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.     

Footprints of fixed-gear fisheries in relation to rising whale entanglements on the U.S. West Coast

On the U.S. West Coast, reports of whales entangled in fishing gear increased dramatically in 2014. In this study, a time series of fishing activity maps was developed from 2009 to 2016 for the four fixed-gear fisheries most commonly implicated in entanglements. Maps were generated using vessel monitoring system (VMS) data linked to port-level landings databases, which were related to entangled whale reports over the same time period and with modelled distributions of humpback whales Megaptera novaeangliae Borowski. Over the full study period, neither marked increases in fishing activity nor changes in fisheries footprints within regions with high whale densities were detected. By contrast, a delayed fishery opening in California due to a harmful algal bloom in spring of 2016 led to ~5–7 times average levels of Dungeness crab Metacarcinus magister (Dana) fishing activity, which was consistent with a high rate of entanglement in that year. These results are consistent with current hypotheses that habitat compression caused by a marine heatwave increased the overlap of whales with fishing activity, despite minimal changes in the fisheries themselves. This study adds to literature on bycatch of protected species in otherwise sustainable fisheries, highlighting the value of using VMS data for reducing human–wildlife conflict in the ocean.     

Reducing seabird bycatch in longline, trawl and gillnet fisheries

With an increasing number of seabird species, particularly albatross and petrels, becoming threatened, a reduction of fishery impacts on these species is essential for their future survival. Here, mitigation methods to reduce and avoid seabird bycatch are assessed in terms of their ability to reduce bycatch rates and their economic viability for longline, trawl and gillnet fisheries worldwide. Factors influencing the appropriateness and effectiveness of a mitigation device include the fishery, vessel, location, seabird assemblage present and season of year. As yet, there is no single magic solution to reduce or eliminate seabird bycatch across all fisheries: a combination of measures is required, and even within a fishery there is likely to be refinement of techniques by individual vessels in order to maximize their effectiveness at reducing seabird bycatch. In longline demersal and pelagic fisheries, a minimum requirement of line weighting that achieves hook sink rates minimizing seabird bycatch rates should be tailored with a combination of strategic offal and discard management, bird‐scaring lines (BSLs) and night‐setting, particulary in Southern Hemisphere fisheries. Urgent investigation is needed into more effective measures at reducing seabird interactions with trawl nets and gill nets. In trawl fisheries, a combination of offal and discard management, the banning of net monitoring cables, paired BSLs, and a reduction in the time the net is on or near the surface are likely to be the most effective in reducing seabird interactions with the warp cables and net. Few seabird bycatch reduction methods have been developed for gillnet fisheries, although increasing the visibility of the net has been shown to reduce seabird bycatch. Further studies are required to determine the efficacy of this technique and its influence on target species catch rates.     

Contemporary and emerging fisheries in The Bahamas—Conservation and management challenges,achievements and future directions

The harvest of marine resources has long‐standing cultural and economic importance to The Bahamas and other small island developing states. Tourists and residents place a demand on local marine resources, particularly Caribbean spiny lobster, Panulirus argus (Latreille), queen conch, Lobatus gigas (Linnaeus) and Nassau grouper, Epinephelus striatus (Bloch), and many fishery products are also sold on the global market. Illegal, unreported and unregulated fishing coupled with inadequate regulations and enforcement are the main factors contributing to the decline of Bahamian fisheries along with other anthropogenic impacts. This article reviews the status of fisheries management in The Bahamas using economically and ecologically important species as case studies to highlight conservation successes, knowledge gaps and deficiencies in existing management approaches. The review concludes with an examination of how emerging fisheries and improved conservation management strategies have the potential to improve economic and food security throughout the archipelago.     

Reconciling traditional inland fisheries management and sustainability in industrialized countries, with emphasis on Europe

