Changes In Catch Rates Research Articles

Local ecological knowledge can support improved management of small-scale fisheries in the Bay of Bengal

Fishers’ local ecological knowledge (LEK) can be used to reconstruct or supplement long-term trends in heavily exploited population or poorly assessed species with low biomass. We used historical memories of small-scale fishers to understand their perceptions of changes in catch trends in marine fisheries over the last 20 years. The study aimed at evaluating how fishers could provide consistent and reliable data on major fish species/groups comparable with official catch data and to explore the potential of increasing their participation in fishery management. We conducted focus group discussions (FGDs) and key informant interviews with experienced fishers and stakeholders, using a structured template related to the catch and effort data. Using FGD data, we systematically compared changes in fish catch rates and effort over time and space. Data were collected on major groups of species that had reasonable landing over time. Overall, the analysis revealed changes in catch rate, monthly landings per landing center, factors that likely influence the catch trends, and the spatial expansion of fisheries. Our study provides insight into species’ abundance over time. Fishers’ LEK shows declining catch rates for major species and groups, but monthly harvests at landing centers have increased over two decades because of increased fishing efforts. Small-scale fishers are catching more fish from deeper waters over time, indicating a geographical expansion and/or development of fisheries beyond traditionally exploited areas. Such expansions of nearshore fisheries may result from the overfishing of nearby areas. On the contrary, this could be viewed as a positive indication of the potential for growth and development of small-scale fisheries in the region, especially in the context of the blue economy. The agreement between official statistics and fishers’ data on species catch trends over time suggests that fishers have a good understanding of their fishing system. This indicates that fishers’ knowledge could be invaluable, especially in data-poor areas. LEK integration into policy and management is thus expected to facilitate the efficient management of small-scale fisheries.

How climate change and climate variability affected trip distance of a commercial fishery

Changes in climate factors affect the distribution of various tuna species differently due to their unique physiological adaptations and preferred habitats. As the resulting spatial distributions of tunas alter in response to climate change and climate variability, the distribution of fishing effort will, in turn, be affected. This study uses a quantitative model to estimate the impacts of SST and ENSO events on trip distance of the Hawaii deep-set longline fleet between 1991 and 2020. The results show that the higher the SST of the fishing grounds of the Hawaii longline fleet, the longer trip distance; whereas ENSO events could result in shorter trip distance, possibly due to changes in catch rates of different tuna species through spatial redistribution during El Niño and La Niña events.

Comparing fishery-independent and fishery-dependent data for analysis of the distributions of Oregon shelf groundfishes

We investigate whether fishery-dependent time series can be used to fill in spatial and temporal data gaps where scientific, fishery-independent data are not available. Limitations in sampling coverage combined with a historical focus on continental slope-dwelling groundfish resulted in a gap in understanding Oregon’s nearshore groundfish fishery. Although fisheries-independent surveys have been conducted across most of the fishery’s depth range, the data are limited by years and seasons surveyed, as well as the absence of data for areas shallower than 55 m water depth. Fishery-dependent data are available for those shallow waters and for a broader temporal range. However, these data are self-reported and the coverage was determined by where fishers choose to fish. To investigate the potential for future combined uses for these data sources, we analyzed spatial and temporal changes in catch rates, as well as gaps in fishery (logbook) and scientific (NOAA survey) data, for six flatfishes. We found that more heavily targeted species that live in deeper water, like Dover sole and petrale sole, had more spatial scientific sampling coverage compared to less frequently targeted species that live in shallow water, such as starry flounder and sand sole. Overlap between datasets was variable in space and time but consistently higher near large ports. We identified the winter season, and the pre-2003 time-period as having the highest potential to benefit from complementary use of fishery-dependent data. Prior to 2003, the survey design was variable and there was greater spatial and temporal coverage of logbook data compared to post-2003. Integration of these data sets may be useful for future research given their differences in spatial and temporal range. This work provides a new perspective on the value of using fishery-dependent data to understand the spatial distribution of species in habitats that are under sampled in scientific surveys.

Spillover benefits from the world's largest fully protected MPA.

Previous research has cast doubt on the potential for marine protected areas (MPAs) to provide refuge and fishery spillover benefits for migratory species as most MPAs are small relative to the geographic range of these species. We test for evidence of spillover benefits accruing from the world's largest fully protected MPA, Papahānaumokuākea Marine National Monument. Using species-specific data collected by independent fishery observers, we examine changes in catch rates for individual vessels near to and far from the MPA before and after its expansion in 2016. We find evidence of spillover benefits for yellowfin (Thunnus albacares) and bigeye tuna (Thunnus obesus).

