Commercial Catch Per Unit Effort Research Articles

First Maximum Sustainable Yield advice for the Nephrops norvegicus stocks of the Northwest Iberian coast using stochastic Surplus Production model in Continuous Time (SPiCT)

The assessment of the status of fisheries resources is pivotal due to the importance of marine resources in global food security and to halt the ongoing decline in marine biodiversity. Norway lobster (Nephrops norvegicus) is one of the most valuable resources in the Northeast Atlantic. However, overfishing has caused the decline of several Nephrops stocks over the last decades, particularly in the Nephrops Functional Units (FUs) 25 (NW Spain), 26-27 (NW Spain and North Portugal) and 31 (Cantabrian Sea, North Spain). Since 2003, the information provided by the very low level of landings and fishing effort of these three stocks was insufficient to carry out an adequate analytical assessment, so the base of the assessment has been the trends from commercial catch per unit effort (CPUE). The objective of this study was to carry out the first assessment of these three stocks with an analytical MSY-based model. A review of the available data was made and the stochastic Surplus Production Model in Continuous Time (SPiCT) was fitted for each FU. The results indicate an extremely low biomass for FUs 25 and 26-27 since the mid-nineties well below the reference points. For FU 31, on the other hand, estimated biomass is larger. Our findings also identified long-term temporal and spatial changes in the population dynamic of Nephrops in the Northwest Iberian coast. The results were compare with those obtained in the same stocks with other data-limited methods. Also the role of abiotic factors on the observed dynamic of the stocks was explored. The results of this study are not only relevant for the sustainable exploitation of Norway lobster stocks off the Northwest Iberian coast but provide valuable insights into the suitability and limitations of production models for the assessment of crustacean stocks in general.

Detection and quantification of differences in catch rates among research vessel gears and commercial vessels

Commercial fishing vessels can be a cost-effective alternative to research vessels for performing towed gear fishery-independent surveys, if catch rates are comparable among commercial vessels and with research vessels. A parallel fishing experiment was conducted off the coast of Wales, United Kingdom, to compare the king scallop (Pecten maximus) catch rates of three commercial vessels using commercial dredges and a research vessel using two types of scientifically modified dredges. The scientific dredges are currently used in the fishery-independent survey of local scallop populations. Size-structured scallop catch-per-unit-effort (CPUE) was compared among vessel-gear combinations. Two similarly sized commercial vessels had generally similar CPUEs, however there were some significant differences with scallop size. A smaller commercial vessel had significantly lower CPUEs for a broad range of scallop sizes. The research vessel dredges had significantly higher CPUE for smaller scallops than the commercial vessels. Vessel size is likely to be driving the differences among commercial vessels and belly ring size is likely to be driving differences among research and commercial dredges. These findings highlight commercial vessel CPUE should not be assumed the same, whilst also showing that vessel size may be the best indicator of catch rate similarity. These results also highlight that changing the fishery-independent vessel and gear to the commercial options trialled here would result in a considerable loss of information about the smaller scallops in the population. These findings will be of interest to fishery scientists or managers using multiple vessels, or considering a change of vessels, for fishery-independent surveys.

Mapping and Assessing Commercial Fisheries Services in the Lithuanian Part of the Curonian Lagoon

The spatial distribution of biomass of main commercial fish species was mapped to estimate the supply of a provisioning fishery service in the Curonian lagoon. Catch per unit effort (CPUE) was used as a proxy to estimate the efficiency of commercial fishing and, subsequently, the potential biomass of fishes. The relationship between distinctive characteristics of the fishing areas and corresponding commercial catches and CPUE was analyzed using multivariate analysis. The total catch values and CPUE used in the analyses were derived from the official commercial fishery records. RDE analysis was used to assess the variation of both catch and CPUE of commercial fish species, while the percentages of bottom sediment type coverage, average depth, annual salinity, and water residence time in each of the fishing squares were used as explanatory variables. This distance e-based redundancy analysis allowed for the use of non-Euclidean dissimilarity indices. Fisheries data spatial distribution map indicated the lack of coherence between the spatial patterns of commercial catches and CPUE distribution in the northern part of the lagoon. Highest CPUE values were estimated in the central-eastern part of the lagoon as compared to the western part of the lagoon where CPUE values were substantially lower. Both total catch and CPUE appeared not to be related to the type of bottom habitats statistically while being spatially correlated in-between. However, the impact of salinity and water residence time calculated using the 3D hydraulic circulation model on the distribution of both CPUE and commercial catches was statistically significant.

