Comparative analysis of artisanal and recreational fisheries for Dentex dentex in a Marine Protected Area

The common dentex, Dentex dentex (L.), is an iconic marine coastal fish in the Mediterranean Sea. This study was performed in the Bonifacio Strait Natural Reserve (BSNR), (NW Mediterranean Sea). The aims were to: (1) evaluate temporal variation of the artisanal fishing of common dentex (2000–2012); (2) compare and quantify catch rates, fishing techniques and catch composition for artisanal and recreational fisheries, and determine the influence of management measures by both activities; and (3) estimate the production of both artisanal and recreational fisheries. Fishery data were collected from different artisanal fishing surveys (onboard fishing vessels and landings) and recreational fishing surveys (roving). The gears with the highest rates of exploitation were longline (3554 g per 100 hooks) and Trolling (351 g boat^?1 h^?1 ±SE), respectively, for artisanal and recreational fishing. This study showed that catches by both activities were quantitatively higher in partially protected areas than outside them. Production estimations suggest that the recreational fishery contributes significantly to fishing mortality and that it can magnify the negative effects of artisanal fisheries. Specific measures are needed for the sustainable fishery management of common dentex.     

Seabird interactions and by‐catch in the anchovy pelagic trawl fishery operating in northern Argentina

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Multicriteria estimate of coral reef fishery sustainability

A holistic basis for achieving ecosystem‐based management is needed to counter the continuing degradation of coral reefs. The high variation in recovery rates of fish, corresponding to fisheries yields, and the ecological complexity of coral reefs have challenged efforts to estimate fisheries sustainability. Yet, estimating stable yields can be determined when biomass, recovery, changes in per area yields and ecological change are evaluated together. Long‐term rates of change in yields and fishable biomass‐yield ratios have been the key missing variables for most coral reef assessments. Calibrating a fishery yield model using independently collected fishable biomass and recovery data produced large confidence intervals driven by high variability in biomass recovery rates that precluded accurate or universal yields for coral reefs. To test the model's predictions, I present changes in Kenyan reef fisheries for >20 years. Here, exceeding yields above 6 tonnes km^?2 year^?1 when fishable biomass was ~20 tonnes/km² (~20% of unfished biomass) resulted in a >2.4% annual decline. Therefore, rates of decline fit the mean settings well and model predictions may therefore be used as a benchmark in reefs with mean recovery rates (i.e. r = 0.20–0.25). The mean model settings indicate a maximum sustained yield (MSY) of ~6 tonnes km^?2 year^?1 when fishable biomass was ~50 tonnes/km². Variable reported recovery rates indicate that high sustainable yields will depend greatly on maintaining these rates, which can be reduced if productivity declines and management of stocks and functional diversity are ineffective. A number of ecological state‐yield trade‐off occurs as abrupt ecological changes prior to biomass levels that produce MSY.     

China's distant‐water fisheries in the 21st century

We conservatively estimate the distant‐water fleet catch of the People's Republic of China for 2000–2011, using a newly assembled database of reported occurrence of Chinese fishing vessels in various parts of the world and information on the annual catch by vessel type. Given the unreliability of official statistics, uncertainty of results was estimated through a regionally stratified Monte Carlo approach, which documents the presence and number of Chinese vessels in Exclusive Economic Zones and then multiplies these by the expected annual catch per vessel. We find that China, which over‐reports its domestic catch, substantially under‐reports the catch of its distant‐water fleets. This catch, estimated at 4.6 million t year^?1 (95% central distribution, 3.4–6.1 million t year^?1) from 2000 to 2011 (compared with an average of 368 000 t·year^?1 reported by China to FAO), corresponds to an ex‐vessel landed value of 8.93 billion € year^?1 (95% central distribution, 6.3–12.3 billion). Chinese distant‐water fleets extract the largest catch in African waters (3.1 million t year^?1, 95% central distribution, 2.0–4.4 million t), followed by Asia (1.0 million t year^?1, 0.56–1.5 million t), Oceania (198 000 t year^?1, 144 000–262 000 t), Central and South America (182 000 t year^?1, 94 000–299 000 t) and Antarctica (48 000 t year^?1, 8 000–129 000 t). The uncertainty of these estimates is relatively high, but several sources of inaccuracy could not be fully resolved given the constraints inherent in the underlying data and method, which also prevented us from distinguishing between legal and illegal catch.     

