Growth overfishing in the brown shrimp fishery of Texas, Louisiana, and adjoining Gulf of Mexico EEZ

Growth overfishing in the brown shrimp, Farfantepenaeus aztecus, fishery in inshore (estuarine) and offshore (Gulf of Mexico) territorial waters of Texas and Louisiana, and adjoining waters of the United States’ (U.S.) Exclusive Economic Zone (EEZ), and its potentially detrimental economic consequences to the harvesting sector, have not been among major concerns of Federal and State shrimp management agencies. Three possible reasons include (1) environmentally influenced variations in recruitment that cause wide fluctuations in annual landings, which tend to obscure effects of fishing, (2) competition between inshore and offshore components of the harvesting sector, and (3) partitioning of management jurisdiction among a Federal council and two State agencies. Wide variations in landings led to beliefs that high levels of fishing mortality were tolerable and recruitment overfishing was of no major concern. This encouraged somewhat laissez-faire management approaches that allowed fishing effort to increase over the years.Our objectives were to determine whether growth overfishing occurred in this fishery during 1960–2006, and whether and how decreases in size of shrimp within the landings, in response to increases in fishing effort, affected inflation-adjusted annual (calendar year) ex-vessel value of the landings, i.e., their value to the harvesting sector. Growth overfishing occurred in the early 1990s, and then abated as fishing effort declined due to rising fuel costs and competition from imported shrimp. However, inflation-adjusted annual ex-vessel value of the landings peaked in 1985, prior to growth overfishing.Management actions implemented in 2001 for Texas’ territorial waters, and in the EEZ off Texas and Louisiana in 2006, should limit future fleet expansion and increases in fishing effort, thereby reducing the chances of growth overfishing and its potentially detrimental economic impacts on the harvesting sector. Growth overfishing should be included among the guidelines for future management of this brown shrimp fishery.     

Using fishers' anecdotes, naturalists' observations and grey literature to reassess marine species at risk: the case of the Gulf grouper in the Gulf of California, Mexico

Designing fishing policies without knowledge of past levels of target species abundance is a dangerous omission for fisheries management. However, as fisheries monitoring started long after exploitation of many species began, this is a difficult issue to address. Here we show how the ‘shifting baseline’ syndrome can affect the stock assessment of a vulnerable species by masking real population trends and thereby put marine animals at serious risk. Current fishery data suggest that landings of the large Gulf grouper (Mycteroperca jordani, Serranidae) are increasing in the Gulf of California. However, reviews of historical evidence, naturalists’ observations and a systematic documentation of fishers’ perceptions of trends in the abundance of this species indicate that it has dramatically declined. The heyday for the Gulf grouper fishery occurred prior to the 1970s, after which abundance dropped rapidly, probably falling to a few percent of former numbers. This decline happened long before fishery statistics were formally developed. We use the case of the Gulf grouper to illustrate how other vulnerable tropical and semi‐tropical fish and shellfish species around the world may be facing the same fate as the Gulf grouper. In accordance with other recent studies, we recommend using historical tools as part of a broad data‐gathering approach to assess the conservation status of marine species that are vulnerable to over‐exploitation.     

Managing fisheries is managing people: what has been learned?

Understanding the behaviour of fishermen is a key ingredient to successful fisheries management. The aggregate behaviour of fishing fleets can be predicted and managed with appropriate incentives. To determine appropriate incentives, we should look to successes to learn what works and what does not. In different fisheries incentive systems have been found to reduce the race‐for‐fish and make fisheries profitable, to stimulate stock rebuilding, to reduce bycatch, and to provide for reductions in illegal fishing. Yet, success can be evaluated in many dimensions, but is, in fact, rarely done – per cent overfished seems to be the dominant measure of performance. I evaluate the yield lost due to overfishing in several ecosystems and contrast the situation of North Atlantic cod where considerable yield is lost, to fisheries in New Zealand and the west coast of the USA where lost yield due to overfishing is very small. Much more systematic evaluation of the other aspects of fisheries performance is greatly needed. From examples explored in this paper I conclude that prevention of overfishing can be achieved with strong central governments enforcing conservative catch regulations, but economic success appears to require an appropriate incentive structure.     

Effects of cryptic mortality and the hidden costs of using length limits in fishery management

Fishery collapses cause substantial economic and ecological harm, but common management actions often fail to prevent overfishing. Minimum length limits are perhaps the most common fishing regulation used in both commercial and recreational fisheries, but their conservation benefits can be influenced by discard mortality of fish caught and released below the legal length. We constructed a computer model to evaluate how discard mortality could influence the conservation utility of minimum length regulations. We evaluated policy performance across two disparate fish life‐history types: short‐lived high‐productivity (SLHP) and long‐lived low‐productivity (LLLP) species. For the life‐history types, fishing mortality rates and minimum length limits that we examined, length limits alone generally failed to achieve sustainability when discard mortality rate exceeded about 0.2 for SLHP species and 0.05 for LLLP species. At these levels of discard mortality, reductions in overall fishing mortality (e.g. lower fishing effort) were required to prevent recruitment overfishing if fishing mortality was high. Similarly, relatively low discard mortality rates (>0.05) rendered maximum yield unobtainable and caused a substantial shift in the shape of the yield response surfaces. An analysis of fishery efficiency showed that length limits caused the simulated fisheries to be much less efficient, potentially exposing the target species and ecosystem to increased negative effects of the fishing process. Our findings suggest that for overexploited fisheries with moderate‐to‐high discard mortality rates, reductions in fishing mortality will be required to meet management goals. Resource managers should carefully consider impacts of cryptic mortality sources (e.g. discard mortality) on fishery sustainability, especially in recreational fisheries where release rates are high and effort is increasing in many areas of the world.     

