of stable stock-recruitment relationship (due to artificial reproduction exist), which makes impossible to apply surplus production approach to solve production equation dB/dt. LBI model was performed based on available length-weight vimba frequencies dynamics information, which allows to evaluate qualitative population characteristics and fisheries impact. Model results shows no overexploitation signals: in period 2015–2020 fisheries are carried out in maximum sustainable yield level. Indicator results according to reference points indicate no significant signals of reduction optimal length class (Lopt), small-size or large-size class. In 2016 and 2018 uncertain overexploitation of small-scale classes leads to no significant changes was underlined. In terms of biological and fisheries data lacking, LBI methods allow to perform stock assessment procedure more stable and robust then surplus or cohort approach, and output scientific advice to fisheries management.

scholarly journals The value of commercial fish size distribution recorded at haul by haul compared to trip by trip

2020 ◽  
Author(s):  
Kristian S Plet-Hansen ◽  
François Bastardie ◽  
Clara Ulrich
Keyword(s):  
Fishing Effort ◽  
Fish Distribution ◽  
Minimum Size ◽  
Dependent Data ◽  
Commercial Fishing ◽  
Commercial Fish ◽  
Traceability System ◽  
Fishing Vessels ◽  
Set Up ◽  
Abundance And Distribution

Abstract Data from commercial fishing vessels may enhance the range of observations available for monitoring the marine environment. However, effort and catch data provide information on fish distribution with a bias due to spatial targeting and selectivity. Here, we measured the shortcomings of standard fishery-dependent data and advocate for the utilization of more precise datasets indirectly collected by the commercial fishery. Data from a Danish traceability system, which records size of commercial fish at the haul level, are held against the set-up of current eLog and sales slips’ data collected for the Danish fisheries. We showed that the most accurate mapping of the spatial distribution of catches per size group is not only possible through size records collected at the haul level but also by high resolution on fishing effort data. In Europe, the regulation to land all catches with a quota or minimum size limit, including unwanted, has increased the focus on avoidance and discards; we show the potential of such data sources to inform on fish abundance and distribution, especially of importance where fishery-dependent data are the only source of information.

Another New Zealand centenarian: age validation of black cardinalfish (Epigonus telescopus) using lead–radium and bomb radiocarbon dating

2017 ◽  
Vol 68 (2) ◽  
pp. 352 ◽  
Author(s):  
Dianne M. Tracey ◽  
Allen H. Andrews ◽  
Peter L. Horn ◽  
Helen L. Neil
Keyword(s):  
New Zealand ◽  
Growth Zone ◽  
Commercial Fishing ◽  
Age Validation ◽  
Fishing Activity ◽  
Combined Application ◽  
Bomb Radiocarbon ◽  
Otolith Core ◽  
Radiometric Ages ◽  
Lead 210

Black cardinalfish (Epigonus telescopus, Apogonidae) is an important component of deepsea commercial fishing activity in the New Zealand region. It is estimated to live longer than 100 years on the basis of counts of unvalidated annual growth zones in otoliths. Age-validation procedures for long-lived fishes are often one of the following two techniques: (1) lead–radium disequilibria, which uses the natural decay of radium-226 into lead-210 as a natural clock; or (2) bomb radiocarbon (Δ14C) dating, which relies on the marine signal created by nuclear testing. The high estimated lifespan, as well as the large size of the otolith core region, make E. telescopus an excellent candidate for a combined application of these two independent age-validation techniques. The lead–radium dating using otolith cores indicated that growth-zone counts less than ~60 years were consistent with radiometric ages, whereas higher counts appeared to be under-estimates. There was 95% confidence that maximum age was at least 95 years. The validation indicated that fish aged over 60 years tended to be under-aged by up to 30%. The bomb radiocarbon levels in otolith cores supported age estimates up to ~40 years made from zone counts, and by inference from the zone counts validated with lead–radium dating, longevity exceeds 100 years.

scholarly journals Establishing stakeholder connections for management of the Irish orange roughy fishery