Angler Choices That Help Catch Lots of Big Fish

A primary goal of fisheries management is to maximize angler satisfaction (e.g., by catching more and bigger fish), while maintaining sustainable populations. In addition to environmental and ecological factors, angler choices may influence recreational catches. Using interviews (92,838) from Walleye (Sander vitreus) anglers in Lake Erie during 1989-2017, we identified how angler behavior influences catch outcomes. Angler behaviors were associated with changes in catch rate and the length of harvested fish. For example, trolling resulted in a 50% increase in median catch and 24 mm increase in length, relative to casting. Other behaviors led to tradeoffs between catch rate and size, such as the time of year anglers fished. We identified behaviors that maximize fishing success with respect to anglers’ desired catch outcomes. Our results can help increase angler satisfaction by providing realistic catch expectations given environmental and fishery conditions, while improving recreational catch outcomes through more informed angler-decision making.

Net illumination reduces fisheries bycatch, maintains catch value, and increases operational efficiency

Small-scale fisheries are vital for food security, nutrition, and livelihoods in coastal areas throughout the world's oceans.1-9 As intricately linked social-ecological systems, small-scale fisheries require management approaches that help ensure both ecological and socioeconomic sustainability.7,10-14 Given their ease of use and lucrative nature, coastal gillnet fisheries are globally ubiquitous.10,15 However, these fisheries often result in high discarded capture of non-target organisms (bycatch) that can lead to significant cascading effects throughout trophic chains16-18 and costly fisheries restrictions that result in important revenue losses in coastal communities with scarce economic alternatives.19,20 Despite these challenges, few solutions have been developed and broadly adopted to decrease bycatch in coastal gillnet fisheries, particularly in developing nations.5,21 Here we used controlled experiments along Mexico's Baja California peninsula to show that illuminating gillnets with green LED lights-an emerging technology originally developed to mitigate sea turtle bycatch-significantly reduced mean rates of total discarded bycatch biomass by 63%, which included significant decreases in elasmobranch (95%), Humboldt squid (81%), and unwanted finfish (48%). Moreover, illuminated nets significantly reduced the mean time required to retrieve and disentangle nets by 57%. In contrast, there were no significant differences in target fish catch or value. These findings advance our understanding of how artificial illumination affects operational efficiency and changes in catch rates in coastal gillnet fisheries, while illustrating the value of assessing broad-scale ecological and socioeconomic effects of species-specific conservation strategies.

Effects of 3D seismic surveying on snow crab fishery

Commercial Snow Crab (Chionoecetes opilio) harvesters believe marine noise from seismic surveys reduces commercial Snow Crab catch rates. Depending on the type of seismic survey used, animals living in a particular area could be exposed to loud noise (e.g. daily Sound Exposure Level (SEL) >165 dB re 1 μPa2·s) for periods ranging from hours (typical 2D survey) to months (detailed 3D survey). This field experiment applied a series of comparisons conducted within a Before-After-Control-Impact study design to investigate the effect of prolonged industrial 3D seismic exposure on the catch rates of Snow Crab over nine weeks in 2017 and five weeks in 2018. Changes in catch rates at 3D seismic surveying sites were inconsistent across years, with reduced catches in 2017 and increased catches in 2018. Catch rates were similar at experimental and control sites within two weeks after exposure, and the potential effect of seismic surveying was not measured at a distance of 30 km. The large variation in catch rates across small temporal and spatial scales coupled with the absence of notable mechanistic responses of Snow Crab in past studies to seismic in associated snow crab movement behavior, gene expression and physiology, we conclude that the observed differences owing to seismic surveying in our study design are likely a result of stochastic processes external to our manipulation.

Spatio-temporal changes in catch rates of pelagic sharks caught by Japanese research and training vessels in the western and central North Pacific

Blue shark and shortfin mako are key pelagic shark species distributed throughout the temperate and tropical waters of the world’s oceans. These species are caught in the North Pacific by Japanese longline fisheries as bycatch and occasionally targeting blue shark. Japanese research and training vessels (JRTVs) have been collecting fishery-independent data on these sharks in the western and central North Pacific since 1992. However, the catch per unit of effort (CPUE) estimated from the fishery-independent data had not been used for stock assessments due to an issue concerning reporting after the 2000s. In this study, a statistical filtering method was used to remove unreliable set-by-set data collected by JRTVs. The nominal CPUE of the JRTVs was then standardized using the spatio-temporal generalized linear mixed model to provide the spatial and temporal changes in the CPUEs of these sharks in the North Pacific. The hotspots of blue shark appeared in temperate waters of the western and central North Pacific, whereas those of shortfin mako were distributed in coastal and offshore waters along the Kuroshio-Oyashio transition zone and the Mixed Water Region. The yearly changes in the CPUE of blue shark illustrated a downward trend until 2008 and an upward trend thereafter, whereas those of shortfin mako exhibited a flat trend with large fluctuations from 1994 to 2008, and a down-and-up trend thereafter. The information predicted from the fishery-independent data is very useful for improving the stock assessment and management of these sharks as it provides an understanding of spatio-temporal changes in the hotspots and temporal changes in the catch rates.

