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Walleyes Sander vitreus are an important sport fish found throughout the northern Great Plains of North America. Periods of increased precipitation across the Great Plains can result in new or expanded lakes that contain unexploited fish populations. We assessed angler exploitation of a previously unexploited walleye population to estimate exploitation rates, subsequent changes in walleye abundance, and changes in angler behavior. This research provides an opportunity to add to the limited body of information concerning walleye exploitation and exploitation of unexploited populations. Hazeldon Lake, South Dakota contained an unexploited walleye population and was opened to angling on 15 July 2006. Initial exploitation was high, estimates exceeded 16% after two days and 75% after 16 days. Anglers harvested an estimated 6868 walleyes during 15 July - 31 August 2006; this harvest represented 79% of the pre-opener population estimate of 8661. The 2007 spring population estimate was 2436 fish and represented a 72% decline from the 2006 estimate. Gill net catch per unit effort (CPUE) averaged 30.0 fish net−1 prior to fishing in 2006; the 2007 CPUE was 76% lower at 7.2 fish net−1. A lack of recruitment resulted in no substantial increases in relative abundance from 2007-2017. Fishing pressure was high when the lake first opened to fishing. However, the number of anglers and exploitation rates declined once walleye catch and harvest rates dropped off. Our results suggest that walleye populations in new or expanded waters located in the northern Great Plains can be extremely vulnerable to angling but when catch rates drop off few anglers will continue to fish a given water; instead moving to other waters potentially having higher walleye catch rates. [ABSTRACT FROM AUTHOR]

Catch rates reported by fishers are commonly used to understand the status of a fishery, but the reliability of fisher-reported data is affected by how they recall such information. Recalling catch may be influenced by the choice of reporting time period. Using interview data from fishers in Thailand, we investigated (1) how the time period for which fishers report their catch rates (e.g., per day or month) correlates with annual catch estimates and (2) the potential of recall bias when fishers reported multiple catch rates. We found that the annual catch estimates of fishers who reported on a shorter time period (haul, day) were significantly higher than those reported on a longer time period (month, year). This trend held true when individual fishers reported over multiple time periods, suggesting recall bias. By comparing fisher reports with external data sets, we identified that the mean across all reports was most similar to other data sources, rather than any time period. Our research has strong implications in using fishers' knowledge for fisheries management. [ABSTRACT FROM AUTHOR]

This study investigated the efficiency of a sieve‐panel concept, intended to separate bycatch species from Nephrops (Norway lobster) in a trawl gear via mechanical and behavioural means. Four different designs of varying panel mesh size or inclination were tested in experimental fishing. For each design, the length‐dependent sieving efficiency, defined as the fraction of Nephrops or fish passing through the panel to the lower codend, was estimated. The sieving efficiency for Nephrops increased from ~17% to ~71% as mesh size increased, and decreased with increasing carapace length, but did so less as panel inclination and mesh size increased. The sieving efficiency for roundfish was low, as intended, while the efficiency for flatfish decreased with fish size. Although results are promising, the sieving efficiency for the largest, most valuable Nephrops remained too low. Therefore, further improvements are necessary before the concept is acceptable to the commercial fishing fleet. [ABSTRACT FROM AUTHOR]

A Sort‐X grid device with four different bar‐spacing grids (25, 30, 40 and 50 mm) was tested in the Gulf of Cádiz (GoC) on‐board commercial trawlers. A total of 83 fish, five crustacean and nine cephalopods species were sampled in 282 hauls. Most of the target and commercial bycatch species were sorted out by the grid with the exception of hake. Merluccius merluccius (L.). Additionally, common pandora, Pagellus erythrinus (L.), sardine, Sardina pilchardus (Walbaum), octopus, Octopus vulgaris Lamark, and cuttlefish, Sepia officinalis L., also showed a sizeable retention for some of the grid bar spacing. Statistical modelling of selectivity at length for hake found influence of depth on the selection parameters. Lengths at 50% retention for hake were estimated to be 27.4, 30.3, 36.3 and 42.3 cm TL for 25–50 mm bar spacing, respectively, all above the minimum conservation reference size (MCRS) in the GoC. The probability of hake contacting the grid was estimated as 0.95. Overall, although the selective device showed a good performance for hake, it is not appropriate for improving the fishing pattern of a multi‐species trawl fishery such as that of the GoC. [ABSTRACT FROM AUTHOR]

We analyzed recreational and commercial catch records from 1980 to 2009 for the fishing blocks associated with the 5 southern offshore banks of the Southern California Bight (Cortes Bank, Tanner Bank, Northeast Bank, Cherry Ridge, and Garrett Ridge). Recreational fishers and divers targeted pelagic taxa (e.g., tunas and Yellowtail) but instead landed more benthic taxa (e.g., rockfishes, Ocean Whitefish, and California Sheephead). For the commercial fisheries, pelagics (Bluefin Tuna, Albacore, Skipjack, Yellowfin Tuna, Pacific Bonito, and Swordfish) were the most important taxa and represented a significant proportion (8%–27%) of the landings of these fishes in the bight. These fishes were caught primarily at Cortes and Tanner Banks, which together only represent 3.7% of the fishing grounds in the region. In addition, this proportion of catch of these critical species has been significantly increasing at the outer banks during this period. Based on their geography and physical oceanography, we propose that these offshore banks comprise a unique habitat for pelagic resources in the Southern California Bight. [ABSTRACT FROM AUTHOR]

To investigate the population dynamics of naturally recruited wild Japanese eels, fisheries data of wild individuals in Okayama Prefecture were investigated as a case study. Wild and stocked eels were discriminated using a recently developed method based on otolith stable isotopes. Of the 161 eels captured in freshwater areas where eels had been stocked, 98.1% were discriminated as stocked. In contrast, 82.8% of 128 eels captured in coastal areas where eels are not stocked were discriminated as wild. There was a significant decrease in longline and set-net catch per unit effort between 2003 and 2016 in the coastal areas where most eels were discriminated as wild, indicating ongoing depletion of wild Japanese eels in these waters. [ABSTRACT FROM AUTHOR]