Nutrient and nitrogen isotope monitoring of an aquaculture fishery in North Queensland,Australia

A one‐time monitoring event was initiated by an aquaculture fishery in North Queensland to assess if the discharges from the aquaculture fishery were increasing nutrient input into the Great Barrier Reef Marine Park. Leaf samples from Avicennia marina (grey mangrove) were used to compare the nitrogen (N) and phosphorous (P) concentrations, and δ¹⁵N values in the receiving waters of the adjacent creeks and a set of reference sites established in a neighbouring creek. The same indicators were also measured in macroalgae from the nutrient extraction ponds. The mangrove leaves in the Mixing Zone of the receiving creek were slightly elevated in N concentrations (22 mg g^?1 compared to 17.5 mg g^?1 at the Reference sites) and δ¹⁵N values (6.5 compared to 4.5 at the Reference sites) showing there was an influence from the outputs of the aquaculture fishery. However, P concentrations were the same in the Mixing Zone and Reference sites. Downstream of the Mixing Zone, the concentration of N and P, and the δ¹⁵N values in the Receiving Waters were the same as the Reference sites, at levels considered normal in other studies. These results show that aquaculture fisheries can be managed to maintain nutrients at reference levels in mangrove foliage in estuaries of the receiving zones.     

Evaluation and impact assessment of culture‐based fisheries to enhance fish yield in small reservoirs in Odisha State,India

The present study investigates the success of stocking fingerlings of Indian major carps ‐Gibelion catla (Hamilton), Labeo rohita Hamilton and Cirrhinus mrigala Hamilton – to enhance fish yield in 58 small reservoirs in Odisha State, India. Fish stocking and yield data were collected from State Fisheries Department, Odisha. The relationships between area, stocking density and fish yield of different size groups of reservoirs were assessed using the Pearson correlation coefficient (r). Fish yield increased significantly (p < 0.05, t‐test) from 204 kg/ha/year in 2012–13 to 323 kg/ha/year in 2013–14 due to adoption of CBF. The corresponding per capita fish production increased from 398 kg fisher^?1 year^?1 to 702 kg fisher^?1 year^?1 benefitting more than 8,000 fisher households. Reservoirs in the size group 100–500 ha showed the highest response of fish yield with respect to stocking of fingerlings. The size of fingerlings at stocking and area of the reservoir had greater impact on enhancing fish yield. Stocking had a profound positive impact on fish yield. This study forms a baseline evaluation of the impact of stocking on small tropical reservoirs in India. It also recommends management measures and discusses issues, and the way forward for sustainable fisheries enhancement in small tropical reservoirs in eastern India.     

Dynamics of floodplain fisheries in Bangladesh, results of 8 years fisheries monitoring in the Compartmentalization Pilot Project

Floodplain fisheries were monitored from 1992 until 2000 in the Compartmentalization Pilot Project in Tangail, Bangladesh. In permanent floodplains about 165 ± 28 kg ha^?1 of fish was caught annually. For seasonal floodplains, this figure was 83 ± 23 kg ha^?1 yr^?1. The fish catch exhibited a strong seasonal variation, with the highest catch in October, when the floodwater recedes towards the river, and the lowest catch during the dry season in April/May. The annual catch varied with the extent of flooding, with high catches in wet years and low catches in dry years. The extent of flooding was quantified through a Flood Index. Plotting the annual yields against this Flood Index provided a significant relation (P < 0.05), confirming the existence of a flood pulse. The fishing effort (f) and the catch‐per‐unit‐effort (CPUE) were significantly related (P < 0.05), whereby the fishing effort increased with increasing CPUE. The results are discussed within the frame of fisheries management in Bangladesh and highlight the need for long‐term data for proper evaluation of fisheries projects and the development of management schemes, and the difficulty of applying standard surplus production models in floodplain fisheries.     

