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Near extinction of a highly fecund fish: The one that nearly got away

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Abstract

Abstract It is widely assumed that commercial fisheries of highly fecund species are particularly resilient to exploitation, and that, should populations become seriously diminished, economic constraints will force fishing to cease before biological extinction can occur. Indeed, among commercially exploited marine fishes there is not one confirmed global extinction. Here we document, using nonconventional means, a story that not only questions such assumptions but that should also alert us to how little we know about significant fisheries in some parts of the world. Our case study is that of the highly threatened Chinese bahaba, Bahaba taipingensis, a member of the Sciaenidae (the drums or croakers), and an example of a fecund and commercially important group of fishes that appears to be especially vulnerable to fishing. We also demonstrate that the careful use of informal, or traditional, information can provide a powerful, sometimes unique, means of identifying and assessing the status and history of species that might be quietly slipping away before we learn anything about them.

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... Overfishing and ocean pollution in the past decade have led to a dramatic decrease in fish in the wild fisheries of China (Liu & Sadovy 2008;Sadovy & Cheung 2003). The endemic species of giant yellow croaker (Bahaba taopongensos), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung 2003). ...
... Overfishing and ocean pollution in the past decade have led to a dramatic decrease in fish in the wild fisheries of China (Liu & Sadovy 2008;Sadovy & Cheung 2003). The endemic species of giant yellow croaker (Bahaba taopongensos), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung 2003). The spotted drum (Protonobea doacanthus) and large yellow croaker (Laromochthys crocea, which is endemic to East Asia and was once one of the three top commercial marine fishes in China), have been severely depleted throughout their geographic range since the 1980s and have now almost entirely disappeared from landings (Liu & Sadovy 2008;Sadovy & Cheung 2003). ...
... The endemic species of giant yellow croaker (Bahaba taopongensos), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung 2003). The spotted drum (Protonobea doacanthus) and large yellow croaker (Laromochthys crocea, which is endemic to East Asia and was once one of the three top commercial marine fishes in China), have been severely depleted throughout their geographic range since the 1980s and have now almost entirely disappeared from landings (Liu & Sadovy 2008;Sadovy & Cheung 2003). The most recent study of Indo-Pacific humpback dolphins (Sousa chonensos, locally called the Chinese white dolphin) biosonar activity in the Pearl River Estuary indicated that its diel, seasonal and tidal patterns might be ascribed to the spatial-temporal variability of its prey (Wang et al. 2015b); however, little attention has been paid to local fishes, with only sporadic fishery distribution data with poor temporal and spatial resolution obtained from 1986-1987 by bottom trawl and in 1998 by beam trawl and hang trawl (Li et al. 2000b;Wang & Lin 2006).The fine-scale distribution pattern of humpback dolphin prey has yet to be investigated. ...
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Full-text available
Background. Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species. Methods. Underwater biological sounds in the Pearl River Estuary, China, were collected using passive acoustic monitoring, with special attention paid to fish sounds. A total of 1408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine. Results. We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2600 Hz and a majority of the energy below 4000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times that were exclusive from each other, suggesting that they might be produced by different species. According to the literature, the two section signal types of 1+1 and 1+N 10 might belong to big-snout croaker ( Johnius macrorhynus ), and 1+N 19 might be produced by Belanger's croaker ( J. belangerii ). Discussion. Categorization of the baseline ambient biological sound is an important first step in mapping the spatial and temporal patterns of soniferous fishes. The next step is the identification of the species producing each sound. The distribution pattern of soniferous fishes will be helpful for the protection and management of local fishery resources and in marine environmental impact assessment. Since the local vulnerable Indo-Pacific humpback dolphin ( Sousa chinensis ) mainly preys on soniferous fishes, the fine-scale distribution pattern of soniferous fishes can aid in the conservation of this species. Additionally, prey and predator relationships can be observed when a database of species-identified sounds is completed.
... Fishes of the family Sciaenidae, commonly known as croakers, are important components of commercial, recreational and indigenous fisheries in tropical and temperate regions worldwide (Lenanton & Potter 1987). They are targeted for their flesh and, increasingly, for their swim bladders, which are sold fresh or dried in Southeast Asia (Sadovy & Cheung 2003;Ghosh et al., 2009;Tuuli 2010). Many species of Sciaenidae have declined in recent decades due to over-exploitation and several are now considered threatened. ...
... in the 1980's led to local extirpation (James, 1994) and a fishery that once thrived in Hong Kong no longer exists (Sadovy & Cheung, 2003). ...
... The finding that P. diacanthus across northwestern Australia consists of a set of spatially structured populations with low connectivity sets a framework to develop approaches for the assessment and spatial management of the species. The collapse of the North Queensland stock and stocks in India and China (James, 1994;Sadovy & Cheung, 2003) demonstrates that P. diacanthus is prone to local depletion and our findings suggest that this vulnerability is likely due to its low dispersal and high location-specific fidelity. Stock assessment models for this species cannot assume free and frequent movement of individuals among the genetic populations stock boundaries. ...
Article
Full-text available
As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The black-spotted croaker, Protonibea diacanthus, is the only large sciaenid in coastal waters of northern Australia where it is targeted by commercial, recreational and indigenous fishers due to its food value and predictable aggregating behaviour. Localised declines in the abundance of this species have been observed, highlighting the urgent requirement by managers for information on fine and broad-scale population connectivity. This study examined the population structure of P. diacanthus across northwestern Australia using three complementary methods: genetic variation in microsatellite markers, otolith elemental composition and parasite assemblage composition. The genetic analyses demonstrated that there were at least five genetically distinct populations across the study region, with gene flow most likely restricted by inshore biogeographic barriers such as the Dampier Peninsula. The otolith chemistry and parasite analyses also revealed strong spatial variation among locations within broad-scale regions, suggesting fine-scale location fidelity within the lifetimes of individual fish. The complementarity of the three techniques elucidated patterns of connectivity over a range of spatial and temporal scales. We conclude that fisheries stock assessments and management are required at fine scales (100's km) to account for the restricted exchange among populations (stocks) and to prevent localised extirpations of this species. Realistic management arrangements may involve the successive closure and opening of fishing areas to reduce fishing pressure. This article is protected by copyright. All rights reserved.
... Understanding the effects that diet has on farmed totoaba swim bladder characteristics and composition may provide insight into their potential marketability and inform what nutritional benefits may be derived from totoaba swim bladders. In addition to the effects of diet on buche quality, a better understanding of how diet affects swim bladder size relative to fish size (Sadovy and Cheung, 2003) may also inform efforts to estimate the pressure on portions of wild populations subject to poaching. Here we address these challenges by evaluating several components of swim bladder size and quality, as well as the growth response of T. macdonaldi juveniles, fed diets in which fishmeal was differentially replaced by soy protein concentrate. ...
... Dried swim bladders of some fish, also known as fish maw, are luxury food commodities in the Chinese seafood market (Sadovy and Cheung, 2003). Fishes belonging to the family Sciaenidae (croakers) have been Table 5 Selected fatty acid composition (mg g − 1 wet tissue) of swim bladder and whole body of Tototaba macdonaldi fed diets with three inclusion levels of soy protein concentrate (SPC) in place of fishmeal. ...
... This index, never before reported for cultivated totoaba, may be useful for developing a swim bladder-body weight relationship. Such a tool, in conjunction with data on moisture content of this organ, may help infer body size of poached fish from weights of confiscated swim bladders (Sadovy and Cheung, 2003), providing insight into population structure of fish caught illegally. With respect to the dietary effects of SPC at levels of 0, 30%, and 60% on fish performance, observations from this study were consistent with Trejo-Escamilla et al. (2017), who found that growth performance of totoaba was not altered when up to 45% SPC by weight was included in the diet. ...
Article
Full-text available
Totoaba (Totoaba macdonaldi) is a large species of croaker, endemic to the upper Gulf of California in Mexico, which has been under extreme poaching pressure due to its highly valuable swim bladder, or buche. For more than 20 years, totoaba aquaculture has been developing as one, among many, conservation strategies in the ongoing management of the species. Competing with illegally poached buche requires farming high quality product. This study provides the first report of the influence of alternative aquaculture feeds-fishmeal versus soy protein concentrate (SPC)-on key cultured totoaba traits that affect the market value of its swim bladder. Since the price of farmed buche is key to the successful displacement of illegally poached product, options for replacing expensive fishmeal are key to conservation success. A variety of characteristics related to buche size and quality were affected by diet composition, but partial inclusion of soy protein as a substitute for fishmeal can produce buche of comparable quality to product grown from more expensive fishmeal diets. These findings highlight a path for diet changes to produce high value totoaba swim bladders from aquaculture at substantially lower costs.
... Fish swim bladdercommonly known as mawis among the most expensive dried seafood in China ( Fig. 1; [5,8]). Similar to other expensive seafood delicacies in the country, fish maw is linked to wealth, prestige and honor [5]. ...
... The fish is now rarely caught, but occasionally one is hooked and often makes headlines. In 2012, a single ~80 kg fish was sold for £300,000 [8,17]. The abundance of Chinese bahaba appears to be so low that it may be the first commercial marine species to become extinct in the wild [8]. ...
... In 2012, a single ~80 kg fish was sold for £300,000 [8,17]. The abundance of Chinese bahaba appears to be so low that it may be the first commercial marine species to become extinct in the wild [8]. ...
Article
The demand for fish maw (i.e., dried swim bladder) has apparently intensified during the past decades in Hong Kong and mainland China; currently, maw has similar annual import volumes but far higher mean unit values than other important seafood delicacies like shark fins and sea cucumber. Escalated demand for seafood delicacies can significantly contribute to the depletion of marine resources; yet a comprehensive understanding of maw value and the fisheries that supply it is lacking. We review available information on eight important maw-supplying species in major and largely undocumented source countries to examine the susceptibility and exposure of fisheries to the maw trade, which primarily serves Chinese demand. Comparing ex-vessel price ratios of maw to flesh (USD/kg), the overall mean price of maw can be as much as 72 times higher (range between 12:1 and 8389:1). Catch, price and export trends demonstrate that demand for maw is likely intensifying in countries already supplying it, shifting or expanding to new species, and emerging in new regions. We find that most maw-supplying species are under high fishing pressure, poorly or not protected. Those that yield the highest maw prices exhibit spawning aggregations, making them exceptionally vulnerable to overexploitation. While management interventions are needed to sustain fishery resources and capture economic benefits, their effectiveness will be challenged by the high value of maw.