Precipitous Declines in Northern Gulf of Mexico Invasive Lionfish Populations Following the Emergence of an Ulcerative Skin Disease

Invasive Indo-Pacific lionfish Pterois volitans/miles have become well-established in many western Atlantic marine habitats and regions. However, high densities and low genetic diversity could make their populations susceptible to disease. We examined changes in northern Gulf of Mexico (nGOM) lionfish populations following the emergence of an ulcerative skin disease in August 2017, when estimated disease prevalence was as high as 40%. Ulcerated female lionfish had 9% lower relative condition compared to non-ulcerated females. Changes in lionfish size composition indicated a potential recruitment failure in early summer 2018, when the proportion of new recruits declined by >80%. Remotely operated vehicle surveys during 2016–2018 indicated lionfish population density declined in 2018 by 75% on natural reefs. The strongest declines (77–79%) in lionfish density were on high-density (>25 lionfish per 100 m2) artificial reefs, which declined to similar levels as low-density (<15 lionfish per 100 m2) artificial reefs that had prior lionfish removals. Fisheries-dependent sampling indicated lionfish commercial spearfishing landings, commercial catch per unit effort (CPUE), and lionfish tournament CPUE also declined approximately 50% in 2018. Collectively, these results provide correlative evidence for density-dependent epizootic population control, have implications for managing lionfish and impacted native species, and improve our understanding of biological invasions.

Data-moderate assessments of Cape monkfish Lophius vomerinus and west coast sole Austroglossus microlepis in Namibian waters

There is global interest in providing scientific advice on optimal harvesting of all commercially exploited fish stocks. Nevertheless, many commercially important stocks lack analytical assessments. Therefore, we evaluate a data-moderate stock assessment method: the stochastic surplus production model in continuous time (SPiCT). The method was applied to two Namibian stocks: (i) the data-rich Cape monkfish Lophius vomerinus, where results are compared to a new data-rich assessment using a state–space assessment model (SAM); and (ii) the data-moderate west coast sole Austroglossus microlepis, which is an important bycatch species in the Cape monkfish fishery, but currently unassessed. The information available to the data-moderate assessment is total commercial catch, commercial catch per unit effort (CPUE), and survey CPUE. SPiCT and SAM gave largely consistent estimates of relative fishing mortality (F/FMSY) and relative exploitable biomass (B/BMSY) for the Cape monkfish stock, although with some discrepancies. Differences in the biomass estimates between the two assessments suggest that further investigation is required to understand the cause, and that some caution is necessary when considering the biomass of the stock. SPiCT shows that the west coast sole may be overexploited, although the confidence bounds were too wide for a firm conclusion. Similarity in the estimates of F/FMSY for Cape monkfish in recent years, using SPiCT relative to SAM, likewise indicates the suitability of SPiCT for managing west coast sole.