The use of anglers' catches to monitor fish populations in large water bodies, with particular reference to the River Derwent, Derbyshire, England

Abstract. Nearly 2000 marked coarse fish of four species were introduced into a stretch in the middle reaches of the River Derwent. Derbyshire, England in an attempt to estimate the fish population size from catch returns. It was estimated that 800 dace, 1975 roach, 1481 chub and 366 bream were present in the reach and the density of the fish population (0·35 fish m^?2) was low. The validity of employing anglers as samplers in a mark-recapture exercise to estimate fish population size in large fisheries is discussed. Angler catch data were collected from angling clubs holding competitions on the Hoveringham Fishery on the lower reaches of the River Derwent over the period 1973/1974 to 1983/1984 to assess the impact of achange in management strategy on the fishery in 1979. Catch rates improved gradually until 1979/1980 when a dramatic increase occurred. This elevated catch rate, in excess of 400 g man-h^?1, was maintained and, in recent years, further enhanced (>500 g man-h^?1). The improvement was the result of a strong year-class of chub entering the catchable cohort and dominating anglers' catches and not the change in management policy.     

Evaluation of observer‐ and industry‐based catch data in a recreational charter fishery

There is international recognition for greater inclusion of recreational fisheries catch data in species, fisheries and ecosystem assessments. Recreational charter fisheries provide important social services and contribute to total species catches. This study compares and validates industry logbook catch and effort data (1,357 trips) against observer data (154 trips) across six ports in a recreational charter fishery in eastern Australia. The mean numbers of clients and fishing effort (hours) per trip varied inconsistently between data sources and among ports. Logbooks did not adequately report released catches, and the mean number of species retained per trip was consistently underestimated in logbooks compared to observer data. For both data sources, catch rates of total individuals and key species displayed similar trends across different units of effort; catch per hour, client, client/hour and trip. The mean catch rates of total individuals and most key species, except those retained for bait, were similar across data sources, as were estimates of total fleet harvests. The length compositions of retained catches of some key species displayed truncation of larger organisms in the observer data whereas other species did not. Despite the shortcomings of the logbook data, future fishery and species monitoring strategies could include industry and observer data sources.     

Wasted fishery resources: discarded by-catch in the USA

Fishery by‐catch, especially discarded by‐catch, is a serious problem in the world's oceans. Not only are the stocks of discarded species affected, but entire trophic webs and habitats may be disrupted at the ecosystem level. This paper reviews discarding in the marine fisheries of the USA; however, the type, diversity and regulatory mechanisms of the fisheries are similar to developed fisheries and management programmes throughout the world. We have compiled current estimates of discarded by‐catch for each major marine fishery in the USA using estimates from existing literature, both published and unpublished. We did not re‐estimate discards or discard rates from raw data, nor did we include data on protected species (turtles, mammals and birds) and so this study covers discarded by‐catch of finfish and fishable invertebrates. For some fisheries, additional calculations were required to transform number data into weight data, and typically length and weight composition data were used. Specific data for each fishery are referenced in Harrington et al. (Wasted Resources: Bycatch and discards in US Fisheries, Oceana, Washington, DC, 2005). Overall, our compiled estimates are that 1.06 million tonnes of fish were discarded and 3.7 million tonnes of fish were landed in USA marine fisheries in 2002. This amounts to a nationwide discard to landings ratio of 0.28, amongst the highest in the world. Regionally, the southeast had the largest discard to landings ratio (0.59), followed closely by the highly migratory species fisheries (0.52) and the northeast fisheries (0.49). The Alaskan and west coast fisheries had the lowest ratios (0.12 and 0.15 respectively). Shrimp fisheries in the southeast were the major contributors to the high discard rate in that region, with discard ratios of 4.56 (Gulf of Mexico) and 2.95 (South Atlantic). By‐catch and discarding is a major component of the impact of fisheries on marine ecosystems. There have been substantial efforts to reduce by‐catch in some fisheries, but broadly based programmes covering all fisheries are needed within the USA and around the world. In response to international agreements to improve fishery management, by‐catch and discard reduction must become a regular part of fishery management planning.     