... Sciaenids are extremely important to fisheries throughout their distribution (Chao, 2002;Froese and Pauly, 2019) and of great conservation concern, as many global populations are in spectacular decline (e.g. Cisneros-Mata et al, 1995;Sadovy and Cheung, 2003). Many sciaenids are estuary-dependent, either living year round in estuarine environments, or utilizing components of these environments for spawning, as nursery grounds or for feeding (Chao, 2002;Nelson, 2006). ...
... There are numerous examples which demonstrate overfishing of the spawning biomass, in combination with declines in freshwater inflow to key estuarine nursery habitats as a result of both anthropogenic and natural factors, has resulted in rapid population declines in sciaenid species globally (e.g. Cisneros-Mata et al, 1995;Ferguson et al., 2008;Griffiths, 1997;Lercari and Ch� avez, 2007;Musick et al., 2000;Sadovy and Cheung, 2003). Long-lived species with variable recruitment success, like A. japonicus, have evolved to have long reproductive lives so as to ensure population persistence through periods of relatively poor recruitment (Leaman and Beamish, 1984). ...
... Failure to take advantage of environmentally driven strong year class strengths will continue to inhibit any population recovery or subsequent fishery potential. In fact, long-term failure of the population to recover may ultimately lead to commercial extinction (Gould, 1972) or under the worst case scenario, potential biological extinction in the wild (Cisneros-Mata et al, 1995;Sadovy and Cheung, 2003). Clearly, the suite of biological, ecological and fishery characteristics that typify A. japonicus and many other sciaenid populations make them especially vulnerable to the combination of over-exploitation and environmental change (Sadovy and Cheung, 2003). ...
Article
Freshwater flows into estuaries influence fish populations through effects on recruitment, growth and mortality. We compared year class strength of a large sciaenid Argyrosomus japonicus with rainfall through a 16-year period in southeastern Australia, to understand the influence of freshwater input on this estuary-dependent and depleted population. Relative year class strength, estimated by back-calculating age composition data from commercial fishery landings, was positively related to rainfall within estuarine catchments (R² = 52%). Commercial estuarine landings from a separate 29-year dataset were positively related to rainfall two and three years earlier (R² = 21% and 44%, respectively). Year class strength of a key prey species, the penaeid prawn Metapenaeus macleayi, was also related to year class strength of A. japonicus (R² = 39%), suggesting that rainfall influences recruitment of A. japonicus by affecting food availability. Several years of above average rainfall may be required to promote recruitment substantial enough to rebuild the population.
... Overfishing and ocean pollution in the past decade have led to a dramatic decrease in fish in the wild fisheries of China (Liu & Sadovy 2008;Sadovy & Cheung 2003). The endemic species of giant yellow croaker (Bahaba taopongensos), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung 2003). ...
... Overfishing and ocean pollution in the past decade have led to a dramatic decrease in fish in the wild fisheries of China (Liu & Sadovy 2008;Sadovy & Cheung 2003). The endemic species of giant yellow croaker (Bahaba taopongensos), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung 2003). The spotted drum (Protonobea doacanthus) and large yellow croaker (Laromochthys crocea, which is endemic to East Asia and was once one of the three top commercial marine fishes in China), have been severely depleted throughout their geographic range since the 1980s and have now almost entirely disappeared from landings (Liu & Sadovy 2008;Sadovy & Cheung 2003). ...
... The endemic species of giant yellow croaker (Bahaba taopongensos), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung 2003). The spotted drum (Protonobea doacanthus) and large yellow croaker (Laromochthys crocea, which is endemic to East Asia and was once one of the three top commercial marine fishes in China), have been severely depleted throughout their geographic range since the 1980s and have now almost entirely disappeared from landings (Liu & Sadovy 2008;Sadovy & Cheung 2003). The most recent study of Indo-Pacific humpback dolphins (Sousa chonensos, locally called the Chinese white dolphin) biosonar activity in the Pearl River Estuary indicated that its diel, seasonal and tidal patterns might be ascribed to the spatial-temporal variability of its prey (Wang et al. 2015b); however, little attention has been paid to local fishes, with only sporadic fishery distribution data with poor temporal and spatial resolution obtained from 1986-1987 by bottom trawl and in 1998 by beam trawl and hang trawl (Li et al. 2000b;Wang & Lin 2006).The fine-scale distribution pattern of humpback dolphin prey has yet to be investigated. ...
Preprint
Full-text available
Background. Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species. Methods. Underwater biological sounds in the Pearl River Estuary, China, were collected using passive acoustic monitoring, with special attention paid to fish sounds. A total of 1408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine. Results. We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2600 Hz and a majority of the energy below 4000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times that were exclusive from each other, suggesting that they might be produced by different species. According to the literature, the two section signal types of 1+1 and 1+N 10 might belong to big-snout croaker ( Johnius macrorhynus ), and 1+N 19 might be produced by Belanger's croaker ( J. belangerii ). Discussion. Categorization of the baseline ambient biological sound is an important first step in mapping the spatial and temporal patterns of soniferous fishes. The next step is the identification of the species producing each sound. The distribution pattern of soniferous fishes will be helpful for the protection and management of local fishery resources and in marine environmental impact assessment. Since the local vulnerable Indo-Pacific humpback dolphin ( Sousa chinensis ) mainly preys on soniferous fishes, the fine-scale distribution pattern of soniferous fishes can aid in the conservation of this species. Additionally, prey and predator relationships can be observed when a database of species-identified sounds is completed.
... Overfishing and ocean pollution in the past decade have led to a dramatic decrease in fish in the wild fisheries of China (Liu & Sadovy, 2008;Sadovy & Cheung, 2003). The endemic species of giant yellow croaker (Bahaba taipingensis), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung, 2003). ...
... Overfishing and ocean pollution in the past decade have led to a dramatic decrease in fish in the wild fisheries of China (Liu & Sadovy, 2008;Sadovy & Cheung, 2003). The endemic species of giant yellow croaker (Bahaba taipingensis), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung, 2003). The spotted drum (Protonibea diacanthus) and large yellow croaker (Larimichthys crocea, which is endemic to East Asia and was once one of the three top commercial marine fishes in China), have been severely depleted throughout their geographic range since the 1980s and have now almost entirely disappeared from landings (Liu & Sadovy, 2008;Sadovy & Cheung, 2003). ...
... The endemic species of giant yellow croaker (Bahaba taipingensis), which is highly valued as a traditional medicine of its swim bladder and was an important fish stock before the 1960s, collapsed in the wild and was determined to be commercially extinct in 1997 (Sadovy & Cheung, 2003). The spotted drum (Protonibea diacanthus) and large yellow croaker (Larimichthys crocea, which is endemic to East Asia and was once one of the three top commercial marine fishes in China), have been severely depleted throughout their geographic range since the 1980s and have now almost entirely disappeared from landings (Liu & Sadovy, 2008;Sadovy & Cheung, 2003). The most recent study of Indo-Pacific humpback dolphins (Sousa chinensis, locally called the Chinese white dolphin) biosonar activity in the Pearl River Estuary indicated that its diel, seasonal and tidal patterns might be ascribed to the spatial-temporal variability of its prey (Wang et al., 2015b); however, little attention has been paid to local fishes, with only sporadic fishery distribution data with poor temporal and spatial resolution obtained from 1986 to 1987 by bottom trawl and in 1998 by beam trawl and hang trawl (Li, Chen & Sun, 2000;Wang & Lin, 2006). ...
Article
Full-text available
Background Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species. Methods Underwater biological sounds in the Pearl River Estuary, China, were collected using passive acoustic monitoring, with special attention paid to fish sounds. A total of 1,408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine. Results We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2,600 Hz and a majority of the energy below 4,000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times that were exclusive from each other, suggesting that they might be produced by different species. According to the literature, the two section signal types of 1 + 1 and 1 + N 10 might belong to big-snout croaker ( Johnius macrorhynus ), and 1 + N 19 might be produced by Belanger’s croaker ( J. belangerii ). Discussion Categorization of the baseline ambient biological sound is an important first step in mapping the spatial and temporal patterns of soniferous fishes. The next step is the identification of the species producing each sound. The distribution pattern of soniferous fishes will be helpful for the protection and management of local fishery resources and in marine environmental impact assessment. Since the local vulnerable Indo-Pacific humpback dolphin ( Sousa chinensis ) mainly preys on soniferous fishes, the fine-scale distribution pattern of soniferous fishes can aid in the conservation of this species. Additionally, prey and predator relationships can be observed when a database of species-identified sounds is completed.
... In cases such as these, fisheries reconstruction provides insight into unrecorded or unassessed human impacts (McClenachan & Kittinger, 2012;Pauly & Zeller, 2016;Zeller, Booth, Craig, & Pauly, 2006). Likewise, nontraditional data sources are a vital complement to scientific data for understanding long-term change and have often been incorporated in the understanding of data-poor fisheries, providing valuable insights into fisheries reconstruction, history, management and status that may otherwise not be available (Johannes, 1981;Kittinger et al., 2011;Sadovy & Cheung, 2004;Sáenz-Arroyo et al., 2006). ...
... Since older fishers worked in the early years of the commercial fishery-and in some cases as subsistence fishermen in the 1940s and 1950s-they witnessed what could be considered a historical baseline abundance level for these two locations. These observations are vital for future evaluations of conservation status, and carrying out this type of research while older expert fishers are alive is of prime importance(Johannes et al., 2000;Sadovy & Cheung, 2004; ...
Article
Evaluating historical changes in the exploitation of marine organisms is a key challenge in fisheries ecology and marine conservation. In the Eastern Pacific, marine turtles were exploited for millennia before systematic monitoring began <50 years ago. Using ethnographic and historical data, we generated a detailed reconstruction of the East Pacific green sea turtle (Chelonia mydas) fishery in Mexico's Baja California peninsula from 1700 to 1990. Sea turtles from the region's important feeding areas were a staple food source from the earliest phases of human occupation, dating back at least 12,000 years. In contrast with regions such as the Caribbean, small human populations and limited market access resulted in apparently sustainable turtle harvests until the second half of the 20th century. We found that the estimated annual catches between 1960 and 1980 exceeded the estimated annual catches of the previous 250 years by an order of magnitude, leading to the collapse of the fishery and the depletion of the green turtle population. A total ban on sea turtle captures in 1990, comprehensive nesting beach protection, and significant conservation efforts resulted in increases in breeding females on nesting beaches and catch rates in scientific monitoring on main feeding grounds since the early 2000s. This provides a positive outlook for this once-depleted population segment. Although further research is needed to evaluate current conservation status, we have identified a date, between 1950 and 1960, which can serve as a reliable temporal reference for future evaluations of historical baseline abundance in this region.