Glass eel (Anguilla anguilla) recruitment to the river Lis: Ingress dynamics in relation to oceanographic processes in the western Iberian margin and shelf

AbstractTo provide new information on the ingress dynamics of glass eels at the Portuguese coast, the study analyzes catch per unit effort (CPUE) data from river Lis, biometric data from recruits in basins of western Portugal and meteo‐oceanographic data from the Iberian margin and shelf. Biometric data of glass eels in western Portugal are congruent with the latitudinal size gradient of leptocephali in oceanic surveys and show clear seasonality, with longest and heaviest individuals arriving from October to December. Generalized additive models fitted to CPUEs from two experimental fishing periods (1996–1997 and 2013–2014) show that availability of glass eels to the sampling gear was inversely related to lunar phase and sea wave height. CPUE was lowest from May to September, increased towards the end of the year and peaked in February–March, when recruits were almost 40% lighter than autumn arrivals. Commercial CPUE during the 1989–1990 fishing season was significantly higher than experimental fishing data in 1996–1997. Higher variance and smaller sample size in 2013–2014 prevent conclusive interdecadal comparisons. Finally, CPUE was significantly higher during the prevalence of northward current flow off western Portugal and during strong cross‐shelf westerly winds. Findings support the suggestion that eel recruitment in Portugal occurs mainly by leptocephali travelling along the Azores Current, deflected northwards through the Iberian Poleward Current, with river ingress, and possibly oceanic metamorphosis, modulated by seasonal dynamics in coastal hydrology and shelf/upper margin oceanography.

Seabird diet predicts following-season commercial catch of Gulf of California Pacific Sardine and Northern Anchovy

The highly productive Gulf of California exhibits high biodiversity and an abundance of small pelagic, schooling fishes, important both to the ecosystem and to fisheries. These fishes show wide fluctuations in abundance due to oceanographic–atmospheric phenomena such as El Niño-Southern Oscillation, constituting a problem for effective fisheries management. In this work we propose several parameters in the diet of three seabird species as useful predictors of the eventual commercial catch per unit effort (CPUE) of Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax) in the Midriff Island Region of the Gulf of California. We found that seabirds are sensitive to fluctuations in the abundances of these fishes, their proportions in the diet becoming suitable predictors of future commercial CPUE. The precision of our prediction is high because the birds feed on pre-recruit fish, and the time between the sampling of the diets and the initiation of the fishing season is short, minimizing stochastic effects on recruitment and subsequent abundance due to environmental fluctuations.

How reliable are the abundance indices derived from commercial catch–effort standardization?

Commercial catch-per-unit-effort (CPUE) data are often standardized to construct indices of stock abundance. The value of such standardization lies in the improvement in the proportionality between the derived index and true abundance. Using the Torres Strait rock lobster ( Panulirus ornatus ) fishery in Australia as an example, we first standardized the commercial CPUE data using a generalized linear model (GLM) and then fitted observation error models to the resulting abundance indices and independent abundance data (as estimated by research diver surveys) to examine the proportionality. While the GLM standardization greatly improved proportionality in comparison with the nonstandardized commercial catch rates, it could produce biased results if the model did not explicitly incorporate variables that had caused changes in fishing efficiency. As most catch–effort standardizations do not model the fishing power component simultaneously, this result may serve as a warning to the potential bias in stock abundance indices extracted from GLMs that are underfitted.

Estuarine gillnet fishery catch rates decline during drought in eastern Australia

Commercial catch-per-unit-effort (CPUE) data from nine estuaries were related to hydrological variation in eastern Australia. Relationships between drought declaration, rainfall, freshwater flow and fisheries catch rates were assessed from 1997 to 2007. Estuaries varied from 0.5 to 2.0 × 10 6 ML of mean freshwater inflow per annum. Monthly CPUE data from gillnetting were used to infer the abundance of yellowfin bream ( Acanthropagrus australis), dusky flathead ( Platycephalus fuscus), luderick ( Girella tricuspidata), sand whiting ( Sillago ciliata) and sea mullet ( Mugil cephalus). CPUE for all species examined, except yellowfin bream, increased in proportion to freshwater flow and decreased during periods of drought. Freshwater flow may affect CPUE by stimulating migration and schooling due to salinity fluctuations altering habitat availability. Minimum and maximum flows were important determinants of CPUE. Freshwater flow per se may not be as important in influencing CPUE as extremes in the hydrological continuum. Seasonal flows were consistently the most important aspect of the flow regime that explained the highest proportion of variability in CPUE. Seasonal freshwater pulses proximate to critical reproductive periods may influence catchability by triggering seaward spawning migrations in estuarine-dependent fish.