Effect of fishing effort on catch rate and catchability of largemouth bass in small impoundments

AbstractLargemouth bass Micropterus salmoides (Lacepède) catch rates decline with sustained fishing effort, even without harvest. It is unclear why declines in catch rate occur, and little research has been directed at how to improve catch rate. Learning has been proposed as a reason for declining catch rate, but has never been tested on largemouth bass. If catch rate declines because fish learn to avoid lures, periods of no fishing could be a management tool for increasing catch rate. In this study, six small impoundments with established fish populations were fished for two May to October fishing seasons to evaluate the effect of fishing effort on catch rate. Closed seasons were implemented to test whether a 2‐month period of no fishing improved catch rates and to determine whether conditioning from factors other than being captured reduced catch rate. Mixed‐model analysis indicated catch rate and catchability declined throughout the fishing season. Catch rate and catchability increased after a 2‐month closure but soon declined to the lowest levels of the fishing season. These changes in catch rate and catchability support the conclusion of learned angler avoidance, but sustained catchability of fish not previously caught does not support that associative or social learning affected catchability.

Changes in Fish Catch Rates in the Presence of Air Gun Sounds in Prudhoe Bay, Alaska

Air guns used in oil industry seismic surveys have the capacity to change fish catch rates, but no previous work has demonstrated this effect in shallow water or in Arctic oilfields. Long-term monitoring of fish catches using four fyke nets allowed assessment of changes in catch rates during a 2014 seismic survey in Prudhoe Bay, Alaska. Fyke net locations were instrumented with both conventional hydrophones and vector sensors. Catch rates were generally within the range of those found in 27 previous sampling seasons. The effect of air guns on eight species was assessed using a modified Before-After/Control-Impact analysis, with historical data and 2014 data as the Before-After components of the analysis and days without and with air gun activity as the Control-Impact components. Results showed significant changes associated with air guns in catch rates at one or more nets at p < 0.1 for all eight species and at p < 0.05 for seven of the eight. Changes included both increased and decreased catch rates, perhaps reflecting displacement of fish in response to air gun sounds throughout the study area. Measured sound pressure levels associated with air gun pulses were low and usually undetectable close to the fyke nets, reflecting the loss of low frequencies in shallow water (~1.5 m). Attempts to measure particle velocities failed when wind-driven surface waves overwhelmed vector sensors. However, fish responses may have been related to changes in particle motion associated with air gun sounds.

Resilience of a tropical sport fish population to a severe cold event varies across five estuaries in southern Florida

AbstractFor species that are closely managed, understanding population resilience to environmental and anthropogenic disturbances (i.e., recovery trajectories across broad spatial areas) can guide which suite of management actions are available to mitigate any impacts. During January 2010, an extreme cold event in south Florida caused widespread mortality of common snook, Centropomus undecimalis, a popular sport fish. Interpretation of trends using fishery‐independent monitoring data in five south Florida estuaries showed that changes in catch rates of adult snook (>500 mm standard length) varied between no effects postevent to large effects and 4‐yr recoveries. The reasons for the variation across estuaries are unknown, but are likely related to differences in estuary geomorphology and habitat availability (e.g., extent of deep rivers and canals) and differences in the proportions of behavior contingents (i.e., segments of the population that use divergent movement tactics) that place snook in different areas of the estuary during winter. Emerging awareness of the presence of behavior contingents, identification of overwintering sites, and improvements of abundance indices in remote nursery habitats should provide a better understanding of population resilience to disturbance events for snook. Given that changes in the frequency of short‐lived, severe cold events are currently unknown, the findings and management actions described here for a tropical species living at the edge of its distribution should be useful to scientists forecasting the effects of climate change.