... It is possible that at least some of the positive signals in the measured indicators of A. japonicus in the present study could be attributed to angler learning and technology creep. Like other large sciaenids (Sadovy and Cheung 2003), A. japonicus forms large and predictable aggregations of adults, particularly around turbid estuary mouths, offshore pinnacles and wrecks. As time passes, anglers have learnt to predict these patterns and have become more effective at targeting large adult fish (Sadovy and Cheung 2003). ...
... Like other large sciaenids (Sadovy and Cheung 2003), A. japonicus forms large and predictable aggregations of adults, particularly around turbid estuary mouths, offshore pinnacles and wrecks. As time passes, anglers have learnt to predict these patterns and have become more effective at targeting large adult fish (Sadovy and Cheung 2003). Besides improvements in fishing tackle technology, the advent of several kinds of artificial lures (including weighted, lipped crankbaits and jig-head plastics), which are extremely effective at catching large A. japonicus, have likely contributed to the observed increase in maximum mass. ...
Article
Although marine recreational fisheries are socially and economically important, there is often limited funding for their monitoring and assessment. With South African anglers reporting catch declines for almost all targeted species and little long-term monitoring data available, novel methods need to be explored to provide managers with additional information. This study aimed to evaluate the efficacy of content analysis of print-media records for detecting long-term trends in species composition, size composition and distribution of selected recreational fishery species. Information for eight fishes captured in the marine shore-based fishery was collected from South Africa’s most popular recreational fishery magazine, between 1960 and 2009. During the five decades, there were shifts in the catch composition, from being dominated by slow-growing, large predators to faster-growing, large predators and lower-trophic-level species. There were no significant trends in the mean and maximum sizes of the dominant species, except for dusky kob Argyrosomus japonicus, which increased significantly in the maximum size reported during the study period. The distributional range of A. japonicus and leervis Lichia amia significantly increased, and that of galjoen Dichistius capensis significantly decreased. However, it was uncertain whether these trends could be attributed to population changes, changes in angler technology and/or behaviour, or climate signals. Overall, this type of content analysis may provide a cost-effective method to examine changes in species composition and fish distributions over time, but, without detailed knowledge of shifts in angler behavioural patterns, it may not be as useful for understanding changes in the population dynamics of recreational fishery species. It is suggested that fishery-independent monitoring programmes are most suited for this type of complex fishery.
... Sciaenid species are globally distributed and comprise one of the most important groups of fish, supporting many commercial and recreational fisheries worldwide (Fisher et al., 1981;Griffiths & Hecht, 1995a, 1995bOlsen et al., 2018;Paxton & Eschmeyer, 1994;Silberschneider & Gray, 2005). Unfortunately for many species, a lack of life history information during fishery exploitation, coupled with slow growth, late size and age at maturity, and spawning aggregations increasing susceptibility to large catches, has led to a severe depletion of many sciaenid stocks (Sadovy & Cheung, 2003). ...
... The large sizes attained by many species within the family make them highly prized and targeted within recreational and commercial fisheries (Sadovy & Cheung, 2003). Reaching sexual maturity at large sizes also results in a predisposed risk to overfishing and significant declines during the last few decades have been reported for several species e.g. ...
Article
Worldwide there have been declines in stocks of exploited sciaenids. Despite a long history of exploitation, there has been no study of the life history characteristics of the fishery‐important sciaenid, teraglin, Atractoscion atelodus. This study describes the reproductive characteristics of A. atelodus within the major area of its distribution and fishery, New South Wales (NSW) Australia. Characteristics studied included the size and age at maturity, fecundity, spawning mode and season, and these are compared to congeneric species. Atractoscion atelodus displays year‐round batch spawning behaviour with asynchronous oocyte development and indeterminate fecundity. This is unusual for sciaenids, which typically display spring‐summer spawning and only over a few months. The length and age at which 50% of the population matures for both males and females is 36 cm fork length (FL) and 1 year, a smaller size compared to other closely related sciaenids. While the species displays resilient reproductive characteristics such as protracted year‐round spawning, constant supply of vitellogenic oocytes and relatively small/young age at maturity, there are also characteristics that make it susceptible to over‐exploitation. These include highly female skewed sex ratios, as well as their schooling and voracious feeding behaviour leading to the potential for high catch rates.
... Because the Upper Gulf is the only known spawning site, this species is highly vulnerable to overfishing and potential collapse (Erisman et al., 2012). The history of collapses in fisheries elsewhere in the world that have targeted the spawning migrations of large-bodied sciaenids is well known (Sadovy and Cheung, 2003;Erisman et al., 2012). Illegal fishing (poaching) remains a serious concern in the Northern Gulf, where an estimated 86-90% of Gulf corvina catch and 62% of the total fisheries catch takes place in marine protected areas (Erisman et al., 2012;Rodríguez-Quiroz et al., 2012). ...
... Like many other exploited fishes, their vulnerability to capture is exacerbated by their behavior of forming large, predictable spawning aggregations at restricted locations Sadovy and Erisman, 2010). Most workers have considered unregulated/unenforced fishing to be the primary threat to stock numbers of these and other exploited fishes (Cisneros-Mata et al., 1995;Román-Rodríguez, 1990Musick et al., 2000;Sadovy and Cheung, 2003;Rodríguez-Quiroz et al., 2010;Erisman et al., 2012;Chao et al. n.d;Valenzuela-Quiñónez et al., 2015;IUCN online). Aragón-Noriega et al. (2009) analyzed historical fishing data for another sciaenid, the Gulf (or bigeye) croaker (Micropogonias megalops), in the Upper Gulf. ...
Article
A review of published research indicates that the Northern Gulf of California is, historically and currently, one of the most biologically productive marine regions on Earth. This high productivity is driven by a unique mix of factors, including: coastal upwelling, wind-driven mixing, extreme tidal mixing and turbulence, thermohaline circulation that moves intermediate waters into the mixed layer, coastal-trapped waves, regular sediment resuspension, and, to a lesser extent, agricultural runoff, released nutrients from erosion of ancient Colorado River Delta sediments, and perhaps input from decomposing tidal-flat plant debris. It has been suggested that decreased Colorado River flow, due to anthropogenic water impoundments and diversions, has had a negative impact on the health of the Northern Gulf of California ecosystem, particularly by reducing primary productivity and/or stock production of finfish and shellfish. However, there is no evidence that surface flow from the Colorado River is now, nor has ever been an important driver of primary productivity in the Northern Gulf, and nutrient/chlorophyll studies show no relationship to Colorado River flow (or, if anything, reduced nutrient/chlorophyll levels occur during high river-flow periods). And, there is very limited and equivocal evidence to support the claim that reduced river flow has significantly impacted secondary productivity in the Northern Gulf. The marine ecosystem of the Northern Gulf remains rich in nutrients, high in biodiversity and productivity, and appears to continue to be healthy, except for the impacts of historical and current fisheries. Human extraction of shrimp, Gulf corvina, totoaba (largely illegally), and other marine resources, remain very high in this region. There also is no evidence that reduced Colorado River flow has negatively impacted the health of the critically endangered vaquita porpoise, and assertions that it has done so deflect attention from the actual cause of decline—bycatch in legal and illegal gillnet fisheries. A review of Colorado River Delta research confirms that, historically and perhaps as long as the river has reached the Gulf of California, there have been long periods of no flow, or greatly reduced flow to the sea. Thus, the ecosystem is historically adapted to broadly fluctuating river flows and elevated salinities. Although commonly used by recent researchers, measurements of Colorado River water crossing the border into Mexico do not provide a reliable proxy for how much water (if any) actually reaches the Upper Gulf because of the complex nature of internal basins and diversions in the region.
... Most of the species are targeted by local fisheries and their global fishery production in the past two decades is around one million ton per year [14]. However, many sciaenid species are vulnerable to overfishing [15][16][17][18][19][20] and habitat degradation [18,21,22]. In 2007, the IUCN-Species Survival Commission identified this family as a conservation priority and called for the urgent establishment of a Sciaenidae Red List Authority to assess the risk of extinction of all sciaenid species and to recommend actions needed for the next decade to ensure their well-being [23]. ...
Article
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The family Sciaenidae, known as croakers or drums, is one of the largest perciform fish families. A recent multi-gene based study investigating the phylogeny and biogeography of global sciaenids revealed that the origin and early diversification of this family occurred in tropical America during the Late Oligocene—Early Miocene before undergoing range expansions to other seas including the Indo-West Pacific, where high species richness is observed. Despite this clarification of the overall evolutionary history of the family, knowledge of the taxonomy and phylogeny of sciaenid genera endemic to the Indo-West Pacific is still limited due to lack of a thorough survey of all taxa. In this study, we used DNA-based approaches to investigate the evolutionary relationships, to explore the species diversity, and to elucidate the taxonomic status of sciaenid species/genera within the Indo-West Pacific clade. Three datasets were herein built for the above objectives: the combined dataset (248 samples from 45 currently recognized species) from one nuclear gene (RAG1) and one mitochondrial gene (COI); the dataset with only RAG1 gene sequences (245 samples from 44 currently recognized species); and the dataset with only COI gene sequences (308 samples from 51 currently recognized species). The latter was primarily used for our biodiversity exploration with two different species delimitation methods (Automatic Barcode Gap Discovery, ABGD and Generalized Mixed Yule Coalescent, GMYC). The results were further evaluated with help of four supplementary criteria for species delimitation (genetic similarity, monophyly inferred from individual gene and combined data trees, geographic distribution, and morphology). Our final results confirmed the validity of 32 currently recognized species and identified several potential new species waiting for formal descriptions. We also reexamined the taxonomic status of the genera, Larimichthys, Nibea, Protonibea and Megalonibea, and suggested a revision of Nibea and proposed a new genus Pseudolarimichthys.