Catch data, catch composition and fishing boat information were collected from 281 bottom trawlers and 70 fish carrier boats in Myeik Township, Tanintharyi Region, Myanmar in 2017. Meanwhile 50 fishermen were interviewed for data regarding trash fish price and its distribution. Trash fish statistics were also gathered from Myanmar's Department of Fisheries of Myeik Township, Tanintharyi Region. Information on trash fish utilization for fishmeal production was also gathered by interviewing four fishmeal factory managers in Myeik Township. In addition, other related information on Myanmar fisheries was reviewed. All information was used to describe the status of trash fish from the bottom trawl fishery and its utilization. Moreover, some management aspects were discussed. From the surveys, a catch composition of 39.16% trash fish, 60.34% marketable fish and 0.50% shrimp was found at the landing site. Information from fishermen showed that all bottom trawlers sold 100% of trash fish to local fishmeal plants, and trawlers provided 55% to 70% of the total trash fish for fishmeal production. Fishmeal produced during 2013 to 2017 was exported as follows: 42.06% to Thailand and 10.67% to Malaysia. Of the remainder, 43.76% was sold in Yangon for aquaculture and animal feed and 3.51% was sold to local animal farms. The data showed that trash fish are among the targeted species of the bottom trawl fishery in Myanmar. Although Department of Fisheries of Myanmar has implemented many measures to control overfishing and to conserve juvenile fishes, fishing for trash fish has not been reduced significantly, because price and demand incentives are high. This situation has led to an increase of new fishing boats in this region. To conserve juvenile fishes of economically important species from trawl fisheries in this area, alternative management approaches are needed. [ABSTRACT FROM AUTHOR]

A fisheries management model that identifies the economic optimal management of fisheries under the influence of nutrients is presented. The model starts from the idea that growth in fish biomass increases with increasing availability of nutrients owing to higher food availability up to a peak, after which growth falls due to eutrophication. The model is applied to Swedish and Danish cod fisheries in the Western Baltic Sea and identifies the welfare contribution of the fisheries, measured as the sum of resource rent and producer surplus. In 2010, the welfare contribution was −28% of the landing value. Maximizing the model with respect to effort alone and additionally over nitrogen concentration increases the contribution to 11% of the landing value in 2010. The analysis shows that the welfare effect of reducing fishing effort through management reforms is large, but that the effect of incorporating nitrogen in fisheries policy is small. [ABSTRACT FROM AUTHOR]

Recreational fishing is a major leisure activity in many European countries but social aspects of angling are still understudied. This study aimed to examine long-term social trends in recreational fishing. Data was obtained from annual angling reports collected by the Czech Fishing Union. Data from annual angling reports is based on data from individual angling logbooks collected from 238 fishing grounds over the course of 11 years in Prague and Central Bohemia, Czech Republic. It was discovered that the numbers of individual anglers and angling visits on fishing grounds have been increasing. An average angler visits higher diversity of fishing grounds but anglers keep on returning to individual fishing grounds less frequently. Frequency of angling guard controls on fishing grounds has been increasing as well. On the other hand, angling yield and catch have been decreasing. The number of anglers who take home at least one fish has been increasing but percentage of anglers who take home at least one fish has been decreasing. In conclusion, recreational fishing is on the rise but fish catch and yield are decreasing. [ABSTRACT FROM AUTHOR]

A study to assess the status of the large scale commercial fisheries operating in southern Lake Malawi was conducted using generalised linear modelling and Principles of Precautionary Approach. The generalised linear modelling analysis was used to standardise catch per unit of effort data from 1976 to 2009 and to determine the effects of fishing vessel characteristics such as engine size and hydro-acoustic devices on fish catch rates. The Precautionary Approach, through reference points like Bmax (reference point corresponding to period of relatively high fish catch rate), Bpa (reference point at which precautionary management action should be undertaken), Blim (limit reference point beyond which a fishery is considered seriously depleted) and Bcur (reference point corresponding to current fish catch rate), was used to assess the status of fish stocks using standardised fish catch rate which approximated fish biomass or stock size. Results of the assessment indicated that the current fish biomass level in all three categories, bottom pair trawl, stern bottom trawl and stern mid-water trawl fisheries, is well above Blim, but is 9-12% above Bpa, which is very close suggesting that the fishery is fully exploited and precautionary management measures are required. Suggested measures included introduction of fishing closed season for the large scale commercial fisheries which will be dependent on the biology of the most important target fish stocks, relocation or reduction of fishing effort in the current fishing grounds and intensification of patrols to reduce incidences of illegal, unreported and unregulated fishing activities. [ABSTRACT FROM AUTHOR]

Catch per unit effort (CPUE) is a widely used index of population abundance for informing stock assessments for the purpose of estimating population status and setting fishing policies. However, for CPUE to be an unbiased index, influences that are not related to population abundance (e.g., spatial variation in effort and temporal changes in gear efficiency) must be accounted for in analyses known as CPUE standardization. In longline fisheries, one important factor that can affect CPUE is the spacing between hooks (‘spacing effect’), which influences effective effort and has largely been ignored in previous analyses. Here, we use the Pacific halibut ( Hippoglossus stenolepis ) long-line fishery as a case study to explore the spacing effect. Both commercial and experimental (fishery-independent) data with hook spacing, and a survey-based CPUE series, are available for this fishery. It thus provides a unique opportunity to explore the effect of hook spacing and its effect on CPUE trends. We quantify this effect using non-parametric and parametric relationships inside a spatially-explicit (geospatial) CPUE standardization model for commercial data, and non-linear mixed-effects model for experimental data. We found a clear non-linear spacing effect (i.e., hooks were less effective the closer they were), but accounting for space had a larger effect on CPUE trends than accounting for hook spacing. For this stock, it is likely the effect of hook spacing on CPUE was minimal due to little variation in average hook spacing over time. Regardless, historical and future trends in hook spacing can have important effects on longline CPUE standardization, highlighting the value of collecting this information. Accounting for hook spacing effects in other fisheries may improve estimates of trends in relative abundance and lead to better management. [ABSTRACT FROM AUTHOR]

The Gulf of Mexico reef fish complex is socioeconomically important and is exploited by a vertical line fishery capable of high resolution spatial targeting. Indices of abundance derived from fishery dependent catch-per-unit-effort (CPUE) data are an important input to the assessment of these stocks. Traditionally, these indices have been derived from standardized logbook data, aggregated at a coarse spatial scale, and are limited to generating predictions for observed spatiotemporal strata. Understanding how CPUE is spatially distributed, however, can help identify range contractions and avoid hyperstability or hyperdepletion, both of which can mask the true population dynamics. Vessel monitoring systems (VMS) can provide complete, high-resolution distributions of CPUE used to create abundance indices. Here we compare two methods — spatial averaging of VMS-derived catch and effort data and the result of generalized linear models applied to logbook data for generating indices, to evaluate the use of VMS-derived abundance indices in assessments of reef fish stocks. This work suggests that in fisheries where targeting occurs at very fine spatial scales, abundance indices derived from high-resolution, spatiotemporally complete data may more accurately reflect the underlying dynamics of the stock. [ABSTRACT FROM AUTHOR]