In northern industrialized countries, the inland fisheries sector has long been dominated by recreational fisheries, which normally exploit fish for leisure or subsistence and provide many (poorly investigated) benefits to society. Various factors constrain the development and existence of inland fisheries, such as local user conflicts, low social priority and inadequate research and funding. In many cases, however, degradation of the environment and loss of aquatic habitat are the predominant concerns for the sustainability of inland fisheries. The need for concerted effort to prevent and reduce environmental degradation, as well as conservation of freshwater fish and fisheries as renewable common pool resources or entities in their own right is the greatest challenge facing sustainable development of inland waters. In inland fisheries management, the declining quality of the aquatic environment coupled with long‐term inadequate and often inappropriate fisheries management has led to an emphasis on enhancement practices, such as stocking, to mitigate anthropogenic stress. However, this is not always the most appropriate management approach. Therefore, there is an urgent need to alter many traditional inland fisheries management practices and systems to focus on sustainable development. This paper reviews the literature regarding the inputs needed for sustainability of inland fisheries in industrialized countries. To understand better the problems facing sustainable inland fisheries management, the inland fisheries environment, its benefits, negative impacts and constraints, as well as historical management, paradigms, trends and current practices are described. Major philosophical shifts, challenges and promising integrated management approaches are envisaged in a holistic framework. The following are considered key elements for sustainable development of inland fisheries: communication, information dissemination, education, institutional restructuring, marketing outreach, management plans, decision analysis, socioeconomic evaluation and research into the human dimension, in addition to traditional biological and ecological sciences. If these inputs are integrated with traditional fisheries management practices, the prospects for sustainability in the inland fisheries will be enhanced.     

Length and sex-specific associations between spiny dogfish (Squalus acanthias) and hydrographic variables in the Bay of Fundy and Scotian Shelf

The associations between spiny dogfish ( Squalus acanthias ) and hydrographic variables (temperature, salinity and depth) were examined in the Bay of Fundy and Scotian Shelf from 1970 to 1998. Data were obtained from standard groundfish bottom trawl surveys. Dogfish sex affected habitat associations. Males were found to occupy bottom water of significantly higher salinities and depths than that occupied by females. Length also significantly affected habitat associations. Smaller dogfish occupied relatively deep, high salinity bottom water compared with larger dogfish. Overall, the occupied temperatures, salinities and depths were significantly different from those which were available. Dogfish occupied warmer temperatures along a narrow range (6.62–9.19°C) compared with those which were available (1.57–9.35°C). Occupied salinity (32.70–34.43 ppt) and occupied depth (88.62–184.66 m) were also distributed along a narrower range than available salinity (32.16–34.79 ppt) and available depth (55.00–218.10 m). Sex-specific, length-specific and overall environmental preference by dogfish may bias traditional `offshore' groundfish surveys while large scale changes in hydrographic parameters may alter dogfish distribution and their interactions with other marine fauna.     

Remote sensing and geographical information systems: Their past, present and future use in global marine fisheries

Historically, the fishing community (e.g., fishermen, resource managers) has used remotely sensed products either in the form of direct Automatic Picture Transmission (APT) reception on a ship or FAX charts transmitted from land-based stations. Both these products have severe limitations within the context of near real-time support/management of an operational fishery. Moreover, relatively little use of geographical information systems (GIS) technologies has been made by either the fishing industry, fishery resource managers, or by the general oceanographic community. This latter omission is unfortunate because GIS has the potential to overcome two long-standing problems associated with satellite-directed fisheries: 1) the absence of information due to clouds; and 2) the general lack of support for nonpelagic fisheries. This report gives the background, motivation, and essential design elements for use of a combined remote sensing/geographical information system (RS/GIS) in an operational fishery and illustrates how a combined RS/GIS approach can be used to mitigate some of the traditional limitations in satellite-directed fisheries. Finally, an attempt is made to provide some possible directions this new technology may take during the 1990s.     

Gleaner,fisher, trader,processor: understanding gendered employment in fisheries and aquaculture

Most research on gender difference or inequities in capture fisheries and aquaculture in Africa and the Asia‐Pacific focuses on the gender division of labour. Emerging research on globalization, market changes, poverty and trends in gendered employment within this sector reveals the need to move beyond this narrow perspective. If gleaning and post‐harvesting activities were enumerated, the fisheries and aquaculture sector might well turn out to be female sphere. A livelihoods approach better enables an understanding of how employment in this sector is embedded in other social, cultural, economic, political and ecological structures and processes that shape gender inequities and how these might be reduced. We focus on four thematic areas – markets and migration, capabilities and well‐being, networks and identities, governance and rights – as analytical entry points. These also provide a framework to identify research gaps and generate a comparative understanding of the impact of development processes and socioecological changes, including issues of climate change, adaptation and resilience, on gendered employment. Without an adequate analysis of gender, fisheries management and development policies may have negative effects on people’s livelihoods, well‐being and the environment they depend on, or fail altogether to achieve intended outcomes.     