... feeding protocol, larval diet, length growth, live prey, survival, treatment 1 | INTRODUCTION Meagre (Argyrosomus regius Asso, 1801) has been proposed as one of the most promising candidates for marine finfish diversification on commercial aquaculture in Mediterranean and Eastern Atlantic coasts (Mateos, 2007). It is highly fecund (Sadovy & Cheung, 2003) and fast growing (Gil, Grau, Basilone, Ferreri & Palmer, 2013) and presents good food conversion ratios (Jim enez, Pastor, Grau, Alconchel & C ardenas, 2005). There has also been increasing interest in studying meagre for restocking the depleted natural population (Gil, Palmer, Grau & P erez-Mayol, 2014). ...
Article
In hatcheries, meagre Argyrosomus regius larvae still depend on an adequate supply of rotifers and Artemia, as no artificial diet can totally fulfil their nutritional requirements. However, production of live feed is highly expensive and demands intensive labour and specific facilities. This study investigated the effect of a dietary regime without the use of rotifers, to simplify the meagre larval rearing protocol. Two feeding treatments (T1 & T2) are compared to investigate their effects on survival and growth of meagre larvae. In T1, larvae were fed rotifers from 2 to 5 days post hatch (dph), and Artemia from 4 to 15 dph. In T2, larvae were kept under dark conditions and fed Artemia from 6 to 15 dph. Standard larval length (SL) was significantly higher in T1 (p < .01) until 8 dph in comparison with larvae reared initially without rotifers. No significant difference in SL was found among treatments (p = .187) at 15 dph. Significant difference was found among treatments in survival rate at 15 dph (p < .003). The survival rate observed at 15 dph in T2 (30 ± 4.2%) represents an important finding, although the highest survival rate was observed in T1 (45.0 ± 3.4%). This study showed that it is possible to conduct larval rearing of meagre without using rotifers. Nevertheless, further research efforts are still needed to improve these results in comparison with the common larval rearing protocol.
... Certain types of medicine can become so popular, sometimes spreading outside the region in which they were initially used, that the extraction of the raw material from the wild becomes an impediment to biodiversity conservation. It has been noted that some of the lesser known and smaller species can be negatively affected by the trade for traditional medicine (Sadovy and Cheung, 2003;Nijman et al., 2012a;Humle and Konate, 2015;Byard, 2016;Rowley et al., 2016). Reptiles (including turtles, tuataras, lizards, snakes, and crocodiles) are widely used in folk and traditional medicine (Zhou and Jiang, 2004;Alves et al., 2008Alves et al., , 2009Magnino et al., 2009;Segniagbeto et al., 2013), and there are numerous examples in which their use has led to the decline of species (Gong et al., 2009;Nijman et al., 2012a, b;Caillabet, 2013). ...
Article
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Reptiles are traded globally for medicinal purposes. Historic qualitative accounts of reptiles used as medicine in Morocco are numerous, but contemporary quantitative data are rare. In 2013-2014, we surveyed 49 wildlife markets in 20 towns throughout Morocco, plus the Spanish exclaves of Ceuta and Melilla. We recorded 1,586 specimens of at least nine species for sale in 14 of the Moroccan markets with a combined value of about US $100,000. The most prominent markets were those in Marrakesh, Meknes, Casablanca, and Fez, with the former two cites trading equal quantities of dried and live specimens and the latter two trading mainly dried specimens. Common species were the Med-iterranean chameleon (Chamaeleo chamaeleon) with 720 specimens (506 dried, 214 alive) and the Bell's Dabb lizard (Uro-mastyx acanthinura) with 428 specimens (247 dried, 181 alive), both traded in 10 markets, and spur-thighed tortoise (Testudo graeca; 57 carapaces), for sale in eight cities. Over 200 African rock python (Python sebae) skins were identified and may have been illicitly imported from other parts of Africa. The turnover of Mediterranean chameleon and Bell's Dabb lizard specimens after four weeks as measured by repeat surveys was 66% for both species, resulting in an estimated annual turnover of 1,520 chameleons (range 921–2,303) and 775 lizards (range 364–1,174). Despite legal protection and regulations locally within Morocco and internationally through CITES, reptiles are commonly and openly traded for medicinal purposes throughout Morocco. However, traders are not forthcoming in conveying the legal status of these species and restrictions on trade to potential buyers. Increased enforcement of existing wildlife protection legislation is needed to prevent this exploitation from the illegal wildlife trade that could negatively impacts imperiled species.
... Controversial ideas on the recovery of the totoaba stock have been expressed [30][31][32][33][34][35], as releases of water across the border in excess of agricultural usage will probably have a positive impact upon endangered species habitat [36]. The delta of the Colorado River is not dead, but it requires international collaboration for its recovery [16]. ...
... Fish maw (Fig. 1b) is the commercial term for dried swim bladders of large fish, such as croaker and sturgeon. The scale of fish maw production in Southeast Asia is quite large, particularly in Hong Kong and Southern China [1][2][3]. Fish maw is traditional Asian food delicacies and has been used as medicines and tonics in China and Southeast Asia for many centuries. Some traditional medical properties ascribed to fish maw include improving amnesia, insomnia, dizziness, anepithymia and weakness [4]. ...
Article
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The swim bladder of fish is an internal gas-filled organ that allows fish to control their buoyancy and swimming depth. Fish maws (the dried swim bladders of fish) have been used over many centuries as traditional medicines, tonics and a luxurious gourmet food in China and Southeast Asia. Little is known about the structural information of polysaccharides comprising this important functional material of fish tissue. In the present study, the total glycosaminoglycan (GAG) from fish maw was characterized. Two GAGs were identified, chondroitin sulfate (CS, having a molecular weight of 18–40 kDa) and heparan sulfate (HS), corresponding to 95% and 5% of the total GAG, respectively. Chondroitinase digestion showed that the major CS GAG was composed of ΔUA-1 → 3-GalNAc4S (59.7%), ΔUA-1 → 3-GalNAc4,6S (36.5%), ΔUA-1 → 3-GalNAc6S (2.2%) and ΔUA-1 → 3-GalNAc (1.6%) disaccharide units. 1H–NMR analysis and degradation with specific chondroitinases, both CS-type A/C and CS-type B were present in a ratio of 1.4:1. Analysis using surface plasmon resonance showed that fibroblast growth factor (FGF)-2 bound to the CS fraction (KD = 136 nM). These results suggest that this CS may be involved in FGF-signal pathway, mediating tissue repair, regeneration and wound healing. The CS, as the major GAG in fish maw, may have potential pharmacological activity in accelerating wound healing.
... Fish maws have been commonly recommended and consumed as delicacies, medicine and tonics in Asia over many centuries because their high nutritional value and they are believed to have some traditional medical properties, particularly in winter, as a tonic for those recovering form, attempting to ward off illness and for women after child delivery. Fish maws are commonly produced from croaker, with other species, such as eels, sea catfish and perch species (Clarke, 2004;Sadovy & Cheung, 2003;Wen et al., 2016). Recently, a kind of fish maw has sold on the market (Fig. 1). ...
... There have been approaches in the fisheries literature to reconstruct baselines of fish stocks using historical resources to document declines that were much greater than previously understood (Rosenberg et al., 2005). Additionally, fishers' ecological knowledge has been used to estimate the baselines of various fish stocks and fisheries (e.g., Sadovy & Cheung, 2003;Teh et al., 2007;Eddy, Gardner & Pérez-Matus, 2010). Kleypas & Eakin (2007) surveyed reef scientists to measure their opinions about the relative importance of different threats to coral reef ecosystems. ...
Article
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Coral reefs are important habitats that represent global marine biodiversity hotspots and provide important benefits to people in many tropical regions. However, coral reefs are becoming increasingly threatened by climate change, overfishing, habitat destruction, and pollution. Historical baselines of coral cover are important to understand how much coral cover has been lost, e.g., to avoid the ‘shifting baseline syndrome’. There are few quantitative observations of coral reef cover prior to the industrial revolution, and therefore baselines of coral reef cover are difficult to estimate. Here, we use expert and ocean-user opinion surveys to estimate baselines of global coral reef cover. The overall mean estimated baseline coral cover was 59% (±19% standard deviation), compared to an average of 58% (±18% standard deviation) estimated by professional scientists. We did not find evidence of the shifting baseline syndrome, whereby respondents who first observed coral reefs more recently report lower estimates of baseline coral cover. These estimates of historical coral reef baseline cover are important for scientists, policy makers, and managers to understand the extent to which coral reefs have become depleted and to set appropriate recovery targets.
... According to the Chinese beliefs and legends, the swim bladder is an aphrodisiac product. The Bahaba's swim bladder can reach a price of $20,000 (Sadovy and Cheung, 2003). The value of a totoaba bladder, according to the fishermen of Golfo de Santa Clara, can be between 4,000 and 5,000 dollars, but a bladder of more than 2 kg can be traded on the black market for up to 9,000 dollars. ...
Chapter
Marine spatial planning (MSP) is key for managing concurrent use in marine protected areas such as biosphere reserves. The success of MSP is highly dependent on the involvement of local communities in management decisions. However, land planning policies also have to be coherent with MSP. In this chapter, we analyse the case study of the Upper Gulf of California which holds several protection figures; among them, it was declared as a biosphere reserve. We review the history of this region in order to explain the key principles of MSP that have not been applied and that are the cause of the current conflicts. The transboundary approach has failed, mainly due to inadequate land use policies that have favoured an intensive use of the Colorado River freshwater resources. Local communities have not been involved in management decisions despite their dependence on fishing. Partial solutions have been adopted that have increased the conflict among fishermen due to their different origins, and indigenous (Cocopah) and non-indigenous (Golfo de Santa Clara fishermen) populations. Protection policies of Totoaba macdonaldi and Phocoena sinus (vaquita marina) have blamed fishermen for the fragile state of conservation of these species, obviating environmental factors. As a result, the social conflict is about to burst while minimum actions focus on land planning consequences.
... This collapse slowed the rate of increase of world fisheries in the 1970s (Muck 1989;FAO 2010). Other globally or regionally known examples of fishery collapses are Atlantic cod [Gadus morhua (Linnaeus, 1758)], Chinese bahaba [Bahaba taipingenese (Herre, 1932)] and the large yellow croaker [Larimichthys crocea (Richardson, 1846)], all of which are primarily due to the overfishing of spawning and/or over-wintering grounds (Walters and Maguire 1996;Sadovy and Cheung 2003;Liu and Sadovy de Mitcheson 2008). Fluctuations in the abundance of Anchoveta and other species provided the opportunity for global fisheries to reach further peaks in the late-1980s and mid-1990s (FAO 2010). ...