To establish an estimation procedure for reliable catch amount of illegal, unreported and unregulated (IUU) fishing, light-gathering fishing operations in the northwestern Pacific were analyzed based on the Visible Infrared Imaging Radiometer Suite (VIIRS) day/night band (DNB) data provided by the Suomi National Polar Partnership (SNPP) satellite. The estimated fishing activities were compared with the navigation tracks of vessels obtained from the automatic identification system (AIS). As a model case, the fishing activities of Chinese fishing boats using fish aggregation lights outside the Japanese EEZ in the northwestern Pacific were analyzed from mid-June to early-September 2016. Integration analyses of VIIRS DNB data and AIS information provided reliable data for estimating the fishing activities of Chinese fishing boats and suggested the importance of estimating fish carrier ship movements. The total amount of the chub mackerel ( Scomber japonicus ) catch during this period was independently estimated from three angles: 1) the fishing capacity of the fishing boats, 2) the freezing capacity of refrigeration factory ships and 3) the fish hold capacity of the fish carrier ships, based on information obtained from interviews with Chinese fisheries companies. These estimates indicated that the total amount of mackerel catch by Chinese fisheries was more than 80% of the allowable biological catch (ABC) of Japan in this area in 2016. This suggests that Pacific high seas fishing has a significant impact on the future of fish abundance. Our proposed procedure raises the possibility of evaluating the fishing impact of some forms of IUU fisheries independently from conventional statistical reports. [ABSTRACT FROM AUTHOR]

The increase in anthropogenic CO 2 emissions over the last century has modified oceanic conditions, affecting marine ecosystems and the goods and services that they provide to society. Pacific Island countries and territories are highly vulnerable to these changes because of their strong dependence on ocean resources, high level of exposure to climate effects, and low adaptive capacity. Projections of mid-to-late 21st century changes in sea surface temperature (SST), dissolved oxygen, pH, and net primary productivity (NPP) were synthesized across the tropical Western Pacific under strong climate mitigation and business-as-usual scenarios. These projections were used to model impacts on marine biodiversity and potential fisheries catches. Results were consistent across three climate models, indicating that SST will rise by ≥ 3 °C, surface dissolved oxygen will decline by ≥ 0.01 ml L −1 , pH will drop by ≥ 0.3, and NPP will decrease by 0.5 g m −2 d −1 across much of the region by 2100 under the business-as-usual scenario. These changes were associated with rates of local species extinction of > 50% in many regions as fishes and invertebrates decreased in abundance or migrated to regions with conditions more suitable to their bio-climate envelope. Maximum potential catch (MCP) was projected to decrease by > 50% across many areas, with the largest impacts in the western Pacific warm pool. Climate change scenarios that included strong mitigation resulted in substantial reductions of MCP losses, with the area where MCP losses exceeded 50% reduced from 74.4% of the region under business-as-usual to 36.0% of the region under the strong mitigation scenario. [ABSTRACT FROM AUTHOR]

Scrapping programmes and individual transferable quotas (ITQs) are two management measures frequently used to reduce overcapacity in fisheries. These measures are often aimed at specific vessel segments targeting specific fish stocks. In this case, fishermen who scrap their vessels or sell their quotas may shift their fishing activities, possibly contributing to overcapacity in other fleets. The aim of this paper is to provide some insights on this issue based on a Swedish scrapping programme for trawlers targeting cod and Norwegian lobster and the introduction of an ITQ system for pelagic vessels introduced in 2008 and 2009. Individual-level data on fishing activities and income from other industries are used to examine how effort and catches have changed after 2009, and to what extent fishermen have left the fishing industry. The lesson learnt from the Swedish case is that fishermen tend to stay in the fishing sector, and this holds true for both participants in the scrapping programme and fishermen who sold their quota in the ITQ system. Therefore measures to reduce overcapacity in targeted fleets have increased fishing pressure and competition for quotas in the Swedish small-scale fleet. [ABSTRACT FROM AUTHOR]

Fishery-independent survey sampling programs frequently undergo changes in operational procedures, which have the capacity to alter the catchability coefficient, q . To preserve the continuity of the time series, changes in sampling protocol must be accounted for within the raw data. We used data from a long-standing shark longline survey as a case-study to demonstrate a method of estimating changing catch over variable soak times. Catches of longline sets with and without hook timers were modeled using generalized linear models (GLMs) to estimate catch conversion factors over varying soak times. Estimated conversion factors were used to correct the raw catch data, which were then analyzed with delta-lognormal GLMs to estimate indices of relative abundance. Uncertainty in conversion factor estimation was calculated via bootstrap resampling and propagated through to annual indices by correcting raw data using resampled conversion factors. Added variation introduced by implementation of correction factors was relatively small compared to the magnitude of the observation error of the resulting indices of relative abundance. In species where catch rate declined over soak time, the expected CPUE of shortened soak times increased relative to standard soak times. Contrarily, if catchability increased over soak time, expected CPUE decreased in shortened soak times. Thus, we showed that the predominant practice of treating each unit of sampling effort as equal in fixed, baited gear is not appropriate, and changes in soak time should be accounted for to preserve the longevity of the time series. [ABSTRACT FROM AUTHOR]

Conducting sample size analysis is important to ensure that sample sizes are adequate to meet objectives for precision but not so large that valuable resources are wasted. When simple survey designs are used, sample size analysis is straightforward. However, creel surveys often follow complex designs that can make sample size estimation difficult. The objectives of this study were to provide sample size estimators for commonly used creel survey designs and investigate sample size requirements to achieve varying levels of precision. For estimates of angling effort, the average sample size among fisheries required to achieve relative 95% confidence intervals of 40% (i.e., coefficient of variation of approximately 0.2) was 16 d (range = 7–40 d). To estimate mean catch rate with the same level of precision, 43 survey days (range = 8–95 d) were required when the daily catch rate estimator was used, and 11 d (range = 3–30 d) were required when the multi-day estimator was used. Fifty-five days (range = 14–89 d) and 57 d (range = 19–140 d) were required to estimate total catch with relative 95% confidence intervals of 40% when the daily and multi-day estimators were used, respectively. Although absolute precision will vary among fisheries, our results suggest that approximately 30 d of surveying may serve as a reasonable starting point for planning creel surveys when no prior information is available on expected sample variance, as relatively large increases in sample size beyond 30 d were needed to achieve relatively small increases in precision. Received February 14, 2017; accepted June 9, 2017 Published online August 4, 2017 [ABSTRACT FROM AUTHOR]

