Selectivity matters: Rules of thumb for management of plate‐sized,sex‐changing fish in the live reef food fish trade

Effective management of fisheries depends on the selectivity of different fishing methods, control of fishing effort and the life history and mating system of the target species. For sex‐changing species, it is unclear how the truncation of age‐structure or selection of specific size or age classes (by fishing for specific markets) affects population dynamics. We specifically address the consequences of plate‐sized selectivity, whereby submature, “plate‐sized” fish are preferred in the live reef food fish trade. We use an age‐structured model to investigate the decline and recovery of populations fished with three different selectivity scenarios (asymptotic, dome‐shaped and plate‐sized) applied to two sexual systems (female‐first hermaphroditism and gonochorism). We parameterized our model with life‐history data from Brown‐marbled grouper (Epinephelus fuscoguttatus) and Napoleon fish (Cheilinus undulatus). “Plate‐sized” selectivity had the greatest negative effect on population trajectories, assuming accumulated fishing effort across ages was equal, while the relative effect of fishing on biomass was greatest with low natural mortality. Fishing such sex‐changing species before maturation decreased egg production (and the spawning potential ratio) in two ways: average individual size decreased and, assuming plasticity, females became males at a smaller size. Somatic growth rate affected biomass if selectivity was based on size at age because in slow growers, a smaller proportion of total biomass was vulnerable to fishing. We recommend fisheries avoid taking individuals near their maturation age, regardless of mating system, unless catch is tightly controlled. We also discuss the implications of fishing post‐settlement individuals on population dynamics and offer practical management recommendations.     

Biological and socioeconomic implications of recreational boat fishing for the management of fishery resources in the marine reserve of Cap de Creus (NW Mediterranean)

A survey of coastal recreational boat fishing was conducted in summer 2006 in the marine reserve of Cap de Creus (NW Mediterranean) to assess the biological and socioeconomic implications of this leisure activity. Recreational boat fishers employ four different fishing techniques: bottom fishing rod, fluixa, trolling and surface fishing rod. Although the targeted species depend on the fishing method used, a total of 33 fish species were identified in the catch (8 were pelagic or benthopelagic and the rest were demersal). Fishing effort was high since fishers fished an average of 4 h/day, 8 days/month and nearly 6 months/year. Apart from the highly varied exploitation of the fauna, recreational fishing in Cap de Creus has a large economic effect on the local economy since the majority of fishers were visitors who were spending holidays in one of the villages belonging to the Park, where most of expenditures related to angling activities were made. Overall, results highlight the pressure that recreational boat fishing exerts on fish communities, particularly on littoral, demersal ones. Considering these biological and socioeconomic implications, the competition between recreational and artisanal fishers for littoral resources and the low level of compliance with the current sport fishing regulations, the implementation of a comprehensive management strategy in Mediterranean costal areas is needed.     

Changes in population parameters and behaviour of blue cod (Parapercis colias; Pinguipedidae) in Long Island—Kokomohua Marine Reserve,Marlborough Sounds,New Zealand

• 1 With the establishment of the 619‐ha Long Island—Kokomohua Marine Reserve in April 1993, a biological monitoring programme designed to investigate changes due to the total no‐take legislation applied to the reserve was initiated.
• 2 Size, distribution and behaviour of blue cod (Parapercis colias; Pinguipedidae) were investigated using baited hooks at reserve and control rubble bottom habitats annually from 1993 to 2000. Blue cod abundance was estimated using visual diver strip transects annually for a period of 9 years from 1992 to 2001.
• 3 A total of 5628 blue cod (2436 reserve and 3192 control specimens) were captured, measured and released. Two years after the reserve was established, the average size of blue cod was 22.4 mm larger inside the reserve compared with control sites outside it.
• 4 Over the duration of the study, the mean length of blue cod captured using baited hooks increased in the no‐take reserve, but declined at the control sites. By the end of the study, in April 2000, the proportion of large blue cod >330 mm in length in the reserve was 35% compared with <1% at the control sites, where recreational fishing activities occurred.
• 5 Blue cod catch rates from experimental fishing in the reserve increased within 11 months of removal of recreational fishing activities and continued to increase up to 47 months, in contrast to the control areas where recreational fishing was permitted, catch rates remained consistently low. Increased catch rates in the reserve were not due to increased blue cod abundance, rather an increase in the proportion of naïve fish in the population.
• 6 From March 1998 to the end of the study, the density of blue cod in the reserve was significantly higher compared with the control sites. This increase was primarily due to an increase in the density of larger blue cod >300 mm length in the reserve and a corresponding small decline in the density of these larger fish at the control sites.
• 7 It is concluded that the cessation of recreational fishing in the reserve had resulted in an increase in blue cod size, catch rate and abundance and also in a change to blue cod behaviour.