Article
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China (excluding Hong Kong, Macao and Taiwan, unless specified) is the greatest contributor to the total catch of global marine fisheries. As such, data about the degrees of exploitation and developmental dynamics of its fisheries are essential to evaluate and guide future sustainable seafood production and policy implementation and adjustments. In this study, we summarized the national official statistic data on domestic marine fisheries (including both marine capture fisheries and mariculture) from the earliest available year, 1950, to the latest year, 2014, using on the China Fishery Statistical Yearbooks. We also conducted analyses to understand the historical and current statuses of Chinese marine fisheries and their developmental trends. Domestic marine capture fisheries are declining and will continue to decline because of the current degradation and loss of coastal habitats, mainly due to coastal development and pollution and the over-exploitation of coastal natural resources. In contrast, mariculture has demonstrated promise as an approach to increase seafood production. However, given the wide latitudinal range of domestic seas in China, global climate change may impact China’s marine natural resources. We highlight that effective management measures and long-term monitoring are essential for the sustainability of domestic marine capture fisheries. Moreover, environmentally-friendly practices in mariculture should be enhanced and species introduction carefully monitored to achieve sustainable development. © 2018 Springer International Publishing AG, part of Springer Nature
... Our observations indicate no positive relationship between female size and reproductive value, rendering gear restrictions to reprieve larger fish unsuitable. Taking into account the observed reproductive tactics, time and area closures may be more promising to conserve the stock's reproductive potential and to warrant sustainability (Sadovy & Cheung 2003. In the case of E. fimbriata's stock in southern Senegalese waters, this would imply halted fishing activities at the coast from February to May, at the estuary's mouth from April to June, and inside the system's middle reaches from September to November. ...
Thesis
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Marine fishes employ specialized reproductive tactics in response to hydrographic fluctuations in their spawning habitats. Unprecedented environmental conditions induced by climate change will challenge these behavioral and physiological adaptations. Taking into account the key drivers of stock productivity, this work aimed at assessing the reproductive adaptations of a clupeid fish species, Ethmalosa fimbriata, towards hydrographic alterations in its spawning habitats: the upwelling area at the Senegalese South Coast and the inverse hypersaline Sine Saloum estuary. Obtained results show that E. fimbriata's is adapted towards increasing its reproductive investment at high water temperatures (26 - 30°C) and at salinities (42 - 51), which by far exceed marine conditions, in an effort to maximize recruitment success. Examination of oocyte fatty acid profiles revealed that oocytes spawned inside the estuary under these high temperature/high salinity conditions were likely to develop normally. Investigation of spawning energetics and otolith micro-chemistry evidenced distinct stock spawning components, which are characterized by delimited home ranges and specific productivity. Because of this complex stock structure and by employing auspicious reproductive tactics the species is so far likely to benefit from the severe impacts of climate change on its spawning habitat. The adaptations described herein potentially allow for out-competing other pelagic fish species with lower adaptive potential. All in all, high plasticity in reproductive traits combined with high fecundity and small generation times in clupeid fishes such as E. fimbriata may lead to an enhanced fitness during rapid environmental changes.
... Less productive components; i.e., E. fimbriata's neritic sub-population, are more likely to become overexploited and a decline in catch rates could ultimately compromise the fisheries' activity and affect the depending socioeconomic sector. In order to preserve reproductive potential over the stock's full geographical range, specialized management approaches such as spatially variable time closures are recommended Sadovy & Cheung, 2003). ...
Article
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The gross energy content of spawning batches and the microchemistry of sagittal otoliths in individual female bonga shad Ethmalosa fimbriata were compared between contrasting sampling sites at the Senegalese southern coast and inside the hypersaline Sine Saloum Estuary. Results show that females spawning in the estuary's middle reaches invested almost three times more energy into reproduction (115 ± 65 J g−1 body mass) than their neritic counterparts (39 ± 34 J g−1 body mass). Also, female otolith levels of Ba:Ca, Sr:Ca and Zn:Ca either differed significantly between study sites or could be linked to heterogeneous environmental variables. A quadratic discriminant function analysis provided evidence of segregated spawning populations of E. fimbriata in southern Senegalese waters.
... Marine fisheries resources worldwide have been managed based on conventional data-intensive approaches of fisheries biology for decades. However, many of them, especially for coastal regions, experienced failures in conservation and sustainable use, mainly because the approaches failed to consider all the complexity and uncertainty of socioecological systems or the required extensive datasets were not available [1][2][3][4]. Utilization of local ecological knowledge (LEK) was thus advocated as one of the alternative approaches, considering that successful coastal management has been implemented for centuries by many coastal societies based on sound ecosystem reasoning and application of locally-plausible effort control and habitat protections measures, without "scientific data" [4][5][6][7]. LEK refers to the knowledge that local or indigenous people have developed as they adapted to their living environment. ...
Article
The use of local ecological knowledge (LEK) has been advocated for coastal ecological and environmental resource management (EERM), noting that successful management on the resources has been implemented for centuries by many coastal societies based on their LEK. However, changes in LEK are observed in many instances worldwide and have caused impacts on the EERM. This study reports industry-, government- and culture-driven changes of a LEK and the impacts of the changes on the environment. Taking the Tao of Taiwan's Orchid Island as an example, the connotations and trend of their flyingfish culture are analyzed. Specifically, the five conditions for achieving effective EERM established by Dietz et al. (2003) are used as the theoretical basis to analyze the impact of LEK changes on environmental change. The findings indicated that this culture complies with the conditions proposed and proved that application of the flyingfish culture to the management of Orchid Island's marine and fishery resources has its theoretical basis and advantages. However, the flyingfish culture was found to be facing major changes which has violated the conditions for effective management of shared resources. Various external factors have contributed to the changes in the flyingfish culture. These include the impacts of inappropriate government policies, modern science and technology, education, and the market economy. Especially, inappropriate policies have reduced the integrity of the flyingfish cultural landscape, incentivized the use of motorized boats, commodified the flyingfish, and expanded the market for related products. Some suggestions for managing the changes to the culture are proposed.
... Other rare species directly provide services with a marginal value that increases as abundance decreases, (i.e., with scarcity value; Figure 1B, Box 1) [41,42]. Examples include rare species harvested for luxury goods (e.g., sturgeons for caviar [51]), targeted for trophy hunting [52], used for traditional medicine [53], and collected as ornamental species or exotic pets [41] (Box 1). Unlike Category 1, the high value from rarity here can compromise the persistence of these species rather than promote their conservation, without well-defined, secure property rights [41,42]. ...
Article
Conservation aims to preserve species and ecosystem services. If rare species contribute little to ecosystem services, yet are those most in need of preservation, tradeoffs may exist for these contrasting objectives. However, little attention has focused on identifying how, when, and where rare species contribute to ecosystem services and at what scales. Here, we review distinct ways that ecosystem services can positively depend on the presence, abundance, disproportionate contribution or, counterintuitively, the scarcity of rare species. By contrast, ecosystem services are less likely to depend on rare species that do not have a unique role in any service or become abundant enough to contribute substantially. We propose a research agenda to identify when rare species may contribute significantly to services.
... This is of concern because large bodied sciaenids are particularly vulnerable to overexploitation (e.g. Bahaba taipingensis, Sadovy and Cheung, 2003;Totoaba macdonaldi, Lercari and Chávez, 2007;Valenzuela-Quiñonez et al., 2015;Argyrosomus coronus, Potts et al., 2010;A. japonicus, Ferguson et al., 2014;Pogonias cromis, Chao et al., 2015). ...
Article
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The Acoupa weakfish Cynoscion acoupa (Lacepède, 1801) is a large inshore sciaenid of commercial and social importance found along the entire Brazilian coast. In spite of this, there is few information on the species, both in terms of biological aspects and fishery yields, particularly off southeastern Brazil. Within this context, this study aimed to an evaluation of Acoupa weakfish fishery production off São Paulo coast (23°22'-25°18'S) based on publicly available statistical data collected between 1998 and 2016. Acoupa weakfish fishery in this State takes place on both industrial and artisanal scales, and employs at least 22 different fishing gears. The pair-trawling fishery was the most important Acoupa weakfish producer during the period surveyed, with a sharp decline in the catches from 2007 onward due to the establishment of Marine Protected Areas off São Paulo coast, which banned trawling in depths shallower than 26 meters. Acoupa weakfish yields were relatively low in São Paulo when compared with other demersal fishes exploited, despite the high retail prices commanded by the species in regional markets and restaurants.
... The EU began to deal with deep-sea fisheries in 1992, as a result of assessments carried out by the International Council for the Exploration of the Sea (ICES), who stated that most of the deep-water species of commercial interest were overfished [28]. The current scientific evidence suggests that many deep-sea fish stocks are being exploited beyond sustainable levels [23,[29][30][31][32], thus emphasising the need to improve the management of these species [3,[32][33][34][35]. ...
Article
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As part of the “Innovations in the Food System: Exploring the Future of Food” Special Issue, this paper briefly reviews studies that highlight a link between deep-sea fishery resources (deep-sea food resources) and vulnerable marine ecosystems (VME), species, and habitats in the Mediterranean Sea, providing new insights into changes in commercial and experimental catches of the deep-sea fishery resources in the central Mediterranean over the last 30 years. About 40% of the total landing of Mediterranean deep-water species is caught in the central basin. Significant changes in the abundance of some of these resources with time, sea-bottom temperature (SBT), and fishing effort (FE) have been detected, as well as an effect of the Santa Maria di Leuca cold-water coral province on the abundance of the deep-sea commercial crustaceans and fishes. The implications of these findings and the presence of several geomorphological features, sensitive habitats, and VMEs in the central Mediterranean are discussed with respect to the objectives of biodiversity conservation combined with those of management of fishery resources.
... Species within the family Sciaenidae support many significant commercial and recreational fisheries worldwide (Froese & Pauly, 2019) and are highly prized owing to the large sizes they attain (Sadovy & Cheung, 2003). Numerous species (Sciaenops ocellatus, Ross et al., 1995;Argyrosomus japonicus, Silberschneider & Gray, 2005; Totoaba macdonaldi, Potts et al., 2010; Argyrosomus inodorus, Griffiths, 1997; Atractoscion nobilis Hervas et al., 2010) have experienced substantial declines in fishery landings because of the large size that sexual maturity is reached. ...