Forested headwater streams are dependent on their riparian zones for many critical goods and services. It is assumed that riparian disturbance affects stream food webs, but for some ecologically and economically important taxa like brook trout ( Salvelinus fontinalis), little research has been performed. This study found that intense but spatially limited riparian disturbance resulted in significant but context-dependent changes in the diets and condition of age-0 brook trout in three central Appalachian streams. Dietary shifts in two of the streams appeared to enable age-0 brook trout to maintain or increase condition following riparian tree removal. A significant relationship between fish condition and the importance of Ephemeroptera as prey was observed. The lack of dietary shift to energetically important ephemeropterans coincided with decreased fish condition within one stream previously identified to be mildly impacted by acid precipitation. The context within which riparian disturbance occurs plays an important role in determining the overall impact to age-0 brook trout and should be an important consideration in future regulatory and management decisions. [ABSTRACT FROM AUTHOR]

Fisheries bycatch can severely affect the population status of species with low resilience such as sharks. Bycatch monitoring is an important issue for the development of conservation and management plans for these species. The main objectives of this study were to quantify and model the spatiotemporal trend of bycatch for porbeagle shark ( Lamna nasus) in the Argentinean surimi trawl fleet to identify hotspots in the southwestern Atlantic Ocean. Using onboard observer data, we have demonstrated that L. nasus was usually caught as bycatch by the surimi trawl fleet operating in the southern limits of the southwestern Atlantic (51°S-57°S), representing an important part of the reported catch for the Atlantic Ocean. Delta and Tweedie models indicated that bycatch had a relatively stable trend, was concentrated in a limited region of the study area, and was associated with spatiotemporal, operational, environmental, and prey availability variables. The model with the best predictive capability used for the spatial delineation of hotspots for L. nasus bycatch showed that the areas located south of 54°12′S and over the continental shelf-break were critical for the porbeagle conservation and management strategies in the southwestern Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Although some stocks are being severely exploited by recreational fishing, estimating the biomass extracted (harvest, H ) by recreational fisheries is difficult, especially for marine recreational fisheries. One way to estimate H by recreational fisheries is to combine the fishing effort ( E ) with catch-per-unit-of-effort ( CPUE ) data. However, naively ignoring heterogeneity in E and CPUE may result in biased and imprecise estimates of H . We propose a framework to address three relevant heterogeneity levels: the spatial and temporal heterogeneity of recreational E , environmental effects on recreational CPUE , and the variability in angler skills (between-angler heterogeneity). Specifically, we combine (i) space-time model predictions of E (number of boats per km 2 ) on the day scale (i.e., fishing trips), (ii) environmentally driven model predictions of daily catch (number of squid per fishing trip), and (iii) off- and on-site surveys to account for angler heterogeneity. The precision of the H estimates was assessed using bootstrap confidence intervals. This framework was applied to the recreational fishery for the squid Loligo vulgaris at Palma Bay (Mallorca Island, western Mediterranean). The estimated effort was 15,750 angler-fishing trips (95% CI: 13,086 to 18,569), which yielded an annual harvest of 20.6 tons (95% CI: 16.9–24.5). This harvest was estimated to represent 34% of the total commercial landings in Mallorca, which highlights the importance of recreational harvesting and the need to account for recreational fisheries to improve squid stock management. The framework proposed here provides a promising tool for estimating H in other heterogeneous recreational fisheries and may be the first step toward assessing the actual impact of recreational fisheries on squid populations. [ABSTRACT FROM AUTHOR]

Research on the stock status and exploitation of the blue swimming crab Portunus pelagicus (Linnaeus 1758) in Lasongko Bay was conducted from April 2013 to March 2014. Blue swimming crabs were sampled monthly using gillnets and traps. Data on the number of fishermen and crab fishing gear were obtained via census and from secondary data and were analysed descriptively for every sampling period. Total catches of crabs were analysed using one-way ANOVA and t-test at p= 0.05. The status of crab stock was analysed using a Beverton--Holt model. The results showed that the number of fishing gear increased rapidly from 2006 to 2014, but was not proportional to the increases in crab catches, while the number of fishermen declined. The number of fishing gear and catch in 2006 and 2014 were 2,670 and 15,355 units and 44,194.56 kg and 66,926.6 kg, respectively. Daily crab catch were significantly different between the months. Crab stocks have been overfished and are currently considered critical, and thus the implementation of effective management is necessary. [ABSTRACT FROM AUTHOR]

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Recreational fishing effort was quantified at a 700 m 3 steel artificial reef (AR) off coastal Sydney with a shore-based camera (06:00–18:00) over a two-year period. Stratified random sampling was used to select days for analysis of fishing effort from digital images. Fishing effort estimates derived from the digital images were adjusted to account for visibility bias using information from a validation study. The levels of effort recorded in the first two seasons were low as the AR had been recently deployed and colonization of the AR by sessile organisms and fishes was still occurring. The effort intensity (fisher hours per square kilometer) at the Sydney AR was compared with three South Australian ARs and 14 estuarine fisheries in New South Wales (NSW) to provide context for the study. Effort intensity at the AR was found to be up to 12 times higher than that recorded from some estuarine fisheries in NSW. Conversely, the levels of effort intensity at two South Australian ARs were much higher compared to those at the Sydney AR site in both survey years. Effort intensity comparisons showed that the relative levels of usage at Australian ARs were higher than those recorded from estuarine fisheries. The Sydney AR provides diverse fishing opportunities that may be concentrated in a small area. Camera-based technologies can provide a solution for cost effective monitoring of AR sites, providing the accuracy of fishing effort information derived from camera images is validated. Our study has broad implications for other recreational ARs, including many future deployments planned for eastern Australia. [ABSTRACT FROM AUTHOR]