Investigating variability in catch rates of halibut (Hippoglossus stenolepis) in the Pribilof Islands: Is temperature important?

Abstract From 2002 to 2004, a study was conducted to test the hypothesis that commercial catch per unit effort (CPUE) of Pacific halibut (Hippoglossus stenolepis) in the Pribilof Islands local fishery varies on intra-annual (weeks–months) and inter-annual (among fishing seasons) time scales due to (a) variation in seasonal migration timing, (b) temperature-dependent habitat preference, or (c) average local abundance governed by late spring hydrographic conditions. Changes in CPUE over the progression of three fishing seasons were examined for evidence of seasonal migration signals. Relationships between catch and water temperature were examined by deploying temperature recorders from local commercial vessels and correlating the observations with vessel-standardized CPUE intra- and inter-annually. Temperature data were obtained from 735-longline sets; simultaneous depth data were collected from a subset of 412 of those deployments. Annual temperature data clearly demonstrated seasonal warming trends, and temperature was negatively correlated with depth. Warmest conditions were observed in 2003: maximum temperatures of ∼6 °C were observed in early June and increased to ∼10 °C in early September. Conditions in 2002 and 2004 were similar to one another and on average about 1 °C cooler than in 2003, warming from ∼5 °C in June to ∼9.5 °C in September. No intra-annual trend in CPUE was apparent. A relationship was not detected between temperature and vessel-standardized CPUE within years, whether CPUE was compared to absolute temperature or the difference between observed temperature and daily-predicted maximum. These results suggest that halibut do not respond strongly to temperatures within the observed range, nor was there evidence that the fishery was influenced by seasonal movement patterns. These conclusions are supported by concurrent archival tagging that suggests the Pribilof fishery may be too short to capture seasonal migration periods; summer local abundance is likely established prior to commencement of the fishery. Temperatures observed by the fleet were also within the known thermal tolerances of Pacific halibut. Inter-annually, cumulative fleet-wide CPUE and total catch were associated with coolest annual mean temperature. A relationship might exist between annual CPUE and mean temperature, but the available time series is too short to draw conclusions in this regard. While there was no trend in CPUE from June through August or across temperatures ranging from 5 to 10 °C, the results may be valuable in refining hypotheses and focusing future effort. Additional research should seek to examine catch trends earlier and later in the year, as well as at higher and lower temperatures, perhaps at the edges of the species's geographic range or during years characterized by anomalous hydrographic conditions.

Movement of Walleyes in Lakes Erie and St. Clair Inferred from Tag Return and Fisheries Data

AbstractLake Erie walleyes Sander vitreus support important fisheries and have been managed as one stock, although preliminary tag return and genetic analyses suggest the presence of multiple stocks that migrate among basins within Lake Erie and into other portions of the Great Lakes. We examined temporal and spatial movement and abundance patterns of walleye stocks in the three basins of Lake Erie and in Lake St. Clair with the use of tag return and sport and commercial catch‐per‐unit effort (CPUE) data from 1990 to 2001. Based on summer tag returns, western basin walleyes migrated to the central and eastern basins of Lake Erie and to Lake St. Clair and southern Lake Huron, while fish in the central and eastern basins of Lake Erie and in Lake St. Clair were primarily caught within the basins where they were tagged. Seasonal changes in sport and commercial effort and CPUE in Lake Erie confirmed the walleye movements suggested by tag return data. Walleyes tagged in the western basin but recaptured in the central or eastern basin of Lake Erie were generally larger (or older) than those recaptured in the western basin of Lake Erie or in Lake St. Clair. Within spawning stocks, female walleyes had wider ranges of movement than males and there was considerable variation in movement direction, minimum distance moved (mean distance between tagging sites and recapture locations), and mean length among individual spawning stocks. Summer temperatures in the western basin often exceeded the optimal temperature (20–23°C) for growth of large walleyes, and the migration of western basin walleyes might represent a size‐dependent response to warm summer temperatures. Cooler temperatures and abundant soft‐rayed fish probably contributed to an energetically favorable foraging habitat in the central and eastern basins that attracted large walleyes during summer.