Article
Growth rates and other age-related population characteristics are essential parameters underpinning management of a stock. This is the first study to estimate length-at-age of Atractoscion atelodus (family Sciaenidae) in New South Wales (NSW), despite the species being exploited since the 1940’s. The aim of the current study was to quantify the age-based biological characteristics of A. atelodus and in particular: (i) validate the use of sagittal otoliths to quantify age; (ii) estimate the growth rates and longevity of males and females; (iii) examine geographical variation in age and growth; (iv) document the age composition in commercial landings; and, (v) estimate mortality rates. Atractoscion atelodus is relatively fast growing, reaching 40 cm fork length (FL) in the first year of life and living to at least 14 yr. Growth was significantly different between sexes, with modelled asymptotic lengths of females (L∞=84.6 cm FL) greater than males (L∞=69.0 cm FL). Growth rates were also significantly different between northern and southern populations. Fish sampled from the southern region were younger and faster growing than those sampled in the northern region, supporting the counter-gradient growth theory and the influence of upwelling providing greater nutrient and food availability. The commercial fishery was predominantly based on young fish < 3 yr with few (~5%) greater than 5 yr. Fishing mortality estimates (F=0.42) were similar to natural mortality estimates (M=0.44). The age-based parameters estimated in the present study suggest that A. atelodus should be relatively resilient to fishing; however, the sizes and ages in landings are indicative of a stock heavily fished. The fishery is experiencing truncated age distributions and appears to be largely recruitment driven, increasing susceptibility to Overexploitation. Determining geographical differences in growth rates of a population has important implications when considering impacts of anthropogenic drivers such as global warming and over-exploitation and is important to determine in managing exploited fish populations. This article is protected by copyright. All rights reserved.
... Au début du XXIe siècle, le principal problème qui s'est posé était celui de la production (Jiménez et al., 2005). Plusieurs auteurs ont également souligné l'importance de développer la culture de maigre à des fins de conservation en raison du recul que ses populations ont accusé dans les zones méditerranéennes (Quero, 1989), dû à la pression de pêche, la contamination et la dégradation de ses zones de pontes et alevinages (Sadovy & Cheung, 2003). ...
Thesis
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... Dans ce sens, les espèces de grandes tailles sont donc plus facilement affectées car plus susceptibles d'être pêchées et aussi plus vulnérables car leur cycle biologique est plus long. En effet, les espèces les plus grandes ont besoin de plus de temps pour atteindre la maturité sexuelle et se reproduire (Denney et al., 2002) ce qui les rend d'autant plus sensibles à la surpêche (Sadovy and Cheung, 2003). Si le seuil critique est dépassé et le stade de surpêche atteint, la population n'est plus exploitable au risque de la voir disparaitre totalement. ...
Thesis
Dans le contexte actuel de surpêche et de réchauffement climatique, il est nécessaire d’adopter une gestion écosystémique des ressources halieutiques. Ce travail de thèse apporte des éléments de réponse à cette problématique en se penchant sur le cas de la pêcherie crevettière guyanaise et de son impact sur les communautés de poissons associées. Comme dans la plupart des régions tropicales, les eaux côtières de Guyane se sont réchauffées d’environ 1°C entre 1990 et 2017. En revanche, comme dans peu d’endroits au monde, la pression de pêche s’est quasiment effondrée sur cette même période. Ce cas d’étude est donc une bonne opportunité pour comprendre la réaction des communautés de poissons de cette région tropicale après une diminution progressive et à grande échelle de la pression de pêche dans un contexte de réchauffement climatique. Les résultats de ce travail montrent que les facteurs environnementaux jouent un rôle dominant dans la structuration des communautés de poissons marins en Guyane. Les analyses montrent notamment des augmentations de certains indicateurs de diversité, une augmentation du spectre des tailles maximales théoriques des espèces et une augmentation de la redondance fonctionnelle qui est un facteur clé pour la stabilité des peuplements. Ces éléments témoignent d’une restructuration des communautés et mettent en avant leur capacité à retrouver un état riche et stable en une période relativement courte d’une douzaine d’années voire moins. On observe néanmoins une tropicalisation des communautés qui pose des questions sur l’évolution future de la diversité des écosystèmes tropicaux au regard des différents scénarios climatiques.
... Totoaba is currently listed as critically endangered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora and the International Union for Conservation of Nature and is listed under the U.S. Endangered Species Act and the Mexican norm for threatened species (NOM-059-SEMARNAT-2010), which includes species considered at risk of extinction (Scientific Authority CITES Mexico 2001;DOF 2010;Valenzuela-Quiñonez et al. 2015). A recent increase in the illegal harvest of totoaba is a consequence of the near extinction of the yellow croaker or Chinese bahaba (Bahaba taipingenisis) in China (Sadovy & Cheung 2003). The dried swim bladders of totoabas and bahabas are similar in size and appearance and can garner prices from US$1,500 to US$20,000/kg dried on the black market in China (CITES 2016; Cisneros-Mata et al. 2020). ...
... The statistical approaches used to infer extinctions are typically based on time series of sightings data, which are difficult to obtain for wide-ranging species, particularly marine fishes (10,11). As a consequence, marine extinctions have been overlooked, as many marine populations have been exploited to the point of collapse long before monitoring began (9,12,13). ...
Article
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Extinctions on land are often inferred from sparse sightings over time, but this technique is ill-suited for wide-ranging species. We develop a space-for-time approach to track the spatial contraction and drivers of decline of sawfishes. These iconic and endangered shark-like rays were once found in warm, coastal waters of 90 nations and are now presumed extinct in more than half (n = 46). Using dynamic geography theory, we predict that sawfishes are gone from at least nine additional nations. Overfishing and habitat loss have reduced spatial occupancy, leading to local extinctions in 55 of the 90 nations, which equates to 58.7% of their historical distribution. Retention bans and habitat protections are urgently necessary to secure a future for sawfishes and similar species. Available at: https://advances.sciencemag.org/content/7/7/eabb6026
... The global demand for marine animal products such as shark fins (Clarke et al., 2006), swim bladders (Sadovy and Cheung, 2003;Clarke, 2004), and ray gill plates (White et al., 2006;Ward-Paige et al., 2013) is unsustainable (Berkes et al., 2006;Lenzen et al., 2012). Particularly for the slower life history species has the intense fishing exploitation that targets these demands resulted in population declines and increased risks of extinction, sometimes with synergistic effects of environmental conditions (Jennings et al., 1999;Schindler et al., 2002). ...
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Understanding why different life history strategies respond differently to changes in environmental variability is necessary to be able to predict eco-evolutionary population responses to change. Marine megafauna display unusual combinations of life history traits. For example, rays, sharks and turtles are all long-lived, characteristic of slow life histories. However, turtles also have very high reproduction rates and juvenile mortality, characteristic of fast life histories. Sharks and rays, in contrast, produce a few live-born young, which have low mortality rates, characteristic of slow life histories. This raises the question if marine megafaunal responses to environmental variability follow conventional life history patterns, including the pattern that fast life histories are more sensitive to environmental autocorrelation than slow life histories. To answer this question, we used a functional trait approach to quantify for different species of mobulid rays, cheloniid sea turtles and carcharhinid sharks – all inhabitants or visitors of (human-dominated) coastalscapes – how their life history, average size and log stochastic population growth rate, log(λs), respond to changes in environmental autocorrelation and in the frequency of favorable environmental conditions. The faster life histories were more sensitive to temporal frequency of favourable environmental conditions, but both faster and slower life histories were equally sensitive, although of opposite sign, to environmental autocorrelation. These patterns are atypical, likely following from the unusual life history traits that the megafauna display, as responses were linked to variation in mortality, growth and reproduction rates. Our findings signify the importance of understanding how life history traits and population responses to environmental change are linked. Such understanding is a basis for accurate predictions of marine megafauna population responses to environmental perturbations like (over)fishing, and to shifts in the autocorrelation of environmental variables, ultimately contributing toward bending the curve on marine biodiversity loss.
... Totoaba is currently listed as critically endangered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora and the International Union for Conservation of Nature and is listed under the U.S. Endangered Species Act and the Mexican norm for threatened species (NOM-059-SEMARNAT-2010), which includes species considered at risk of extinction (Scientific Authority CITES Mexico 2001;DOF 2010;Valenzuela-Quiñonez et al. 2015). A recent increase in the illegal harvest of totoaba is a consequence of the near extinction of the yellow croaker or Chinese bahaba (Bahaba taipingenisis) in China (Sadovy & Cheung 2003). The dried swim bladders of totoabas and bahabas are similar in size and appearance and can garner prices from US$1,500 to US$20,000/kg dried on the black market in China (CITES 2016; Cisneros-Mata et al. 2020). ...
Article
The illegal harvest of marine species within exclusive economic zones can have a strong impact on the function of local ecosystems and livelihoods of coastal communities. The complexity of these problems is often overlooked in the development of solutions, leading to ineffective and sometimes harmful social and environmental outcomes. One-dimensional, oversimplified perspectives can lead to conservation prescriptions that exacerbate social stressors. This is particularly critical in the case of international illegal trade of endangered, high-value species, which generate a value chain in which artisanal fishers are the first operational and often the weakest link of an intricate web. We examined 2 illegal fisheries, totoaba (Totoaba macdonaldi) and sea cucumber (Isostichopus badionotus and Holothuria floridana), in Mexico. Although these are 2 separate and independent fisheries, important ecological (resource condition, fishery impacts at the ecosystem level) and social (governance, markets) similarities improve understanding of their complexity. Our findings are relevant globally and show the need for interdisciplinary decision-making groups, community engagement, and the development of demand reduction measures.
... For most fishes, their reproductive cycle is linked to seasonal events and social cues, so that reproduction occurs under optimal environmental conditions (Eddy and Handy, 2012). Spawning migrations and aggregations are highly variable both spatially and temporally, and can last from just a few hours, to daily or monthly, some following the lunar cycle, or triggered by temperature regimes or tidal patterns (Sadovy and Cheung, 2003). In a warming climate, spawning periods are likely to be triggered earlier and such changes should be assessed accordingly. ...