2006 ◽  
Vol 64 (4) ◽  
pp. 841-845 ◽  
Author(s):  
Samuel Shephard ◽  
Paul Connolly ◽  
Nils-Roar Hareide ◽  
Emer Rogan
Keyword(s):  
Stock Assessment ◽  
Management Plan ◽  
Scientific Data ◽  
Commercial Fishing ◽  
Negative Effects ◽  
Management Options ◽  
Orange Roughy ◽  
Fishing Strategies ◽  
Informal Discussion ◽  
Assessment Survey

Abstract S. Shephard, P. Connolly, N.-R. Hareide, and E. Rogan. 2007. Establishing stakeholder connections for management of the Irish orange roughy fishery. – ICES Journal of Marine Science, 64: 841–845. In 2000, an Irish fishery for orange roughy commenced in ICES Subarea VII. Landings peaked at >5000 t in 2002, but the fishery was largely closed from January 2005 because of concern about unsustainable fishing and the negative effects on deepwater sharks and coral. A multidimensional project was initiated in 2003 to investigate the fishery system and to develop a management plan. The project emphasized the establishment of productive relationships with stakeholders, particularly fishers. We describe and evaluate the process by which such linkages were developed successfully. Informal discussion with fishers produced experiential knowledge that described fishery development and fishing strategies, and informed subsequent scientific data collection. Strengthening relationships permitted access to commercial fishing trips and cooperation in research. An atmosphere developed in which management options could be debated in both wheelhouse and boardroom. Eventually, a formal research/stock assessment survey took place in which fishers, agencies, and deepwater coral ecologists cooperated.

Evaluation of spatiotemporal imputations for fishing catch rate standardization

2017 ◽  
Vol 74 (9) ◽  
pp. 1348-1361
Author(s):  
Ross J. Marriott ◽  
Berwin A. Turlach ◽  
Kevin Murray ◽  
David V. Fairclough
Keyword(s):  
High Growth ◽  
Catch Rate ◽  
Commercial Fishing ◽  
Data Sets ◽  
Rate Data ◽  
Fishing Activity ◽  
Fish Stocks ◽  
Base Method ◽  
Catch Rates ◽  
Over Time

As commercial fishing activity shifts to target different grounds over time, spatial gaps can be created in catch rate data, leading to biases in derived indices of fish abundance. Imputation has been shown to reduce such biases. In this study, the relative performance of several imputation methods was assessed using simulated catch rate data sets. Simulations were carried out for three fish stocks targeted by a commercial hook-and-line fishery off the southwestern coast of Australia: snapper (Chrysophrys auratus), West Australian dhufish (Glaucosoma hebraicum), and baldchin groper (Choerodon rubescens). For high-growth scenarios, the mean squared errors (MSEs) of geometric and linear imputations were lower, indicating higher accuracy and precision than that for base method (constant value) imputations. For low-growth scenarios, the lowest MSEs were achieved for base method imputations. However, for the final standardized and imputed abundance indices, the base method index consistently demonstrated the largest biases. Our results demonstrate the importance of selecting an appropriate imputation method when standardizing catch rates from a commercial fishery that has changed its spatial pattern of fishing over time.

Dynamic hypoxic zones in Lake Erie compress fish habitat, altering vulnerability to fishing gears

2015 ◽  
Vol 72 (6) ◽  
pp. 797-806 ◽  
Author(s):  
Richard T. Kraus ◽  
Carey T. Knight ◽  
Troy M. Farmer ◽  
Ann Marie Gorman ◽  
Paris D. Collingsworth ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Lake Erie ◽  
Scale Effects ◽  
Stock Assessment ◽  
Fish Habitat ◽  
Fish Distribution ◽  
Commercial Fishing ◽  
Hypoxic Conditions ◽  
Fishing Gears ◽  
Catch Rates