Geostatistics in fisheries survey design and stock assessment: models, variances and applications

Over the past 10 years, fisheries scientists gradually adopted geostatistical tools when analysing fish stock survey data for estimating population abundance. First, the relation between model‐based variance estimates and covariance structure enabled estimation of survey precision for non‐random survey designs. The possibility of using spatial covariance for optimising sampling strategy has been a second motive for using geostatistics. Kriging also offers the advantage of weighting data values, which is useful when sample points are clustered. This paper discusses, with fisheries applications, the different geostatistical models that characterise spatial variation, and their variance formulae for many different survey designs. Some anticipated developments of geostatistics related to multivariate structures, temporal variability and adaptive sampling are discussed.     

Post-settlement growth and mortality of brackishwater clam Corbicula japonica in the Kiso estuaries, central Japan

Different cohorts of Corbicula japonica benthic individuals (from new settlers just after larval settlement up to recruits with 12-mm shell length and more) in the Kiso estuaries, Japan were separated based on temporal changes in shell length histograms. The post-settlement growth and mortality were examined for cohorts that were successful in fishery recruitment. Three growth models (Logistic, Gompertz and ALOG) were fitted to the growth data on average shell lengths of different cohorts, the best-fitting growth model varied depending on cohort and further on cohorts that were grouped according to estuary and to either overwintering or non-overwintering. Mortality rates were estimated based on regression models fitted separately to the data on temporal changes in the log-transformed density against sampling dates of individuals before and after fishery recruitment (i.e. attaining 12-mm shell length). For most cohorts, however, there was no significant difference in mortality rates between individuals before and after fishery recruitment, although significant differences were detected in initial densities between individuals of these two groups. It may be suggested that daily mortality rate after fishery recruitment was compensated with fishery mortality, so that total mortality rate was not different between individuals of these two groups.     

Price transmission among different Atlantic salmon products in the U.S. import market

The cross-commodity price transmission is an approach to derive meaningful results from the price information, and is mostly influenced by the substitutability and complementary relations among products. Using time series data collected from the National Marine Fisheries Statistics, the present study specified and estimated cross-commodity price transmission models for 13 salmon products imported in the U.S. market. The salmon products are differentiated by form, cut, source/origin, and production environment. The estimated cross-product price transmission elasticity and degree of substitutability among them varied considerably. Whole fresh farmed Canadian and Norwegian Atlantic salmon did not have any close import substitutes in the U.S. market among the salmon products considered in the study. A reduced pricing strategy would result in an increase in U.S. salmon import market share of Chilean and U.K. Atlantic fillet fresh, if the U.S. import demand for it is relatively own-price elastic.     

Scavenger communities and fisheries waste: North Sea discards support 3 million seabirds, 2 million fewer than in 1990

Every year fisheries discard >10 million tonnes of fish. This provides a bounty for scavengers, yet the ecological impact of discarding is understudied. Seabirds are the best‐studied discard scavengers and fisheries have shaped their movement ecology, demography and community structure. However, we know little about the number of scavenging seabirds that discards support, how this varies over time or might change as stocks and policy change. Here, we use a Bayesian bioenergetics model to estimate the number of scavenging birds potentially supported by discards in the North Sea (one of the highest discard‐producing regions) in 1990, around the peak of production, and again after discard declines in 2010. We estimate that North Sea discards declined by 48% from 509,840 tonnes in 1990 to 267,549 tonnes in 2010. This waste had the potential to support 5.66 (95% credible intervals: 3.33–9.74) million seabirds in the 1990s, declining by 39% to 3.45 (1.98–5.78) million birds by 2010. Our study reveals the potential for fishery discards to support very large scavenging seabird communities but also shows how this has declined over recent decades. Discard bans, like the European Union's Landing Obligation, may reduce inflated scavenger communities, but come against a backdrop of gradual declines potentially buffering deleterious impacts. More work is required to reduce uncertainty and to generate global estimates, but our study highlights the magnitude of scavenger communities potentially supported by discards and thus the importance of understanding the wider ecological consequences of dumping fisheries waste.     

Depredation of commercial and recreational fisheries in a Danish fjord by cormorants, Phalacrocorax carbo sinensis, Shaw

Abstract The conflict between the cormorant, Phalacrocorax carbo sinensis Shaw, and commercial and recreational fisheries was investigated in the foraging area of a cormorant colony of 5000 breeding pairs in Horsens Fjord, Denmark. Depredation of commercial pound nets was studied by stocking a large net pen with hatchery-reared rainbow trout, Oncorhynchus mykiss (Walbaum). When avian predation was precluded with a cover net, background mortality was around 15% day^-1. When the cover net was removed, mortality increased to 98% day^-1. Direct observation revealed that a flock of cormorants emptied the pound net in about 30 min, consuming 110 fish weighing a total of approximately 50 kg. The cormorants were able to catch trout weighing more than 1 kg, i.e. almost 50% of their own body weight. The impact of the cormorant colony on recreational fishing in the area was studied by stocking Carlin-tagged sea trout, Salmo trutta L., smolts into the two rivers that drain into the fjord. The cormorant colony lies between the river outlets and the open sea. Tag recovery from a 3-year programme was only about 2%, compared with about 10% for smolts stocked in areas of low cormorant density.     