Benefit transfer with limited data: An application to recreational fishing losses from surface mining

The challenges of applying benefit transfer models to policy sites are often underestimated. Analysts commonly need to estimate site-specific effects for areas that lack data on the number of people who use the resource, intensity of use, and other relevant variables. Here, we address issues of applying transfer functions to sites that have sparse or missing data. We present options for estimating data to apply meta-regression models (MRMs) in ways that are scale-appropriate and sensitive to local conditions. Using a case study of the potential lost welfare to freshwater anglers as a result of mountain top coal mining within West Virginia, we integrate: 1) an empirical ecological model of fish community changes; 2) an MRM that relates changes in catch rates to changes in anglers' utility; and 3) a spatial participation analysis that maps trip distribution using multiple survey datasets. We evaluate two scenarios: partial (20%) and full use of existing mine permits. Our conservative estimates of annual welfare loss are $120,500 for the partial scenario and $627,800 for the full scenario, due to changes in recreational fishing catches. These results are sensitive to catch rate assumptions and socio-demographic characteristics that varied widely depending on the spatial scale of measurement.

Keeping Food on the Table: Human Responses and Changing Coastal Fisheries in Solomon Islands.

Globally the majority of commercial fisheries have experienced dramatic declines in stock and catch. Likewise, projections for many subsistence fisheries in the tropics indicate a dramatic decline is looming in the coming decades. In the Pacific Islands coastal fisheries provide basic subsistence needs for millions of people. A decline in fish catch would therefore have profound impacts on the health and livelihoods of these coastal communities. Given the decrease in local catch rates reported for many coastal communities in the Pacific, it is important to understand if fishers have responded to ecological change (either by expanding their fishing range and/or increasing their fishing effort), and if so, to evaluate the costs or benefits of these responses. We compare data from fish catches in 1995 and 2011 from a rural coastal community in Solomon Islands to examine the potentially changing coastal reef fishery at these time points. In particular we found changes in preferred fishing locations, fishing methodology and catch composition between these data sets. The results indicate that despite changes in catch rates (catch per unit effort) between data collected in 2011 and 16 years previously, the study community was able to increase gross catches through visiting fishing sites further away, diversifying fishing methods and targeting pelagic species through trolling. Such insight into local-scale responses to changing resources and/or fisheries development will help scientists and policy makers throughout the Pacific region in managing the region’s fisheries in the future.

허베이 스피리트호의 기름유출에 따른 바다유어낚시어선 이용객의 경제적 손실평가연구

This paper aims to evaluate the indirect economic damages to anglers of the marine recreational charter caused by marine pollution associated with the Herbei Spirit vessel, which spilled 12,547 kl of crude oil in Taean coastal areas in December 2007. In order to evaluate the indirect cost to anglers of the charter fishing, consumer surplus for charter fishing is estimated using a Poisson model (PM), a negative binomial model (NBM), a truncated Poisson model (TPM), and a truncated negative binomial model (TNBM), which account for the characteristics of count data (non-negative discrete data), for individual travel cost method (ITCM). Because of over-dispersion problem in PM and TPM, NBM and TNBM are considered to be more appropriate statistically. All parameters such as income, fishing careers, travel cost and catch that are estimated are statistically significant and theoretically valid. Based on TNBM results, consumer surplus per trip and per person was estimated to be 277 thousand won, total consumer surplus per person and per year about 2.3 million won, and the marginal effect of consumer surplus on % changes in catch rate is about 33 thousand won. The consumer surplus was converted into total indirect economic damages for aggregation which are evaluated to be 125 billion won, reflecting the number of anglers and damage rate.

Shifts in the estuarine demersal fish community after a fishery closure in Puget Sound, Washington

Puget Sound is one of the largest and most ecologically significant estuaries in the United States, but the status and trends of many of its biological components are not well known. We analyzed a 21-year time series of data from standardized bottom trawl sampling at a single study area to provide the first assessment of population trends of Puget Sound groundfishes after the closure of bottom trawl fisheries. The expected increase in abundance was observed for only 3 of 14 species after this closure, and catch rates of most (10) of the abundant species declined through time. Many of these changes were stepwise (abrupt) rather than gradual, and many stocks exhibited changes in catch rate during the 3-year period from 1997 through 2000. No detectable change was recorded for either temperature or surface salinity over the entire sampling period. The abrupt density reductions that were observed likely do not reflect changes in demographic rates but may instead represent distributional shifts within Puget Sound.

Factors influencing the distribution of Kona crabs Ranina ranina (Brachyura: Raninidae) catch rates in the Main Hawaiian Islands

A generalized linear model and commercial catch report data were used to describe spatial and temporal patterns in Kona crab, Ranina ranina Linnaeus, 1758, catch rates in the Main Hawaiian Islands. Three alternative hypotheses regarding factors influencing the temporal and spatial distribution of Kona crabs were evaluated using multi-model inference. Broad-scale island effects explain the spatial distribution of catch rates better than the finer-scale factors of depth and swell exposure. Interdecadal declines in catch rates were noted for islands with high human density, while other islands had stable or increasing catch rates. The interdecadal changes in catch rates may be explained by changes in population abundance and management-induced changes in fishing patterns in the recent period. Kona crab behaviors associated with the reproductive cycle contribute to seasonal variations in observed catch rates.