Gillnets are typically considered to be a commercial fishing gear yet their use by recreational fishers is permitted in several developed countries, often with few if any restrictions on the total number of users. Despite this there have been very few attempts to assess the impacts of recreational gillnet fisheries both in terms of harvest and implications for bycatch. Recreational gillnetting has a long history in Tasmania, Australia, and over the past two decades the fishery has been the focus of a number of management measures to improve fishing practices. In this study, the fishing activity of recreational gillnet license-holders was monitored for 12-months using a telephone-diary based panel survey. Catch, effort and fishing practices were compared with previous recreational fishing surveys and the commercial fishery. During 2010 an estimated 6600 recreational license-holders used gillnets, accounting for 25,712 (95%CI 22,142–28,901) net-days of effort and a total catch of 173,922 (95%CI 147,165–202,950) marine organisms, 35.5% of which were discarded. The recreational fishery is comprised of two main sub-fisheries, a mixed reef-fish fishery and a fishery for marine farm escapees. Four species, three representing key target species and one primarily a bycatch species, accounted for just over half of the total gillnet catch by number. The harvested component of the recreational gillnet catch was comparable to or exceeded commercial landings for the key species, highlighting the importance of taking account of the recreational fishery in stock assessments and species management. Despite an increase in the number of gillnet license-holders, recreational gillnet effort in Tasmania has halved since the late 1990s. This decline in effort appears to be linked to the greater regulation of fishing practices as well as reduced availability of two key target species, one of which has been classified as over-fished. Although recreational fishing practices have improved, the impacts on target and non-target species, including the incidental capture of seabirds and survival of bycatch, remain issues for concern. [ABSTRACT FROM AUTHOR]

Many political ecology debates hinge on the roles and outcomes of resource user regulation versus those arising from governance rules. Because of the difficulties of empirically testing theories of resource regulation, we evaluated the alternatives using a simulation modeling approach developed for East African coral reef fisheries where four scenarios of fisheries regulation on fish catch rates and resource ecology were evaluated. These scenarios were (1) a control simulation where fishing practices were held constant, (2) fishing that gradually incorporates fishers’ self-reported behavioral responses to declining resources, (3) rapid change where illegal gears were not allowed and effort was equally partitioned among the legal gears, and (4) gradual change where legal gears or exiting were adopted as yields decline. The model indicates that at moderate fishing effort (5 fishers/km 2 ), the gradual behavioral change scenarios two and four produced the highest per fisher yields and maintained the highest fish biomass compared to the other two strict-control options. At high fisher numbers (10 fishers/km 2 ), the rapid ban of illegal gear in scenario 3 had more similar ecological outcomes to gradual behavioral response scenarios 2 and 4. The model assumed no changes in behavior coming from outside the system or over longer periods of time that could potentially undermine or change the stated behavioral responses. The simulations show the difficulty of developing resource use regulations because of the complex interactions between numbers of fishers, behavioral responses, management decisions, and feedbacks to the resource. Nevertheless, the simulations indicate that at moderate fisher densities, governance strategies that allow resource users to respond to changing resources can produce better yield and resource outcomes than rigid control. Ecosystem models that do not incorporate fisher’s behavioral choices may overestimate their detrimental impacts. [ABSTRACT FROM AUTHOR]

We study the sensitivity of fishery management per-recruit harvest rates which may be part of a quantitative harvest strategy designed to achieve some objective for catch or population size. We use a local influence sensitivity analysis to derive equations that describe how these reference harvest rates are affected by perturbations to productivity processes. These equations give a basic theoretical understanding of sensitivity that can be used to predict what the likely impacts of future changes in productivity will be. Our results indicate that per-recruit reference harvest rates are more sensitive to perturbations when the equilibrium catch or population size per recruit, as functions of the harvest rate, have less curvature near the reference point. Overall our results suggest that per recruit reference points will, with some exceptions, usually increase if (1) growth rates increase, (2) natural mortality rates increase, or (3) fishery selectivity increases to an older age. [ABSTRACT FROM AUTHOR]

This short communication synthesizes the available catch information for British Columbia marine fisheries from 1873 to present and presents an electronic database consistent with the Atlas of Fisheries Impacts in preparation by the Sea Around Project at the University of British Columbia. Included in the estimates are targeted landings (both reported and unreported), by catch, discards, and illegal catch for industrial, recreational and subsistence fisheries. Governmental and non-governmental data sources are utilized, as well as previous catch reconstructions and estimates of illegal, unreported and unregulated (IUU) fisheries. Catch estimates are compared to data in FAO Fishery and Aquaculture statistics. Unreported catch rates increased slowly and consistently throughout the early history of BC’s fisheries, peaking in 1963 at about 700,000 tonnes per year. The rate dropped in the 1970s and 1980s to about half that amount, then rose again to a second similar peak in the late 1990s. The rate subsequently declined to about 200,000 tonnes per year. Contemporary FAO catch statistics document about 80% of total landings. [ABSTRACT FROM AUTHOR]

Estimating technical and economic efficiency, of traditional fishery sector, are considered as study objectives. Study results support fishing policy makers to adopt policies, which optimize the fishing resource use. In addition to save natural stock of fish, and determine the number fishing efforts, which satisfy the Maximum Sustainable Yield (MSY) of fish. Primary data collected by personal interviews with traditional fishermen at Republic Of Yemen, Hodeida Province, at fishing seasons in 2012 and 2013, are the main source of study data, in addition to the secondary data .The Data Envelopment Analysis (DEA) approach used for estimating technical and economic efficiency, based on fishing methods ( Hocks and Gill Nets), engine horsepower, and fishing boat sizes. Small boats, using Hocks fishing method and 60 horsepower engines, were technically less efficient than that for small boats using 40 horsepower engine. The first one can increase its yield by 14%, while the second one by only 9% using the same fishing resources. Large boats using 60 horsepower engine, and Gill Net fishing method, were more technically efficient than that for large boats using 40 horsepower engine. Small boats, using Hock fishing method, would increase its economic efficiency from 73% to 95% by increasing its engine horsepower from 60 to 70. While, large boats using Hocks get the highest economic efficiency, 84%, using 60 horsepower engine. Large boats using Gill Net fishing method can reduce costs by 7% of fishing costs and achieve the same level of production. [ABSTRACT FROM AUTHOR]

Catch rates and sizes of hingebeak shrimp Rhynchocinetes uritai Kubo, 1942 were studied with two types of traps: bait traps that were exposed for 1-2 days and unbaited "refuge traps" exposed for 2-4 weeks. Shrimp were collected twice a month from June 2010 to May 2012 on rocky substrata in Oura Bay, Shimoda, Japan. Overall the numbers of shrimp caught did not differ between the two trap types, but when adjusted for soak times, the bait traps had substantially higher catch rates than the refuge traps. Addition of light to the bait traps had no significant effect on catch rates. However, shrimp in the baited traps were significantly larger than those in the refuge traps. The results show that size distribution can be greatly affected by trap type. Consequently, using two types of traps simultaneously increases not only the catch efficiency but also ensures that all sizes of the reproductively mature shrimp population are sampled in adequate numbers, which is especially important in protandric hermaphrodites. [ABSTRACT FROM AUTHOR]