The effect of a closed area and beach seine exclusion on coral reef fish catches

Fish landing data from the Mombasa Marine National Park (MNP) and a marine reserve exploited by various gears were studied over a 5‐yr period to determine the influence of the closed area and different gears in fisheries. The number fishing and boats per landing site was constant, but total and catch per unit effort progressively declined in all sites on an annual basis irrespective of the existence of a marine reserve, exclusion of the beach seines or use of gear. Differences between landing sites were most pronounced when analysed on a catch per area as opposed to the more standard catch per fisherman, suggesting compensation in human effort when catches decline. A marine reserve next to a closed area that excluded beach seines had the highest catch per area (5.5 kg ha^?1 month^?1) despite having the highest density of fishermen (0.07 ± 0.02 fishermen ha^?1 month^?1). The annual rate of decline in the catch was lower than the other sites at around 250 g day^?1 compared with 310–400 g day^?1 in the other sites. One landing site, which excluded beach seine landings for more than 20 yrs, had a high catch per area (～5.3 kg ha^?1 month^?1), but after experiencing a doubling in the effort of other gears (line, speargun and trap), the catch per fisherman and area were reduced. Environmental or habitat degradation and excessive effort remain the most likely explanation for the overall declines in catch from 1995 to 1999. Closed areas and beach seine exclusion have the potential to increase catch rates, but the first often reduces the total fishing area and possibly leads to a loss of total catch, at least on a time scale of less than 10 yrs. The exclusion of beach seines can lead to an increase in other gear types that can also cause reductions in catch.     

Fisheries,large‐scale trade,and conservation of seahorses in Malaysia and Thailand

• 1. All seahorse species (genus Hippocampus) are listed under CITES Appendix II, requiring that exports of these fishes must be regulated for sustainability. Preliminary trade surveys and anecdotal reports suggested Malaysia and Thailand represented an important source for seahorses used globally in traditional medicine, curios, and aquarium display, but few historic trade or fisheries data are available. Baseline information about pre‐CITES catch and trade is essential for managing seahorse fisheries and trade under CITES, and for understanding present‐day effects of CITES regulation on the seahorse trade.
• 2. In 1998–1999, seahorse fisheries and trade in both countries were assessed by interviewing participants at many levels of the trade and corroborating those surveys with official trade documents.
• 3. Seahorses were found to be landed primarily as trawl bycatch. Malaysia's catch of 2900 kg year^?1 was less than the estimated domestic consumption (5500–6000 kg year^?1), whereas Thailand's catch of 6600 kg year^?1 apparently far exceeded domestic consumption (～520 kg year^?1).
• 4. Both countries imported seahorses from and exported to other Asian nations. Import statistics from Hong Kong SAR and Taiwan recorded maximum annual trade from Malaysia at 1280 kg year^?1. Trade surveys indicated that Thailand exported at least 5000 kg annually (similar to the estimation of catch), but national Customs records reported 10 500 kg year^?1 in exports, supported by official import records from Hong Kong SAR and Taiwan which indicated that Thailand was the source of up to 11 400 kg year^?1.
• 5. Fishers and traders in both countries reported decreasing availability of seahorses, raising conservation concerns. These apparent declines, in combination with substantial domestic consumption, point towards the challenges that Malaysia and Thailand face in establishing sustainable levels of exports under CITES. Copyright © 2010 John Wiley & Sons, Ltd.

     

Effectiveness of eugenol sedation to reduce the metabolic rates of cool and warm water fish at high loading densities