Sounds from seismic air guns: gear- and species-specific effects on catch rates and fish distribution

Previous studies found that sounds generated by seismic air guns led to pronounced reductions in commercial catches from trawls and longlines and the displacement of fish from fishing grounds. In contradiction to these findings and fishermen’s concerns, we demonstrate here that gillnet catches were doubled for redfish ( Sebastes norvegicus ) and Greenland halibut ( Reinhardtius hippoglossoides ) during seismic shooting on a Norwegian fishing ground (86% and 132% increase, respectively, compared to preshooting levels). However, longline catch rates fell (16% for Greenland halibut, 25% for haddock ( Melanogrammus aeglefinus )). These contradictory results were explained by greater swimming activity versus lowered food search behaviour in fish exposed to air-gun sound emissions. Changes in catch rates of all species studied (including saithe (i.e., pollock, Pollachius virens ) and ling ( Molva molva )) were found, indicating that these species all responded to air-gun sounds. Except for saithe, acoustic mapping of fish abundance did not suggest displacement from fishing grounds. Less intense sound exposure compared with previous studies and strong habitat preference in some species may explain this finding.

Evaluating empirical decision rules for southern rock lobster fisheries: A South Australian example

The fishery for rock lobsters in South Australia's southern zone has been in decline for several years. Previous harvest strategies included limit reference points, but did not specify explicit total allowable commercial catches (TACCs) when these reference points were breached. Two alternative catch-rate-based decision rules for setting TACCs for this fishery were proposed by stakeholder groups, including government scientists and the fishing industry. The two decision rules (“discrete” and “linear”) set TACCs based on changes in catch-rates, with the general aim of achieving a constant exploitation rate. The two rules differed in terms of how TACCs are changed given changes in catch-rate. Management strategy evaluation is used to evaluate these decision rules. The “discrete” rule leads to greater variation in catches, but to somewhat lower risks. However, unlike the linear rule, the discrete rule cannot reduce [or increase] catches markedly. Based on the trade-offs between risk and catch, as well as the need for buy-in of impacted stakeholders, the discrete rule was selected as the basis for setting TACCs for the southern rock lobster fishery for the next 3–5 years.

Using catch rate data for simple cost-effective quota setting in the Australian spanner crab (Ranina ranina) fishery

Abstract O'Neill, M. F., Campbell, A. B., Brown, I. W., and Johnstone, R. 2010. Using catch rate data for simple cost-effective quota setting in the Australian spanner crab (Ranina ranina) fishery. – ICES Journal of Marine Science, 67: 1538–1552. For many fisheries, there is a need to develop appropriate indicators, methodologies, and rules for sustainably harvesting marine resources. Complexities of scientific and financial factors often prevent addressing these, but new methodologies offer significant improvements on current and historical approaches. The Australian spanner crab fishery is used to demonstrate this. Between 1999 and 2006, an empirical management procedure using linear regression of fishery catch rates was used to set the annual total allowable catch (quota). A 6-year increasing trend in catch rates revealed shortcomings in the methodology, with a 68% increase in quota calculated for the 2007 fishing year. This large quota increase was prevented by management decision rules. A revised empirical management procedure was developed subsequently, and it achieved a better balance between responsiveness and stability. Simulations identified precautionary harvest and catch rate baselines to set quotas that ensured sustainable crab biomass and favourable performance for management and industry. The management procedure was simple to follow, cost-effective, robust to strong trends and changes in catch rates, and adaptable for use in many fisheries. Application of such “tried-and-tested” empirical systems will allow improved management of both data-limited and data-rich fisheries.

The value of recreational fishing in the Great Barrier Reef, Australia: A pooled revealed preference and contingent behaviour model

Given the focus on protecting natural assets in the Great Barrier Reef Marine Park in Australia, it is important for managers and policy makers to understand the value of recreational fishing in the area, and how changes in management may affect those recreational values. Travel cost methods were used to estimate the value of recreational fishing in the Capricorn Coast in Central Queensland using data from on-site surveys conducted at boat ramps. The study also uses contingent behaviour models to estimate the change in the value of recreational fishing as conditions vary. Results indicate that there are high values associated with recreational fishing activity along the Capricorn Coast, and that the demand for recreational fishing is inelastic and that values are relatively insensitive to changes in catch rates.