Seasonal changes in composition and yield of artisanal fishery catches may occur due to natural fluctuations in hydrological regime, fishers, and gear used. In this context, the present study aimed to test the hypothesis that the hydrological cycle of the Araguaia River influences the activity of small-scale commercial fishing by examining the following predictions: fishery yield is influenced by the hydrological regime; the main species exploited through artisanal fishing can change with variations in hydrological regime; and there are differences between male and female fishers in both yield and main exploited species due to differences in the sites that they explore and the gear that they use. Results from the study demonstrated a significantly higher fishery yield during the low-water season, when the catch per unit effort (CPUE) was 24.8 kg/fisher/day, compared to an ebb season CPUE of 19.9 kg/fisher/day. The main species caught by artisanal fisheries was indeed influenced by the hydrological regime of the Araguaia River and the fisher's gender, which was associated with differences in fishing locations and gear used. These findings suggest that both Araguaia River hydrology and fisher gender should be taken into consideration in developing management strategies for achieving sustainable yields. Of note, our results for fishery yields were 305 % higher than official Brazilian estimates for the entire Araguaia basin over the same period, which suggests underestimation in the official statistics. [ABSTRACT FROM AUTHOR]

The North Carolina charter boat fishery was surveyed in 1978 and provided a comprehensive assessment of the species catch composition and economic impacts. This fishery was surveyed again in 2007–2008 to provide a more recent representation of the effects and impacts on tourism and coastal fish populations. We analyzed and compared the species catch composition, type of fishing trips (inshore vs. offshore), and anglers' residency (in state vs. out of state) between these two surveys. Overall, in 2007–2008 the northern district was mainly characterized by offshore fishing trips by out‐of‐state anglers during summer and fall months, whereas the central and southern districts were primarily characterized by in‐state anglers making inshore (southern district) and offshore (central district) trips occurring mainly during summer (southern district) and fall (central district). Since 1978, the fishery in the northern and central districts has expanded further offshore, mainly targeting larger pelagic species. The fishing effort in the southern district, although expanding further offshore, has concentrated on reef species and on coastal pelagic as secondary target species. Larger, technologically more advanced boats may explain the observed patterns. This result may also be attributed to the adoption of species‐specific fishing regulations after 1978. En 1978 realizaron un estudio de la pesquería de botes de alquiler en Carolina del Norte, en el que se brinda una evaluación sistemática de la composición por especies de la captura y sus impactos económicos. Esta pesquería fue estudiada nuevamente en 2007–2008 con el fin de tener una representación más reciente de los efectos e impactos en el turismo y las poblaciones ícticas costeras. Entre ambos estudios, se analizó y comparó la composición por especies de la captura, tipo de viajes de pesca (costeros vs. fuera de la costa) y la residencia de los pescadores (del estado vs. fuera del estado). En 2007–2008 el distrito norte se caracterizó por presentar, durante el verano y otoño, viajes de pesca hacia fuera de la costa realizados por pescadores de fuera del estado; mientras que los distritos centro y sur se caracterizaron por los viajes costeros (distrito sur) y fuera de la costa (distrito central) efectuados por pescadores del estado durante el verano (distrito sur) y el otoño (distrito central). Desde 1978, la pesquería en los distritos norte y central se ha expandido hacia fuera de la costa, dirigiendo el esfuerzo principalmente a especies pelágicas más grandes. El esfuerzo de pesca en el distrito sur, aunque también se ha expandido hacia fuera de la costa, se ha concentrado en especies arrecifales y, como especies objetivo secundarias, en pelágicos costeros. Los patrones observados pueden explicarse por el uso de barcos más grandes y tecnológicamente más avanzados. Este resultado también puede atribuírsele a las regulaciones pesqueras especie‐específicas adoptadas después de 1978.provocó condiciones favorables localizadas para que se incrementara el esfuerzo de embarcaciones alquiladas. [ABSTRACT FROM AUTHOR]

Trap nets are commonly used to collect WalleyeSander vitreusbroodstock for spawning as part of culture and stocking programs. We compared overnight catch rates of Walleyes captured in two trap net sizes (small [0.9- × 1.5-m frame, 0.9-m-diameter hoop, single throat, 0.9- × 15.2-m lead, 19-mm knotted mesh] and large [1.5- × 1.8-m frame, 1.5-m-diameter hoop, double throated, 1.5- × 30.5-m lead, 19-mm knotless mesh]) to determine the relative efficiency of each size for broodstock collection. Sampling was completed during the spring of 2013 and 2014 soon after ice-out at three waters in South Dakota. In all but two cases, total Walleye CPUE in large trap nets was significantly higher than that in small trap nets. However, length-frequency distributions between the two net sizes generally were similar. The use of large trap nets will result in higher numbers of broodstock collected than with the smaller nets, likely offsetting the additional labor required to deploy and retrieve the larger traps. Received August 18, 2014; accepted October 27, 2014 [ABSTRACT FROM AUTHOR]

At the world scale, many exploited species are currently threatened or undermined by human activities, particularly fishing. Given this situation, establishing artificial habitats (AHs) and marine protected areas (MPAs) is seen as a way of both conserving biodiversity and managing fishing activities. AHs have two main effects: (1) they attract fish from the surrounding areas and concentrate them in the AH, and (2) they increase the capacity of the environment, as a result of the installation of new individuals or, in some cases, of new species. MPAs decrease fish accessibility by constraining the spatial distribution of the fishing effort. We have developed a system of ordinary differential equations (ODEs) that can be used to describe the evolution of fish density, fishing effort, and landings depending on whether AHs are deployed in a MPA or in a fishing area. The analytical study of the ODE system is simplified by means of assuming that processes occur on different time scales. Fish reproduction and landings were assumed to occur at a “slow” time scale, whereas, fish displacement was assumed to occur at a “fast” time scale. For both scenarios of AHs implementation (in an MPA or in a fishing area), we show the existence of different equilibria according to hypotheses based on a purely attractive or purely productive effect of the AH. In all cases, the deployment of AHs in the fishing area leads to an equilibrium with lower fish biomass and lower fish landings than when AHs are deployed within the MPA. This suggests that AHs should not be fished in order to maximize long term fish productivity and fish landings in the surrounding areas. In addition, we attempt to establish a correspondence between our theoretical results and the management plan for artisanal fisheries on the Senegalese coast, which includes the implementation of both AHs and MPAs. This suggests that there is not enough coordination between the non-governmental organizations deploying the AHs and the institutions managing MPAs. Indeed, AHs are usually either immersed in an MPA or subject to local fishing ban, but in fact regulation is inadequate. In this context, the deployment of AHs as part of fisheries management would be premature and could have potentially adverse effects on the resource. [ABSTRACT FROM AUTHOR]