Article
Seasonal fishery closures, are an input control measure to reduce fishing pressure on spawning stocks in fisheries management. Despite the huge foregone economic losses from such closures, the efficacy of them has yet to be examined in Turkey. This study compares the monthly landed catch distribution for commercial marine species averaged for 12 years (2006-2017) from Istanbul fish market, to catch rates of those species during the spawning seasons. Our results revealed that at first glance, most commercially important fish species examined here have their spawning seasons protected under the Turkish industrial seasonal closure period, especially for small and medium pelagics, as well as some demersals. On the other hand, taxa with winter spawning seasons such as Merlangius merlangus, John dory Zeus faber, brown meagre Sciaena umbra, big-scale sand smelt Atherina boyeri, and bogue Boops boops do not benefit from the commercial fisheries summer closure (>50% of their catch total). Also, some species are still heavily fished (>35% of their catch total) during the closure implying they are mainly targeted by small-scale fisheries (SSF). To help rebuild the commercial fisheries, we recommend the accompaniment of the industrial closure with the use of 'Real Time Closures' (RTCs) applied to all fishing sectors for species highly fished during their spawning periods and spawning habitats.
... Chinese bahaba is one of the largest croakers, reaching two metres long [32]. Maws from Chinese bahaba are always very large and thick, i.e., different from samples S1 and S3 in this study. ...
Preprint
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Background: Fish maws (dried swim bladders of fish) have long been used as a medicinal material and valuable tonic food which are very popular in Southeast Asia. It is difficult to identify the original species of fish maws sold on the market due to a lack of taxonomic characteristics. The present study aims to investigate the origin of commercial fish maws using DNA sequencing based on a partial sequence of the mtDNA 16S rRNA gene. Methods: Mitochondrial genomic DNA was extracted from a total of 44 individual fish maw samples collected from different markets by a QIAamp® DNA Mini Kit. The fragments of the 16S rRNA gene were amplified by PCR and bidirectionally sequenced using an ABI 3730 genetic analyser. Sequence assembly was performed with DNASTAR SeqMan software, and the resulting sequence was compared with reference sequences in GenBank using BLAST. Interspecific divergence and intraspecific variation were calculated by the Kimura 2-parameter model. Sample sequences were clustered in MEGA 6 using a neighbour-joining tree. Results: Forty-two of 44 fish maw samples were sequenced successfully. Fourteen taxa matched known fish species in the DNA sequence database, and 10 of them were supported by high homogeneity (99-100%). According to the results, 88% of the total samples belonged to family Sciaenidae. The clustering and genetic distance results, including in-group divergence and out-group divergence, indicated confidence in species identifications. Moreover, there was no strict correspondence between the commercial names provided by traders and the origin of the fish maws. This study also found a probable correlation between the molecular characteristics and morphological features of fish maws from croakers and non-croakers. Conclusion: In this study, DNA sequencing based on mtDNA 16S rRNA was carried out successfully to identify the origin of ~95% of the samples. This result indicated that 16S rRNA is a suitable barcode for identifying fish maws. The identification results allowed us to learn more about the fish species available in the fish maw market in Guangdong-Hongkong-Macao Great Bay. In addition, the association between trade category and species found in this study provides both consumers and merchants with an important reference for identifying the origin of fish maws.
... Esto ha determinado la merma de las cosechas en los niveles tróficos inferiores (Pauly et ál., 1998;Allan et ál., 2005). Algunas especies caracterizadas por su alta actividad reproductiva y alta tasa de renovación pueden llegar a extinguirse (Sadovy y Cheung, 2003), y especies de niveles tróficos bajos y con elevadas biomasas muestran niveles de biomasa muy por debajo de los niveles históricos, lo que se traduce en una reducción de las capturas anuales (Da Rocha et ál., 2014). Asimismo, la pesca incidental y la degradación de los hábitats también suponen pérdidas de biodiversidad marina (Worm et ál., 2006(Worm et ál., , 2009Allan, 2005) y pueden repercutir en ciertos procesos ecológicos, como la depredación (Myers et ál., 2007), la bioerosión (Bellwood et ál., 2003), la provisión de alimento a las aves marinas (Jahncke et ál., 2004) y el transporte de los nutrientes (Allan et ál., 2005). ...
Chapter
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Resumen ejecutivo: La pesca y acuicultura son sectores de enorme interés en algunos de los países iberoamericanos. La región de Iberoamérica alberga ecosistemas únicos, diversos y productivos que aportan más del 10 % a la producción pesquera mundial y solo en América Latina y el Caribe dan ocupación a casi 2,4 millones de personas. Tanto la pesca como la acuicultura se ven sometidas a diversas amenazas. Las amenazas potenciales para la pesca y la acuicultura son: (i) cambios en temperatura del mar a nivel local; (ii) acidificación del océano; (iii) aumento en el nivel del mar; (iv) cambios en la concentración de oxígeno ambiental; (v) incremento en la severidad y frecuencia de las tormentas; (vi) cambios en los patrones de circulación de corrientes marinas; (vii) cambios en los patrones de lluvia; (viii) cambios en los caudales de ríos, y (ix) cambios en flujos biogeoquímicos (nitrógeno). La pesca y la acuicultura, en la mayoría de los países de la región, no han recibido la suficiente atención como otros sectores productivos. Esto es así a pesar de que ya se están observando los efectos del cambio climático en la productividad del sector. Las proyecciones realizadas muestran un panorama crítico para algunos países y un alto riesgo para las comunidades que dependen del sector. El Caribe es una de las regiones de Iberoamérica con mayor vulnerabilidad a las amenazas del cambio climático, incluido el incremento del nivel del mar. Actualmente ya se observan mortandades elevadas y blanqueo de los arrecifes de coral en la región, y las proyecciones para fin de siglo muestran un mayor aumento de la temperatura y la acidificación. En las aguas ibéricas atlánticas los cambios en la composición y distribución de las especies se están traduciendo en cambios importantes en las pesquerías y tendrán un efecto en las comunidades de pescadores y en los consumidores. La producción de mejillones presenta un alto riesgo frente a la reducción de la productividad, un incremento de los blooms de algas tóxicas y la acidificación. Las actuaciones de adaptación planificada para el sector de la pesca y acuicultura, especialmente en América Latina y el Caribe, son escasas y mayormente se registran acciones de adaptación autónoma. En los países de la RIOCC existe un amplio portafolio de políticas públicas sobre cambio climático tanto en adaptación como en mitigación. Sin embargo, pese a los esfuerzos de los gobiernos, todavía no se implementan de manera práctica en el sector pesca. La sobrepesca, la contaminación, la introducción de especies exóticas y el mal uso de los cuerpos acuáticos en la región, y en especial en América Latina, son factores de estrés no climáticos que agravan los impactos del cambio climático. Los esfuerzos de transformación en el sector de la pesca y la acuicultura deben ser orientados a incrementar la capacidad de adaptación de las comunidades más vulnerables (ya sea por falta de recursos, por género u otros factores) fortaleciendo la gobernanza, el desarrollo del conocimiento y reduciendo los niveles de pobreza e inseguridad alimentaria. Tanto en la pesca como en la acuicultura existen opciones para la adaptación. Las principales opciones de adaptación en el sector son: cultivo de especies con mayor tolerancia térmica, salina y a la hipoxia; formulación de nuevos alimentos; planes de manejo adaptativo y con enfoque ecosistémico, monitoreo espacial de los recursos y la biodiversidad marina; reducción del descarte y la pesca incidental; análisis de riesgos en los planes de gestión; adaptación de la infraestructura portuaria; sistema de seguros ante eventos climáticos extremos; fomento del consumo de especies de peces de bajo valor comercial; artes y aparejos de pesca amigables; protección de hábitats críticos o esenciales en manglares y estuarios; mejora de sistemas de gobernanza (comanejo), y diversificación de los medios de vida de la población implicada. Palabras clave: Pesca, Acuicultura, Cambio Climático, Iberoamérica.
... Spawning grounds of some sciaenid species in Chinese waters were associated with estuaries. For B. taipingensis, the spawning grounds were associated with the Yangtze River, the Min River and the Pearl River Estuaries (Sadovy and Cheung 2003). For L. crocea, the spawning grounds were also associated with the river mouths along the Chinese coast (Liu and Sadovy de Mitcheson 2008). ...
Article
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Johnius taiwanensis is a newly described species from the Family Sciaenidae (Perciformes). The species is commonly found in shallow coastal waters along both sides of the Taiwan Strait, on the west sides of Zhejiang, Fujian, Guangdong and Hong Kong and east side of Taiwan, and has been misidentified for decades. We studied the reproductive biology of J. taiwanensis from Fujian coastal waters, southern China, using gonadosomatic index (GSI) and gonad histology analyses. Monthly sampling from July 2016 to October 2017 was conducted and a total of 638 specimens were collected, ranging from 7.3 to 19.0 cm standard length (SL). Gonad histology suggested that the spawning activity of J. taiwanensis females and males lasted from April to October, and the peak spawning months for females was July to September. Mature females and males were 12.5 and 11.8 cm SL, respectively, while the estimated sizes at 50% maturity were 12.0 cm and 10.9 cm SL, respectively. Vitellogenic stage oocytes (O3) and post-ovulatory follicles (POF) or hydrated oocytes (HO) were observed, and POF and O3 in ovaries indicated that J. taiwanensis spawns multiple times each spawning season. HO or both HO and POF were observed in ovaries collected from one same location in May 2017 and August 2016.
... While the Cuban example is unusually well documented, the fate of Cuban Nassau grouper populations has been repeated throughout the range of the species. Once FSAs are discovered, they are fished intensively; many such aggregations have ultimately been fished to the point where fish cease to aggregate (31)(32)(33)(34). In a contemporary context, few of the known remaining FSAs host more than 1,000 individuals (2,5,35,36). ...
Article
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Many large-bodied marine fishes that form spawning aggregations, such as the Nassau grouper ( Epinephelus striatus ), have suffered regional overfishing due to exploitation during spawning. In response, marine resource managers in many locations have established marine protected areas or seasonal closures to recover these overfished stocks. The challenge in assessing management effectiveness lies largely in the development of accurate estimates to track stock size through time. For the past 15 y, the Cayman Islands government has taken a series of management actions aimed at recovering collapsed stocks of Nassau grouper. Importantly, the government also partnered with academic and nonprofit organizations to establish a research and monitoring program (Grouper Moon) aimed at documenting the impacts of conservation action. Here, we develop an integrated population model of 2 Cayman Nassau grouper stocks based on both diver-collected mark–resight observations and video censuses. Using both data types across multiple years, we fit parameters for a state–space model for population growth. We show that over the last 15 y the Nassau grouper population on Little Cayman has more than tripled in response to conservation efforts. Census data from Cayman Brac, while more sparse, show a similar pattern. These findings demonstrate that spatial and seasonal closures aimed at rebuilding aggregation-based fisheries can foster conservation success.