Copyright © 2001 John Wiley & Sons, Ltd.     

Indirect effects of bottom fishing on the productivity of marine fish

One quarter of marine fish production is caught with bottom trawls and dredges on continental shelves around the world. Towed bottom‐fishing gears typically kill 20–50 per cent of the benthic invertebrates in their path, depending on gear type, substrate and vulnerability of particular taxa. Particularly vulnerable are epifaunal species, which stabilize the sediment and provide habitat for benthic invertebrates. To identify the habitats, fisheries or target species most likely to be affected, we review evidence of the indirect effects of bottom fishing on fish production. Recent studies have found differences in the diets of certain species in relation to bottom fishing intensity, thereby linking demersal fish to their benthic habitats at spatial scales of ~10 km. Bottom fishing affects diet composition and prey quality rather than the amount of prey consumed; scavenging of discarded by‐catch makes only a small contribution to yearly food intake. Flatfish may benefit from light trawling levels on sandy seabeds, while higher‐intensity trawling on more vulnerable habitats has a negative effect. Models suggest that reduction in the carrying capacity of habitats by bottom fishing could lead to lower equilibrium yield and a lower level of fishing mortality to obtain maximum yield. Trawling effort is patchily distributed – small fractions of fishing grounds are heavily fished, while large fractions are lightly fished or unfished. This patchiness, coupled with the foraging behaviour of demersal fish, may mitigate the indirect effects of bottom fishing on fish productivity. Current research attempts to scale up these localized effects to the population level.     

Biological implications of recreational shore angling and harvest in a marine reserve: the case of Cape Creus

• 1. Recreational shore fishing along the coast of the marine reserve of Cap de Creus (NW Mediterranean) was studied in 2007 and 2009 based on roving creel surveys (on‐site angler surveys during which anglers' harvests are examined by the survey clerk). The study aimed to assess the biological impacts of this leisure activity on coastal fish stocks and the potential risks arising from the use of exotic baits.
• 2. Recreational shore fishers employ seven different fishing techniques, of which the bottom fishing rod (a fishing rod whose hooks, together with the bait, lie on the bottom or near it by means of a heavy weight) is by far the most widely used method (nearly 90% of observations). In total, 25 fish species were identified in the catch from the bottom fishing rod.
• 3. The estimated annual shore fishing catches (c.3 tons) are much lower than those obtained by recreational boat and spear fishing (c.20 tons each), and those from commercial (artisanal) fishing (c.50 tons). The weighted mean vulnerability index and trophic level values in the catch from the bottom fishing rod are 52.2 and 4.03, respectively.
• 4. A minimum of 43% of the baits used by the shore anglers were live, non‐native species (mostly polychaetes).
• 5. Overall, results highlight the impact of shore angling on coastal fish communities of a protected area and the increasing environmental risks arising from the use of exotic marine baits, which constitute a potential and unregulated vector of introduction of non‐native species in the Mediterranean. Copyright © 2011 John Wiley & Sons, Ltd.

     

Effects of fisheries management on fish communities in the floodplain lakes of a Brazilian Amazonian Reserve

Abstract –  We compared fish abundance, diversity and species composition between lakes open (fished) and closed (no-take) to fishing activities in Mamirauá Sustainable Development Reserve in the Central Brazilian Amazon, in order to investigate potential influences of the common-based management. We sampled 1483 fishes from 70 species through gillnet fishing during the low-water season, in seven fished and seven no-take lakes. Contrary to expected, the mean values for abundance, size, diversity and species-richness of fish did not differ between fished and no-take lakes. There was no difference between fished and no-take lakes considering only the abundance of the 14 fish species more intensely targeted by fishermen. However, the abundance of an important commercial fish, the tambaqui ( Colossoma macropomum ) was higher in no-take lakes. Such data from a rapid assessment may be useful to monitor this and other fishery co-management schemes.     