Seasonal degradation of aquatic habitats from hypoxia occurs in numerous freshwater and coastal marine systems and can result in direct mortality or displacement of fish. Yet, fishery landings from these systems are frequently unresponsive to changes in the severity and extent of hypoxia, and population-scale effects have been difficult to measure except in extreme hypoxic conditions with hypoxia-sensitive species. We investigated fine-scale temporal and spatial variability in dissolved oxygen in Lake Erie as it related to fish distribution and catch efficiencies of both active (bottom trawls) and passive (trap nets) fishing gears. Temperature and dissolved oxygen loggers placed near the edge of the hypolimnion exhibited much higher than expected variability. Hypoxic episodes of variable durations were frequently punctuated by periods of normoxia, consistent with high-frequency internal waves. High-resolution interpolations of water quality and hydroacoustic surveys suggest that fish habitat is compressed during hypoxic episodes, resulting in higher fish densities near the edges of hypoxia. At fixed locations with passive commercial fishing gear, catches with the highest values occurred when bottom waters were hypoxic for intermediate proportions of time. Proximity to hypoxia explained significant variation in bottom trawl catches, with higher catch rates near the edge of hypoxia. These results emphasize how hypoxia may elevate catch rates in various types of fishing gears, leading to a lack of association between indices of hypoxia and fishery landings. Increased catch rates of fish at the edges of hypoxia have important implications for stock assessment models that assume catchability is spatially homogeneous.

scholarly journals Discard mortality rates in the Bering Sea snow crab, Chionoecetes opilio, fishery

2015 ◽  
Vol 72 (5) ◽  
pp. 1525-1529 ◽  
Author(s):  
J. Daniel Urban
Keyword(s):  
Mortality Rate ◽  
Bering Sea ◽  
Fishery Management ◽  
Stock Assessment ◽  
Mortality Rates ◽  
Snow Crab ◽  
Commercial Fishing ◽  
Chionoecetes Opilio ◽  
Discard Mortality ◽  
The Bering Sea

Abstract Fish and invertebrates that are unintentionally captured during commercial fishing operations and then released back into the ocean suffer mortality at unknown rates, introducing uncertainty into the fishery management process. Attempts have been made to quantify discard mortality rates using reflex action mortality predictors or RAMP which use the presence or absence of a suite of reflexes to predict discard mortality. This method was applied to snow crab, Chionoecetes opilio, during the 2010–2012 fisheries in the Bering Sea. Discard mortality in the fishery is currently assumed to be 50% in stock assessment models, but that rate is not based on empirical data and is widely recognized to be in need of refinement. Over 19 000 crab were evaluated using the RAMP method. The estimated discard mortality rate was 4.5% (s.d. = 0.812), significantly below the rate used in stock assessment models. Predicted discard mortality rates from the 2010 to 2012 study were strongly correlated with the air temperature at the St Paul Island airport in the Pribilof Islands. Using this relationship, the discard mortality rate from 1991 to 2011 was estimated at 4.8% (s.d. = 1.08).

Business as usual for the human use of Moreton Bay following marine park zoning

2018 ◽  
Vol 69 (2) ◽  
pp. 277 ◽  
Author(s):  
R. A. Kenyon ◽  
R. C. Babcock ◽  
Q. Dell ◽  
E. Lawrence ◽  
C. Moeseneder ◽  
...  
Keyword(s):  
Significant Proportion ◽  
Recreational Fishing ◽  
Commercial Fishing ◽  
Multiple Use ◽  
Fishing Activity ◽  
Moreton Bay ◽  
Marine Park ◽  
Eastern Australia ◽  
Before And After ◽  
Human Use

The multiple-use Moreton Bay Marine Park in eastern Australia was rezoned in 2009, increasing the total no-take marine national park (MNP) from 0.5 to 16%. In the present study we measured trends in the human use of no-take areas using observed vessel position and categorisation during on-water and aerial surveys before and after rezoning. Measured changes in spatial patterns of fishing showed that the effects of rezoning on most fishing activity was minimal. After rezoning, the proportion of recreational fishing declined from 6.3 to 2.6% of the footprint in the new MNPs. The proportion of commercial fishing declined from 25 to 1%, although the amount of commercial fishing was low. There was an overall increase in fishing activity on Moreton Bay. Low recreational fisher displacement suggests that the expansion of the MNP area did not have a high social cost. However, most of the no-take zones were areas not previously subject to high recreational fishing pressure. If a significant proportion of the no-take zones were placed in areas of low ecological production, the biodiversity conservation impact achieved by the rezoning of Moreton Bay may have been less than the 16% increase in no-take areas would imply.

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