A comparative review of fisheries management experiences in the European Union and in other countries worldwide: Iceland,Australia, and New Zealand

This study compares the details and performance of fisheries management between the EU and a selection of other countries worldwide: Iceland, New Zealand, and Australia, which are considered in many respects to be among the most advanced in the world in fisheries management. Fisheries management in the EU, Iceland, Australia, and New Zealand has developed following different paths, despite being based on similar instruments and principles. Iceland, Australia, and New Zealand have been at the forefront of developing management practices such as stakeholder involvement, legally binding management targets (Australia, New Zealand), individual transferable quotas, and discard bans (Iceland, New Zealand). The EU has since the beginning of the 21st century taken significant steps to better involve stakeholders and establish quantitative targets through management plans, and a landing obligation is gradually being implemented from 2015 onward. The management of domestic fisheries resources in Australia, New Zealand, and Iceland has, overall, performed better than in the EU, in terms of conservation and economic efficiency. It should, however, be stressed that, compared to Australia, New Zealand, and Iceland, (i) initial over‐capacity was more of an issue in the EU when management measures became legally binding and also that (ii) EU has been progressive in developing common enforcement standards, on stocks shared by sovereign nations. The situation of EU fisheries has substantially improved over the period 2004–2013 in the northeast Atlantic, with fishery status getting close to that in the other jurisdictions, but the lack of recovery for Mediterranean fish stocks remains a concern.     

Assessing the impact of hydropower and fisheries on downstream migrating silver eel, Anguilla anguilla, by telemetry in the River Meuse

Abstract –  European eel Anguilla anguilla is in strong decline. We assessed the relative impact of fisheries and hydropower during the downstream migration of silver eel in the River Meuse in the Netherlands using radio-telemetry. For this, 16 fixed detection stations (Nedap Trail-System^®) were used, each covering the entire river width, including all outlets to sea, and two covering the entrances of the two hydropower stations present. In September 2002, 150 silver eels were surgically implanted with Nedap-transponders and released at the catch site. Of these, 121 started to migrate downstream of which 37% successfully reached the North Sea. Hydropower mortality was at least 9% and assessed to be 16–26%. Fisheries mortality was at least 16% (reported recaptures) and estimated to be 22–26%. A clear difference was found in passage behaviour at hydropower stations, where 40% showed recurrence, in contrast to the river stations where this hardly occurred, indicating a hesitation to pass the turbines. Also a difference was found in diurnal pattern; 63% of the eels that passed through the turbines did so during the first 5 h of the night, whereas for the stations on free-flowing sections this was only 35%.     

Effects of flood and drought events on multi‐species,multi‐method estuarine and coastal fisheries in eastern Australia

Abstract Multivariate patterns in commercial fisheries landings, effort and revenue from three adjacent estuarine and coastal systems were examined in eastern Australia between 9‐month periods of flood (September 2000–May 2001) and drought (September 2002–May 2003). Patterns in species landings, methods of fishing effort and revenue per species were significantly different between flood and drought. Spearman’s rank correlations between Bray–Curtis similarity matrices for landings, effort and revenue indicated that patterns in fisheries metrics represented a mixed signal of ecological response and fishers’ harvesting behaviour. Flood and drought events were associated with shifts in the species composition of landings that were reciprocated between estuarine and coastal systems. Estuarine migrant species (e.g. school prawn Metapenaeus macleayi Haswell) primarily contributed to landings during flood, whilst marine estuarine‐opportunist species (e.g. yellowfin bream Acanthopagrus australis Owen) primarily contributed to landings during drought. Flood and drought events redistributed fisheries resources between estuarine and coastal systems, modifying the bioeconomic productivity of commercial fisheries. Results indicated that flood and drought events influence commercial fisheries by modifying landings composition, fishers’ harvesting behaviour and revenue generation.     

Genetic population structure of black‐browed and Campbell albatrosses,and implications for assigning provenance of birds killed in fisheries

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