Effects of fishing practice changes on pelagic shark longline captures in the Gulf of Gabes,Tunisia

1. In order to increase their catches, longliners targeting sharks in the Gulf of Gabes, Tunisia, have increased the number of hooks per basket and have included new bait types instead of mackerel (Scomber scombrus). This paper reports the effects of these changes on catch composition, catch rates, size distribution, life‐stage captures, and mortality at haulback.
2. Data from 48 and 96 longline sets, carried out during the shark fishing seasons of 2007 and 2008, with two hooks per basket, and 2016 and 2017, with five hooks per basket, respectively, were examined to assess the effect of gear change. Moreover, the effects of bait types were inspected based on 33 fishing sets using whole mackerel, 19 using salema (Sarpa salpa) halves, and 27 using pieces of stingray (Dasyatis spp.), sampled during 2016 and 2017.
3. The species composition indicated that longliners expand the vertical distribution of their hooks to operate from the surface to the bottom. The catches with both longline designs were dominated by sandbar shark (Carcharhinus plumbeus). Despite gear changes, the catch rate of C. plumbeus decreased by 42.21%, suggesting population decline. The size composition indicated a shift towards larger specimens, mainly adult females, which could jeopardize the shark population. Moreover, the mortality of the main species at haulback seems to be affected by the design of the longline.
4. The bait used, mainly pieces of stingray, significantly increased the catch rate of sandbar shark, which suggests a greater attractiveness of the new bait; however, fish size and mortality rates at haulback were unchanged in response to bait variation.
5. The fishery operates in shark nursery grounds, which exposes these fish (principally C. plumbeus) to considerable exploitation pressure. The new fishing practices intensified the pressure and thus the risk of a rapid depletion of populations. To preserve the shark species in the area, the use of new gear and attractive bait should be banned.

     

Biochemical Aspects of Schistosome Behaviour

The haematophagous blood tiematodes that comprise the genus Schistosoma live in a stable environment with an adequate food supply and an efficient waste disposal system.

The main food is glucose obtained from the host blood and assimilated through the tegument Other dietary factors are assimilated through the tegument or the gut epithelium. The male fluke supplements and augments the diet of the female who is thus able to concentrate on egg production.

Live flukes resist attack by the host by secreting an immunologically inert envelope and by incorporating unchanged host serum protein into their structures. They can also incorporate host structural fatty acids unchanged.     

A century of fishery data documenting the collapse of smooth‐hounds (Mustelus spp.) in the Mediterranean Sea

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Reconstructing the history of human impacts on coastal biodiversity in Chile: constraints and opportunities

• 1. Although Chile is at the forefront in evaluating experimentally the importance of human harvesting impacts on coastal biodiversity, there are no evaluations of such impacts on a long‐term historical basis (tens to thousands of years). Different types of archival information (i.e. contemporaneous, archaeological, and palaeontological) were used to carry out a research programme based on the historical assessment of the impacts and intensity of resource extraction on coastal biodiversity along the Chilean coast.
• 2. In addition to recent scientific literature, different sources of contemporaneous information (e.g. museum collections, old reports and accounts) can reveal the human impacts observed in the more recent past. Furthermore, the large number of prehistoric shell middens along the entire Chilean coast offer access to ～11 000 years of history along the entire coast, although the faunal composition, structure, and dynamics of most of them remain largely unstudied.
• 3. Finally, the rich and widespread fossil record of some marine groups provides the opportunity to reconstruct the structure and dynamics of benthic communities during different phases of human influence (e.g. pre‐human, prehistoric harvesting, and modern harvesting).
• 4. Preliminary comparisons of fossil versus modern bivalve assemblages suggest marked changes in the species composition. Human impacts seem very recent and shifts in the structure of benthic assemblages may have occurred only a few centuries/decades ago.
• 5. In contrast, prehistoric harvesting, although intense, was apparently not enough to cause a profound impact on coastal ecosystems. The approach herein envisaged can provide the basis to build a historical baseline to evaluate the human impacts on the coastal biodiversity in the region. Copyright © 2009 John Wiley & Sons, Ltd.

     

Status of giant clam resources around Okinawa‐jima Island,Ryukyu Archipelago,Japan

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Human‐induced gradients of reef fish declines in the Hawaiian Archipelago viewed through the lens of traditional management boundaries

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