Effects of intensive fishing on the perch population in a large oligotrophic lake in eastern Finland

The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield.     

Integrating recreational fisheries data into stock assessment: implications for model performance and subsequent harvest strategies

Understanding the impacts of recreational fishing on commercially fished stocks is becoming increasingly relevant for fisheries managers. However, data from recreational fisheries are not commonly included in stock assessments of commercially fished stocks. Simulation models of two assessment methods employed in Australia's Commonwealth fisheries were used to explore how recreational fishery data can be included, and the likely consequences for management. In a data‐poor management strategy for blue eye trevalla, Hyperoglyphe antarctica (Carmichael), temporal trends in recreational catch most affected management outcomes. In a data‐rich age‐structured stock assessment for striped marlin, Kajikia audax (Philippi), estimates of stock status were biased when recreational catches were large or when the recreational fishery targeted different size classes than the commercial fishery and these data were not integrated into the assessment. Including data from recreational fishing can change perceptions of stock status and impact recommendations for harvest strategies and management action. An understanding of recreational fishery dynamics should be prioritised for some species.     

Recreational charter fishery attributes and variation in key species catches and discards: Resource management considerations

Strategic long‐term sampling programmes that deliver recreational catch, effort and species demographic data are required for the effective assessment and management of recreational fisheries and harvested organisms. This study used a spatially and temporally stratified observer programme to examine variation in the rates, quantities and lengths of retained and discarded catches of key species in a recreational charter fishery. Geographic region, but not season, significantly influenced catch rates of key demersal species, being driven by temporally persistent latitudinal clines in environmental conditions influencing species distributions. There was considerable trip‐to‐trip variation in catch rates that were attributed to localised differences in fishing operations, locations, environmental conditions and client preferences. Broad trends in retained and discarded catch rates were nevertheless, similar across different fishing effort standardisations (per‐trip, per‐hour, per‐client, per‐client/fished hour), demonstrating that the coarsest unit of effort could be used in fishery assessments. Discard rates of organisms were variable and driven by a combination of mandated legal lengths, individual client and operator preferences for particular species and sizes of organisms, and not due to attainment of catch quotas or high‐grading. This study has identified important fishery attributes that require consideration in assessing charter fisheries and stocks of recreational fish species.     

Size and age are important factors for marine sanctuaries: evidence from a decade of systematic sampling in a subtropical marine park

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Recall bias in recreational summer flounder party boat trips and angler preferences to new approaches to bag and size limits

Three innovative approaches to bag and size limits were evaluated in the recreational summer flounder Paralichthys dentatus fishery. Each approach was designed to reduce discard mortality while increasing angler satisfaction, yet still limiting recreational take within management goals. Each was compared to the 2006 legal bag and size limits on party boat trips from New Jersey and New York. Angler-specific catch data were collected during the trips, and anglers completed a questionnaire while sailing back to port. Comparison of questionnaires to observer records revealed that anglers could not accurately recall the number of fish kept or released. Anglers overestimated both kept and discarded fish by a factor of about two. Neither fishing scenario, age, sex, nor years fished significantly influenced the accuracy of survey reports of kept fish. Anglers on three of five boats over-reported landings. Reported landings were nearly accurate on two boats. Survey accuracy for reported discards was influenced by bag-and-size-limit scenario and differed among boats, sexes, and fishing experience, but no predictable pattern was evident. In particular, bias in reporting was unrelated to angler sex, age, experience, and performance on observed trips or any other criterion measured in this study. Anglers preferred the slot limit most and the 2006 legal bag and size limit least. High grading and transfer of fish among anglers were rare occurrences. Our study demonstrated that the summer flounder fishery is a consumptive fishery.     