Some fish stock assessments are conducted in regions that contain no-take marine reserves (NTMRs). NTMRs are expected to lead to spatial heterogeneity in fish biomass by allowing a buildup of biomass inside their borders while fishing pressure occurs outside. Stock assessments do not typically account for spatial heterogeneity caused by NTMRs, which may lead to biased estimates of biomass. Simulation modeling is used to analyze the ability of several stock assessment configurations to estimate current biomass after the implementation of a single, large NTMR. Age-structured spatial operating models with three patterns of ontogenetic movement are used to represent the 'true' population dynamics. Results show that assessing populations as a single stock with use of fishery catch-rate data and without accounting for the NTMR results in severe underestimation of biomass for two of the movement patterns. Omitting fishery catch-rate data or allowing time-varying dome-shaped selectivity after NTMR implementation leads to improved estimates of current biomass, but severe bias in estimated trends in biomass over time. Performing separate assessments for fished areas and NTMRs leads to improved estimation performance in the absence of movement among assessment areas, but can severely overestimate biomass otherwise. Performing a spatial assessment with estimation of movement parameters among areas was found to be the best way to assess a species, even when movement patterns were unknown. However, future work should explore the performance of spatial assessments when catchability varies among areas. [ABSTRACT FROM AUTHOR]

This paper discusses spatial patterns in small-scale fishing in Africa. It is located in Lake Victoria where since the 1990s a vibrant Nile perch fishing for overseas export developed. Focusing on a very small area in the Ugandan part of the lake, the paper uncovers a larger diversity in fishermen's responses to the dynamic environment of the Nile perch sector than a widely adopted generic model predicts. To understand this better, the paper looks at the social practices of Nile perch fishermen, uncovering the operation of different, spatially situated, fishing styles. These styles structure the social relations that the fishermen mobilise, the symbolic meanings they attach to their gear, and the values that inspire their decision-making. By thus looking at socio-cultural factors the paper hopes to contribute to an emerging spatial perspective on small-scale fishing in Africa that begins with an interest in actual social practice. [ABSTRACT FROM AUTHOR]

The common dentex Dentex dentex (Linnaeus, 1758) is an iconic marine coastal fish in the Mediterranean Sea. It is a demersal sparid fish (0-200 m), that grows to a maximum length of 100 cm and a weight of 13 kg, with a relatively long life span (more than 20 years). As a high trophic level predator, it holds a key position in coastal marine food webs. The common dentex is of great economic importance for both artisanal (small-scale coastal fisheries) and recreational fishing. Despite its economic and ecological importance, scientific data on this species in its natural environment are still very scant. The global commercial catch of common dentex has fluctuated over the last 60 years on an interannual time scale, and has declined significantly since the 1990s. There are few data regarding fishing effort and total catch from recreational fishing for common dentex, but it appears that this species is particularly targeted by this activity. The common dentex is now classified as 'vulnerable' in the Red List of Threatened Species in the Mediterranean Sea. This review summarizes the current literature on D. dentex in regard to biology, ecology, parasitology, population structure, commercial and recreational fishing, and management regulations. Future research directions to fill gaps in current knowledge are suggested. [ABSTRACT FROM AUTHOR]

This Comment was prompted by the substantial difference in weir catch estimates in the Gulf between (i) those reported by Al-Abdulrazzak and Pauly (2014. Managing fisheries from space: Google Earth improves estimates of distant fish catches. ICES Journal of Marine Science, 71(3), 450–454), who used Google Earth to count weir numbers, and (ii) those available from official national statistics provided by two major weir fishing countries (Bahrain and Iran). Satellite imageries, including Google Earth, are powerful tools for collecting data on visible structures when verified with adequate ground validation. However, an extension of their contribution to improving overall catch estimates is rather limited without having solid information on daily catch, which will substantially differ according to time and area, and fishing season lengths. It was noted that Al-Abdulrazzak and Pauly (2013) introduced positive biases through their interpretation of Google Earth images and data treatment. They included several assumptions, such as removing the impact of poor visibility, correcting grids of low resolutions, estimating number of unseen weirs, and applying daily catch rates higher than referenced observed values. The overall extent of such potential positive bias could be more than six times that which we considered reasonable. This Comment also corrects misconceptions about “FAO catch data”, discusses other available national data, and introduces the existence of the Regional Commission for Fisheries (RECOFI), a mechanism for fisheries management in the Gulf region, and its recent activities to collect more complete catch and effort data separated by gear. [ABSTRACT FROM PUBLISHER]

Recreational fishing effort greatly fluctuates in space and time. Therefore, one of the most relevant conceptual issues when managing recreational fishing is to understand the primary complexities associated with anglers' preferences in selecting site and day, and the way that these choices affect the catch. However, two practical pitfalls (data acquisition and statistical issues) are hampering progress towards the understanding of this problem. In this study, we propose several strategic improvements and apply them to the recreational squid fishery in Palma Bay (Balearic Islands). The spatial scenario (20 km width) was surveyed 63 times (visual censuses) during two years. For each of the 173 grid cells (1 km2) into which Palma Bay was divided, the fishing effort (number of recreational boats targeting squid) was recorded. In addition, a number of variables intended to summarize any potential driver of anglers' choices were also recorded. The principal drivers of squid recreational fishing in Palma Bay appeared to be expected harvest and distance to the nearest port, but the effect of these variables was clearly modulated by sea conditions. The fine-scale estimates of effort (daily predictions for each 1 km2 cell) provided here represent the first step towards understanding angler preferences, estimating total catches, and selecting the best management options for avoiding conflicts between stakeholders, thus ensuring resource sustainability. [ABSTRACT FROM PUBLISHER]

Fisheries management agencies and fishing industry representatives depend on reliable estimates of fish biomass and mortality for the determination of sustainable catch levels. Lack of data or misreporting may be reasons for unreliable stock assessment, which, in turn, may result in advice that does not reflect the availability of fisheries resources. It has been suggested that the mixed pelagic trawl fisheries in the Baltic represent a case of biased estimates of fish biomass and mortality resulting from misreporting. Here, we estimate the degree of misreporting in the Swedish pelagic fishery (1996–2009) and propose an approach for reconstructing historical catches based on commercial effort data. The analysis suggests that total catches have been underestimated during part of our study period and that systematic misreporting of species composition has taken place over the whole study period. The analysis also suggests that there is overcapacity in the fishery and that such economic incentive could explain the general patterns of misreporting. Applying our method for fisheries with suspected misreporting could significantly improve assessment accuracy, reduce uncertainty and thereby allow for a better link between catches and resource levels. [ABSTRACT FROM PUBLISHER]