Catchability and the spatial distribution of fishing vessels

A central problem when using commercial catch per unit effort (CPUE) as an index of fish stock abundance is that fishing vessels search for concentrations of fish. For a given stock abundance, CPUE may become high if the vessels succeed in finding patches of fish and low if the vessels distribute their catching operations more randomly. In this work, the relationship between catchability and two measures of the degree of spatial concentration of a trawl fleet (the fleet's spatial extent and the fleet's degree of spatial patchiness) is investigated for four different fish stocks. The catchability of northeast Arctic cod (Gadus morhua) is strongly related to the fleet's degree of spatial concentration, but the relationship is weaker for northeast Arctic haddock (Melanogrammus aeglefinus), and no relationships appear for two saithe (Pollachius virens) stocks. Our findings suggest that adjusting CPUE with a measure of the fleet's average degree of concentration relates CPUE more strongly with abundance for migratory stocks.

A Biomass Index for Northern Shrimp (Pandalus borealis) in Davis Strait Based on Multiplicative Modelling of Commercial Catch-per-unit-effor Data (1976-97)

Four biomass indices for the northern shrimp (Pandalus borealis) stock in Davis Strait, derived from commercial catch-per-unit-effort (CPUE) data, were analysed by multiple regression to construct a single time series with the ultimate goal of tracking trends in stock biomass during the period 1976 to 1997. Indices from the offshore fisheries have been used previously in stock assessments while an index derived from logbook data for small inshore vessels operating around Disko Island has not been presented previously. The analysis used multiplicative models and linked catch rate to vessel fishing power, temporal and spatial availability and overall annual biomass density. In two of the indices, the temporal (MONTH) and spatial (AREA) effects were modelled as interaction terms. Other second order effects were treated as random error. The AREA*MONTH interaction term corresponds to an annual migration or behavioural pattern. The procedure corrects for increases in technological efficiency over the 22-year period due to fleet renewal but changes in the efficiency of individual vessels were not accounted for. The four indices were combined, weighted by the area of the total fishing grounds each index represented. The combined index was indicative of the biomass density for shrimp greater than about 17 mm in carapace length. During the 1976–88 period, the index was higher than from 1989 onwards. The combined index showed agreement with research survey biomass estimates but the contrast in the data was low during the period of comparison (1988–97). The combined CPUE index was applied to the total catches to derive estimates of total standardized effort. This effort index increased substantially in the late-1980s.

Dynamics and Species Interactions in the Commercial Fishery of the Red lakes, Minnesota

The Red Lakes, Minnesota, have supported a commercial fishery for walleye (Stizostedion vitreum vitreum) and yellow perch (Perca flavescens) since 1917. Since 1972, harvests indicate increased variance in recruitment of percids and an increase in biomass of freshwater drum (Aplodinotus grunniens). We subjected commercial catch-per-unit-effort (CPUE) records of walleye, yellow perch, and animal feed (composed primarily of drum) to spectral analysis. Estimated power spectra displayed peaks at 8.5, 10, and 17 yr for walleye, yellow perch, and animal feed, respectively. Walleye and yellow perch CPUE time series were significantly coherent at periods ranging from 5to 10 yr, confirming the predator–prey relationship and common recruitment patterns of these two species. Interpretation of coherency between drum and the two percid species required knowledge of the age distribution of freshwater drum. The apparent exponential increase in drum biomass as indicated by commercial CPUE is primarily due to strong year classes in 1955, 1970, and 1983. While drum recruitment and growth are consistent with the periodicity in the autospectrum, we find little evidence from coherencies that drum recruitment is related to the dynamics of wlleye or perch populations.