Effects of eugenol (AQUI‐S^®20E, 10% active eugenol) sedation on cool water, yellow perch Perca flavescens (Mitchill), and warm water, Nile tilapia Oreochromis niloticus L. fish metabolic rates were assessed. Both species were exposed to 0, 10, 20 and 30 mg L^?1 eugenol using static respirometry. In 17°C water and loading densities of 60, 120 and 240 g L^?1, yellow perch controls (0 mg L^?1 eugenol) had metabolic rates of 329.6–400.0 mg O₂ kg^?1 h^?1, while yellow perch exposed to 20 and 30 mg L^?1 eugenol had significantly reduced metabolic rates of 258.4–325.6 and 189.1–271.0 mg O₂ kg^?1 h^?1 respectively. Nile tilapia exposed to 30 mg L^?1 eugenol had a significantly reduced metabolic rate (424.5 ± 42.3 mg O₂ kg^?1 h^?1) relative to the 0 mg L^?1 eugenol control (546.6 ± 53.5 mg O₂ kg^?1 h^?1) at a loading density of 120 g L^?1 in 22°C water. No significant differences in metabolic rates for Nile tilapia were found at 240 or 360 g L^?1 loading densities when exposed to eugenol. Results suggest that eugenol sedation may benefit yellow perch welfare at high densities (e.g. live transport) due to a reduction in metabolic rates, while further research is needed to assess the benefits of eugenol sedation on Nile tilapia at high loading densities.     

Feeding the pearl oyster Pinctada margaritifera during reproductive conditioning

This study aimed to model the food intake of P. margaritifera to examine the relationship between food level and reproductive activity. The effect of microalgae concentration on ingestion rate and assimilation efficiency was studied over a broad concentration range, using a mixture of Isochrysis galbana and Chaetoceros gracilis. Reproductive effort was assessed using three microalgae concentrations of 0.5, 7 and 18 cell μL^?1. Reproductive status was assessed by gonad development index (GDI) – the ratio of the gonad surface to the visceral mass surface – and histological analysis of the gonad based on the presence (continuous or discontinuous) or the absence of gonial cells (GC). Ingestion is a saturating function of seston concentration for bivalves modelled with an adapted Michaelis‐Menten function. The maximum ingestion rate of P. margaritifera adults was 193.50 × 10⁶ cell h^?1 g^?1 dw and the half saturation coefficient was 15 cell μL^?1. The concentration of 18 cell μL^?1, supplied for 45 days, induced a significantly higher GDI than the other treatments. GC decreased significantly and even stopped when pearl oysters were under‐fed, suggesting that the mitotic process of the germinal stem cells was altered. Differentiation of germinal stem cells therefore appears to be controlled by food availability.     

Optimization of blue mussel (Mytilus edulis) seed culture using recirculation aquaculture systems

By introducing recirculation aquaculture systems (RAS) in the nursery phase of the blue mussel (Mytilus edulis) (17–18 mm), we aimed at a similar growth and survival and a similar water quality compared to the commonly used flow‐through systems (FTS). To calculate water flow and size of the biofilter, a series of experiments were done to determine clearance rate (9.26 mL min^?1), pseudo faeces threshold (60 000 cells Pavlova lutheri mL^?1), nitrogen production (0.00065 mg TAN h^?1 ind^?1 and 1.6 × 10^?5 mg NO₂–N h^?1 ind^?1) and oxygen consumption (0.03 ± 0.01 mg O₂ h^?1 ind^?1). RAS showed no significant differences in water quality (0.06 mg TAN L^?1; 7.7 mg O₂ L^?1) and growth performance of mussel seed specific growth rate (SGR = 5% day^?1) after the experimental period of 4 weeks compared with FTS. The low water refreshment, 10% per day, as well as the constant chlorophyll concentrations (9.76 ± 1.06 μg L^?1), suggests the potential of RAS as culture system for mussel seed.     

The sea cucumber fishery in Australia's Great Barrier Reef Marine Park follows global patterns of serial exploitation