Fish aggregating devices (FADs) are deployed to aggregate fish over a limited area to improve fish catch. Fish enhancing devices (FEDs), which are FADs deployed in no-fishing areas, are fast gaining popularity as a fisheries management tool in the western Pacific. Yet, the impacts of utilizing FADs and FEDs are not yet well understood. In this work, we used a mean-field model to assess the effects of utilizing FADs and FEDs on stock biomass and catch. Our results indicate that using FADs enhances catch per boat when total fishing pressure is low, but can exacerbate fishery collapse when fishing effort is high. On the other hand, a FED-based system can increase the resistance of the fishery to collapse. A FED-based fishery may thus serve as pelagic marine protected areas and/or refugia. In a quota-based system, where fishing time is tied to catch quota, a phase transition occurs: both catch and biomass abruptly shift to low levels without warning. Deploying FADs to act as FEDs in a high quota fishery can prevent this phase transition resulting to a stabilizing effect. [ABSTRACT FROM PUBLISHER]

Changes in mean trophic level ( MTL) of catches have been widely used to reflect the impact of industrial fisheries on aquatic ecosystems because this measure represents the relative abundance of fished species across the trophic level spectrum. In this study, fisheries data from six important freshwater lakes at the middle-lower Yangtze River and Huaihe River reach of Southern China from 1949 to 2009 were used to evaluate changes in catch MTL. After fishery markets opened at 1985, fish catches increased significantly in all the lakes. Lakes Poyang and Dongting, which were dominated by omnivores and connected to the Yangtze River, showed no significant change in catch MTL before and after 1985. Catch MTL in lakes Taihu and Hongze increased significantly due to an increase in the proportion of pelagic zooplanktivorous. Catches in Lake Chaohu were dominated by zooplankton-feeding lake anchovy, Coilia ectenes Temminck & Schlegel and icefish, Neosalanx taihuensis Chen, while Lake Donghu was dominated by phytoplanktivorous carps. Due to low biodiversity, catch MTL of these two lakes showed no significant change before and after 1985. Both fisheries-based and human activities-based drivers influenced the structure and catch MTL of fisheries in Chinese freshwater lakes. [ABSTRACT FROM AUTHOR]

This paper describes the catch per unit effort (CPUE) standardization using three models for data mining (support vector regression, neural network and tree regression model) and two conventional statistical methods (analysis of variance and generalized linear model) using the actual fishery data for southern bluefin tuna Thunnus maccoyii. Statistical performances of these five models were compared based on mean square error, mean absolute error and three correlation coefficients, which are measured by the difference between the observed and the corresponding predicted values. As a result, the performance of support vector regression is equivalent to (or better than) that of neural networks, and these two models are superior to the tree regression model, analysis of variance, and generalized linear model based on CPUE analyses of actual fishery data for southern bluefin tuna. We suggest a simple method for factorial analysis to extract the CPUE year trend based on the predicted values obtained from these data mining models. This method is expected to contribute markedly to reduce the difficulty of estimating the CPUE year trends by these models for data mining and should be applied to CPUE analyses because of its ease of use, general versatility and high performance . [ABSTRACT FROM AUTHOR]

Lost or abandoned fishing gear made of synthetic fibers or plastics that do not decompose in the sea. These gear result in 'ghost fishing', that retain their function as fishing gear. To solve this problem, we developed fishing gear made of aliphatic polyester (PBS/PBAT), which is biodegraded by microorganisms after a certain period. The marine fishing performance of the biodegradable material of tubular pots for conger eel was compared with that of commercial pots in the southern coastal sea of Korea, where fishing gear loss rates are high. A comparative analysis of the elastic recovery of different types of funnel material was conducted. Two types of fishing gear were tested: (1) a pot with a body and funnel made of biodegradable materials and (2) a commercial pot made of recycled polyethylene (PE). Then, field experiments were conducted on the two pot types, which were arranged alternately. The funnel rips made of biodegradable material showed better elastic recovery than that of the commercial pot. Marine fishing performance of the biodegradable pots was similar to that of the commercial pots (Mann-Whitney test, p > 0.05). There was also no significant difference in the catch per unit effort (CPUE) by the Mann-Whitney test, p > 0.05. Thus, biodegradable materials represent an environmentally friendly alternative to recycled PE for fabricating tubular pots to catch conger eel. [ABSTRACT FROM AUTHOR]

The skipjack tuna is the main tuna species caught in Brazil with pole and live-bait. Samples taken during 1984-1986 and the 2004-2009 periods provided length, weight and age data. A comparison of the population structure was made showing a decrease in the median and means of fork length in the 80's (median: 55 cm) and recent years (median: 51 cm), an increased participation of smaller individuals (40 cm) in recent catches, a high variability of lengths in each year class and a decrease of the condition factor K. These results indicate alterations in the population structure and dynamics. The von Bertalanffy growth parameters calculated for the recent years were L∞ = 669 mm; k = 0.24 yr-1; to = -3.8. CPUE data for the studied period seems to be stable (mean annual catch of 20,000 ton). However, the unit of effort used in Brazil (fishing days) does not reflect changes in fishing power and technology properly as occurred during 30 years of exploitation. It is concluded that the present situation requires a close monitoring of the fishery. [ABSTRACT FROM AUTHOR]

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Two indicators of fish exploitation, catch per unit effort ( CPUE) and yield per unit area, were used with surveys of small-scale fishery landings to compare two African reservoirs that differ in their level of fish exploitation, being high for Selingue Reservoir and low for Manantali Reservoir, both located in West Africa. The heavy exploitation in Selingue Reservoir induced a decline in catches per fishing trip (9.5 kg trip−1), whereas the catch remained high at Manantali Reservoir (17.0 kg trip−1). Moreover, the annual fish yield per unit area was lower for Manantali Reservoir (19 kg ha−1) than for Selingue Reservoir (79 kg ha−1). There was no relationship between the Morphoedaphic Index and catches for the two reservoirs. Rather, only the fishing effort and annual water-level variations defined the reservoir fish yields. Based on the results of the present study, it appears that CPUE and fish yield per unit area represent simple and robust indicators for describing the impacts of fishing intensity in aquatic ecosystems. [ABSTRACT FROM AUTHOR]