Deep hooking,landing success and gear loss using inline and offset circle and J hooks when bait fishing for white sturgeon

The issue of deep hooking is of concern in white sturgeon, Acipenser transmontanus Richardson, fisheries because nearly all anglers use bait with a stationary presentation on the river bottom to catch them, and bait fishing is often associated with higher instances of deep hooking and hooking mortality. Deep hooking rates, landing success and catch rates were investigated for anglers bait fishing for white sturgeon using circle and J hooks with inline and offset alignments fished with both active and passive hook‐setting methods. Anglers hooked 578 white sturgeon and landed 508 fish, ranging in size from 60 to 316 cm total length (mean = 137 cm). Deep hooking rates averaged 0.6% and did not differ between hook types, hook alignments or hook‐setting methods. Landing success (the proportion of hooked sturgeon that were successfully landed) and catch rates were also equivalent between hook types, hook alignments and hook‐setting methods; landing success averaged 88% and catch rates averaged 0.27 fish/hr. Results of this study indicate that deep hooking is rare when angling for white sturgeon using standard bait‐fishing gear regardless of hook‐setting method or whether circle or J hooks were used; regulations restricting hook type in sturgeon bait fisheries are therefore unwarranted.     

Quantifying the rare: Baselines for the endangered Napoleon Wrasse,Cheilinus undulatus,and implications for conservation

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Direct evidence of limited dispersal of the reef fish Parapercis colias (Pinguipedidae) within a marine reserve and adjacent fished areas

1. Spillover of organisms from marine reserves may augment adjacent areas, and is often cited as an important reason for the establishment of marine protected areas. Spillover is dependent on residence or limited dispersal of organisms resulting in an increase in their abundance and size within a marine reserve. 2. To investigate movement (i.e. spillover versus residence) we tagged and released 90 blue cod Parapercis colias (Pinguipedidae) at each of four sites, two in and two adjacent to Long Island–Kokomohua Marine Reserve, Marlborough Sounds, New Zealand. The study was done 4–5 years after establishment of the no‐take reserve. 3. Abundances of blue cod were similar in and out of the marine reserve, but mean estimated size was 4 cm larger in the reserve than at fished sites. 4. Fewer tag resights were made in the reserve than at fished sites, and tagged blue cod were resighted at greater depths in the reserve than at fished sites. 5. Most resights (75% for fished sites, 73% for reserve sites) were made within 100 m of the tagging sites, and the number of resights declined through time, though tagged individuals were resighted up to 31 months after tagging. 6. The lower number of tag resights at reserve sites, despite the lack of extraction, is consistent with some blue cod at reserve sites moving longer distances than those at fished sites. 7. The greater size of individuals in the reserve and limited dispersal of a proportion of the population show that survivorship of blue cod is increased within marine reserves. 8. Computer simulations based on measured dispersals indicate that even marine reserves of a few hundred metres long‐shore extent have the potential to supplement fished populations nearby. 9. These data provide direct evidence of limited dispersal of the most common edible reef fish in the Marlborough Sounds. Blue cod will grow to larger sizes in marine reserves and via spillover will become available to fishers in adjacent areas of contiguous coast. Copyright © 2000 John Wiley & Sons, Ltd.     

Assessment of commercial and recreational fishing effects on trophic interactions in the Cap Roux area (north‐western Mediterranean)

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Optimising recreational harvests of blue cod: The effects of catch-and-release mortality and size selectivity

A yield-per-recruit model is developed for the recreational fishery on blue cod (Parapercis colias: Pinguipedidae) in the Marlborough Sounds, New Zealand. The model incorporates sex differences in growth rates, protogyny, minimum size limits, catch-and-release mortality and size-selective fishing. Mortality of released fish due to hooking damage and post-release predation is a potentially significant factor for blue cod management. High levels of catch-and-release mortality favour small minimum size limits and reduced fishing intensity. Even in the absence of size limits, hook and line fishing for blue cod is highly selective on larger fish and this greatly reduces the potential impact of catch-and-release mortality on yields and management choices. Catch-and-release mortality will also lower the spawning stock biomass-per-recruit and therefore has the potential to impact on stock sustainability as well as yields. In protogynous species the effects of fishing on spawning stock biomass will be different for males and females and it is important to model these separately, as well as understanding the cues for, or timing and extent of, sex change. Catch-and-release mortality can also slow the recovery of stocks when no-take rules still allow fishing for other species and therefore by-catch of the species targeted for protection. It is suggested that a small reduction in size limit and a small increase in daily bag limit relative to present regulations, would result in optimal yields from this fishery. Predation on fish released by recreational anglers is less widely reported than mortality due to hooking damage but both have the potential to negate the benefits of minimum size limits.     