Tropical sea cucumber fisheries follow a predictable pattern of serial depletion. Overfishing is exacerbated in developing countries where management systems lack capacity to control large numbers of fishers influenced by poverty. In contrast, the tropical sea cucumber fishery in Australia's World Heritage listed Great Barrier Reef Marine Park (GBRMP) is operating in a developed high‐income country with relatively few licensed fishers to manage. The development of this fishery is reviewed here in a meta‐analysis of catches from 1991 to 2011. The fishery expanded to replace high‐value teatfish species (Holothuria whitmaei and H. fuscogilva), fished heavily in initial stages of the fishery, with newly commercialized medium‐value species such as burying blackfish (Actinopyga spinea) and curryfish (Stichopus herrmanni). These two species now constitute 80% of total catch. The annual average catch of burying blackfish was 208 tonnes years 2004–11 and curryfish catches increased rapidly at an average annual pace of 200% from 2007–11. This serial harvest pattern occurred in the absence of baseline studies and without independent resource assessments, information required to inform relevant harvest predictions and to determine fishery impacts. This situation does not support ecologically relevant and adaptive decision‐making in management and the unfolding catch patterns in the GBRMP follow those in low‐income developing countries. The missing knowledge and lack of data serve as arguments to support precautionary reductions in harvests and extending fallow periods in fishing zones.     

Changes in a coral reef fishery along a gradient of fishing pressure in an Indonesian marine protected area

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Considering recreational catch and harvest in fisheries management at the bio‐regional scale

Abstract The Gulf of Carpentaria in northern Australia supports several commercial fisheries and a largely tourist‐based recreational fishery. The results of a survey of 427 recreational fishing parties visiting the main town, Karumba, between March and September 2006 were examined using the bootstrap method to estimate confidence intervals for mean tourist catch and harvest of grunter, Pomadasys kaakan (Cuvier), and other recreational target species. Tourist anglers harvested between 99.8 and 117 t of P. kaakan and 32.6–38.2 t of blue salmon, Eleutheronema tetradactylum (Shaw), during the survey period. Resident recreational anglers harvested an additional 15–35 t of P. kaakan, but very little E. tetradactylum. In comparison, commercial harvest was 19 t of P. kaakan and 64 t of E. tetradactylum in the whole of the Queensland section of the Gulf of Carpentaria. The results underscore the need for appropriately collected recreational fishing data to support integrated fisheries management at the bioregional scale, and in the case of angling‐based tourist destinations, underpin a diversification of the tourist product.     

Population dynamics and stock status of cobia,Rachycentron canadum,caught in Australian recreational and commercial coastal fisheries

Abstract Age and growth of Rachycentron canadum (L.) was studied in northern and eastern Australia to provide data for a preliminary assessment of the stock and to explore possible fisheries management strategies using minimum legal lengths. Fish collected from commercial and recreational fisheries ranged in size and weight from 125 to 1633 mm fork length (FL) and 0.031 to 55 kg respectively. Annual growth increments in sectioned otoliths formed by November–December. Estimated ages ranged from 0 to 7 yr for both genders. Longevity was estimated to be at least 13 yr. Von Bertalanffy growth function parameters were L = 1160 mm FL, K = 0.63 yr^?1 and t₀ = ?0.21 yr^?1. Rachycentron canadum reach 600 mm FL in their first year and over 1000 mm FL in 3 years. Natural and total mortalities were estimated at 0.35 yr^?1 and 0.85 yr^?1, respectively. Populations of R. canadum may be vulnerable to growth overfishing under the current minimum legal length of 750 mm total length (TL) in Queensland waters. An increase in minimum legal length to 850 mm TL is recommended.     

Performance of rainbow trout, Salmo gairdneri Richardson, in a put-and-take fishery, and influence of anglers' behaviour on catchability

Abstract. Stock, catch and fishing effort statistics for a 12·5-ha lowland pul-and-lake trout fishery have been used to compute the ‘catchability’ of rainbow trout, Salmo gairdneri Richardson, during the fishing seasons 1980–1983. Seasonal trends in the fishes’ susceptibility to capture by fly-fishing are apparent but there was no indication that, in this fishery, newly stocked fish were more vulnerable than the longer-term residents. This consistency of recapture rates of rainbow trout, relative to the population available, is a function both of the fish's behaviour and that of the anglers themselves, and it is suggested that for management purposes the latter must be taken into account. In the fishery studied rainbow trout grew well at fish densities below 60 kg ha^?1, but even with overall recapture levels exceeding 80% the yield of the fishery was less than the weight of fish stocked. The selection of strains of rainbow trout which satisfy the requirements of sport fisheries is discussed.