Importance of recreational fisheries in the Guadiana River Basin in Portugal

The rapid expansion of recreational fishing in Portugal over the last 20 years, along with the multiplicity of pressures affecting inland fisheries, demands the urgent recognition of the social and economic values. Sport-angling information is still inadequate to formulate management actions. To address this issue, a regional survey on freshwater recreational fishing in all the municipalities of the Guadiana River Basin was carried out in 1999. The survey, based on 1998 data, provided information on the profile of anglers, preferences as regards reservoirs and sections of rivers fished, frequency of fishing trips, motivation, expenditure, fish species caught, an estimation of total catch and its destination, interest in competitions, enforcement and personal opinions. The results recommended improved communication and feedback between users, and mechanisms for future regional development and management of recreational fisheries.     

Experience counts: Integrating spearfishers’ skills and knowledge in the evaluation of biological and ecological impacts

Fishing experience and skills are not commonly considered in recreational fishery studies. To analyse potential different biological/ecological impacts of three experience levels of spearfishers (novice, intermediate and experienced), access point surveys were conducted over a period of 10 months in São Miguel Island (Azores archipelago). Groups differed in terms of catch rate and composition, species size and vulnerability (i.e. intrinsic vulnerability index of fishes to fishing). Experienced spearfishers explored different areas along the island coast, fished deeper and farther off shore, were more selective regarding fish size and target species, reached higher catch weights and had catches with a higher mean index of vulnerability. Results suggest that catch composition and rate not only depend on fish community and ecosystem health, but also on the expertise of the fishers who operate in a given area. Consequently, scientific studies should consider fishers’ experience in the survey design and data analysis to not over‐ or underestimate their potential impact.     

Fish life history,angler behaviour and optimal management of recreational fisheries

To predict recreational‐fishing impacts on freshwater fish species, it is important to understand the interplay between fish populations, anglers and management actions. We use an integrated bioeconomic model to study the importance of fish life‐history type (LHT) for determining (i) vulnerability to over‐exploitation by diverse angler types (generic, consumptive and trophy anglers), who respond dynamically to fishing‐quality changes; (ii) regulations [i.e., minimum‐size limits (MSLs) and licence densities] that maximize the social welfare of angler populations; and (iii) biological and social conditions resulting under such socially optimal regulations. We examine five prototypical freshwater species: European perch (Perca fluviatilis), brown trout (Salmo trutta), pikeperch (Sander lucioperca), pike (Esox lucius) and bull trout (Salvelinus confluentus). We find that LHT is important for determining the vulnerability of fish populations to overfishing, with pike, pikeperch, and bull trout being more vulnerable than perch and brown trout. Angler type influences the magnitude of fishing impacts, because of differences in fishing practices and angler‐type‐specific effects of LHT on angling effort. Our results indicate that angler types are systematically attracted to particular LHTs. Socially optimal minimum‐size limits generally increase with LHT vulnerability, whereas optimal licence densities are similar across LHTs. Yet, both regulations vary among angler types. Despite this variation, we find that biological sustainability occurs under socially optimal regulations, with one exception. Our results highlight the importance of jointly considering fish diversity, angler diversity and regulations when predicting sustainable management strategies for recreational fisheries. Failure to do so could result in socially suboptimal management and/or fishery collapse.     

Identifying recreational fisheries in the Mediterranean Sea through social media

The impact of recreational fishing on fish stocks remains largely unknown, as this is inherently difficult to monitor, especially in areas such as the Mediterranean Sea where many species are targeted using a variety of fishing gears and techniques. This study attempts to complement existing data sets and construct the profile of recreational fisheries in the EU‐Mediterranean countries using videos publicly available on social media. A total of 1526 video records were selected, featuring the capture of 7799 fish specimens. The results show recreational fishing is multispecies in nature (26 species contributed to >80% % of the most numerically important species caught) and exhibits a spatially homogeneous pattern, with differences in species composition being mostly dependent on the fishing technique used rather than on the country. Such findings fill an important knowledge gap on recreational fishing activities, and the methodology provides an innovative approach to gather statistics on data‐poor thematic areas that can potentially complement other data sets, such as the EU Data Collection Multi‐Annual Programme.