... The meagre is a species with a fast growth [8] and high fecundity [9]. Adults migrate for spawning to estuaries and other coastal areas [10] [11] [12] [13] [14]. ...
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The meagre is a species of marine fish that has the most potential for Moroccan and Mediterranean finfish culture production. However, several constraints still limit its production (cannibalism, larval survival low rate and size heterogeneity of hatchery produced juveniles). This study is an attempt to produce meagre fry without recourse to meta-nauplii of Artemia sp, in order to further simplify the protocol for larval rearing of this species. In this study, Artemia was substituted by micro-diets in larval feeding. We used two feeding treatments in this study, treatment T1 and treatment T2, were we are comparing their effects on survival and growth of meagre larvae. In the treatment T1 we are using rotifers, Artemia, and micro-diets in larval feeding protocol while in treatment T2, Artemia was substituted by micro-diets. The results demonstrated that the larval growth in both treatments did not varied significantly from 1 st until 12 th day post hatching (dph), and thereafter larval growth increased significantly in T1 (P < 0.007). Significant difference in survival rates were found at 20 dph between both treatments (P < 0,009), with 23% and 15% in T1 and T2 respectively. the results obtained during this study have shown the technical feasibility of producing meagre fry without using the Artemia metanauplii. However, further research is still needed to improve and optimize the results obtained in this study compared to the common larval rearing protocol.
... Understanding of the biodiversity impact of overfishing is compounded by its long history, the absence of systematic data collection for much of the world's coastal seas and oceans until recently, and the 'shifting baseline' psychology that means we are blind to changes prior to our human experience (Thurstan et al., 2015). As an example, overfishing is the main cause of decline and near extinction of iconic species including sawfishes (Everett et al., 2015;Dulvy et al., 2016), and the giant yellow croaker (Bahabia taipingensis; Sadovy and Cheung, 2003). These taxa depend on, and are highly catchable in, estuarine habitats (Figure 4). ...
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Despite the disparities in size and volume of marine and freshwater realms, a strikingly similar number of species is found in each – with 15 150 Actinopterygian fishes in fresh water and 14 740 in the marine realm. Their ecological and societal values are widely recognized yet many marine and freshwater fishes increasingly risk local, regional or global extinction. The prevailing threats in aquatic systems are habitat loss and degradation, invasive species, pollution, over-exploitation and climate change. Unpredictable synergies with climate change greatly complicate the impacts of other stressors that threaten many marine and freshwater fishes. Isolated and fragmented habitats typically present the most challenging environments for small, specialized freshwater and marine fishes, whereas overfishing is by far the greatest threat to larger marine and freshwater species. Species that migrate within or between freshwater and marine realms may face high catchability in predictable migration bottlenecks, and degradation of breeding habitat, feeding habitat or the intervening migration corridors. Conservation reserves are vital to protect species-rich habitats, important radiations, and threatened endemic species. Integration of processes that connect terrestrial, freshwater and marine protected areas promises more effective conservation outcomes than disconnected reserves. Diadromous species in particular require more attention in aquatic restoration and conservation planning across disparate government agencies. Human activities and stressors that increasingly threaten freshwater and marine fishes must be curbed to avoid a wave of extinctions. Freshwater recovery programmes range from plans for individual species to recovery of entire basin faunas. Reducing risks to threatened marine species in coastal habitats also requires conservation actions at multiple scales. Most of the world's larger economically important fisheries are relatively well-monitored and well-managed but there are urgent needs to curb fishing mortality and minimize catch of the most endangered species in both realms. Copyright
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Fish maw, or swim bladder, has long been used as food and medicine in Asia, particularly in southern China. Considering its history as luxury and nutritious seafood, surprisingly little information on volumes, values, source of maw or species composition involved in the trade is available. In 2015, Hong Kong, the global trade hub for maw, introduced a ‘maw’ commodity code enabling a first global look at its trade. This study finds that 3144–3882 t of dried fish maw was imported annually to Hong Kong from 2015 to 2018, coming from about 110 countries/territories, with a declared import value of 264–394 million USD. These volumes and values, similar to those of the better-known sea cucumber and shark fin trades, highlight the growing importance of maw. Prices can involve massive mark-ups, with investment speculation associated with the most valuable maw categories. Similar volumes to those imported are re-exported annually, mostly to Vietnam. By volume, 50% of maw came from Uganda, Brazil, Tanzania, India and Vietnam. Species composition was dominated by croakers (Sciaenidae), with Lates perch (Latidae), pufferfish (Tetraodontidae), various catfish (Siluriformes) and pike conger (Muraenesocidae) also traded, among other species. This lucrative trade has two components, high value maw and cheaper maw for regular consumption, and is expanding into new markets, such as shark fin substitution. There is loose association between trade category and species which can lead to confusion for consumers. Considering possible threats to biodiversity and evidence of illegal and secretive trade, management is called for to harness benefits and reduce risks.
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Understanding migration dynamics of fishes that aggregate-spawn is critical if spatio- temporal closures to fishing are expected to protect them. Concern over fishing of Chrysophrys auratus spawning aggregations in embayments near a west Australian city led to an annual four-month spatial fishing closure. However, the extent to which it protects fish migrating to and from aggregations is unclear. Acoustic telemetry demonstrated a bimodal pattern of entry to and departure from the main embayment via only one of several pathways. Among years, 33-56% of fish occurred in the pathway prior to the closure, but most left before it ceased. Fish were detected within the closure in multiple but not always consecutive years. Variation in migration timing and aggregation philopatry may alter capture risk, but pre-and post-spawning migratory fish are fished in the main pathway and adjacent reefs, which would presumably impact spawning aggregation biomass. Assessment of this would assist in understanding whether expansion of the closure's spatial and temporal limits is necessary to ensure spawning biomass or if current management is sufficient.
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The directed harvest and global trade in the gill plates of mantas, and other mobulid rays, has led to increased fishing pressure and steep population declines in some locations. The slow life history, particularly of the manta rays, is cited as a key reason why such species have little capacity to withstand directed fisheries. Here, we place their life history and demography in the context of other sharks and rays. Despite the limited availability of data, we use life history theory and comparative analysis to develop plausible ranges of somatic growth rate, annual pup production and age at maturity to estimate risk of extinction (maximum intrinsic rate of population increase rmax) using a variant of the classic Euler-Lotka model. Manta ray rmax is most sensitive to the length of the reproductive cycle, and the median rmax of 0.11 year-1(CI: 0.089-0.137) is one of the lowest known of the 106 sharks and rays for which we have comparable demographic information. In common with other unprotected, unmanaged, high-value large-bodied species with low or very low productivity, manta rays are unlikely to sustain unmonitored, unregulated exploitation and may face increasing local and regional extinction risk.
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Risk of impact of marine fishes to fishing and climate change (including ocean acidification) depend on the species’ ecological and biological characteristics, as well as their exposure to over‐exploitation and climate hazards. These human‐induced hazards should be considered concurrently in conservation risk assessment. In this study, we aim to examine the combined contributions of climate change and fishing to the risk of impacts of exploited fishes, and the scope for climate‐risk reduction from fisheries management. We combine fuzzy logic expert system with species distribution modeling to assess the extinction risks of climate and fishing impacts of 825 exploited marine fish species across the global ocean. We compare our calculated risk index with extinction risk of marine species assessed by the International Union for Conservation of Nature (IUCN). Our results show that 60% (499 species) of the assessed species are projected to experience very high risk from both overfishing and climate change under a “business‐as‐usual” scenario (RCP 8.5 with current status of fisheries) by 2050. The risk index is significantly and positively related to level of IUCN extinction risk (ordinal logistic regression, p < 0.0001). Furthermore, the regression model predicts species with very high risk index would have at least one in five (>20%) chance of having high extinction risk in the next few decades (equivalent to the IUCN categories of vulnerable, endangered or critically endangered). Areas with more at‐risk species to climate change are in tropical and subtropical oceans, while those that are at risk to fishing are distributed more broadly, with higher concentration of at‐risk species in North Atlantic and South Pacific Ocean. The number of species with high extinction risk would decrease by 63% under the sustainable fisheries‐low emission scenario relative to the “business‐as‐usual” scenario. This study highlights the substantial opportunities for climate‐risk reduction through effective fisheries management.
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Con il declino delle risorse alieutiche provenienti da acque costiere poco profonde, la crescente domanda e le nuove tecnologie, la pesca si sta espandendo, a livello globale, in acque sempre più profonde. Nel Mediterraneo tale espansione è motivata dall'alto valore commerciale dei gamberi di profondità Aristeus antennatus e Aristaeomorpha foliacea. Un eccessivo sforzo di pesca può comportare un pericolo per le specie appartenenti alle comunità batiali poiché, a causa dell’elevata longevità, crescita lenta, maturità tardiva e bassa fecondità, esse risultano più vulnerabili. Inoltre, anche i fattori ambientali rivestono un ruolo fondamentale nel modellare tali comunità. Il presente studio è stato rivolto a indagare i possibili effetti della pesca e di alcuni fattori ambientali sulle comunità dei fondi batiali del Mar Ligure e Alto-Medio Tirreno tramite analisi delle tre categorie faunistiche di maggior rilevanza (Crostacei, Condroitti e Osteitti) ivi presenti. Particolare attenzione è stata prestata alla ricerca delle possibili cause che determinano la segregazione tra Mar Ligure e Mar Tirreno, in termini di specie prevalente, nella distribuzione di A. foliacea e A. antennatus. I dati provenienti dalle campagne di pesca a strascico MEDITS (1994-2015), sono stati analizzati, attraverso modelli Additivi Generalizzati (GAM), al fine di stabilire una relazione tra biomassa ittica e fattori esterni. I risultati mostrano che la biomassa di Crostacei, Condroitti e Osteitti è significativamente correlata sia con fattori ambientali, che antropogenici. Anche la divisione geografica tra i due gamberi A. foliacea e A. antennatus sembra legata sia a fattori ambientali, che all'effetto della pesca. In particolare, A. antennatus è prevalente dove lo sforzo di pesca è maggiore (Mar Ligure). Questo è dovuto alla maggior resilienza di A. antennatus all'impatto della pesca.
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Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa.We have compiled 133 local, regional and global extinc-tions of marine populations. There is typically a 53-year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical compara-tive methods, which suggests that marine extinctions may have been underestimated because of low-detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insu¤ciently con-servative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large-scale dispersal characteristics. For commer-cially exploited species, it is often argued that economic extinction of exploited popula-tions will occur before biological extinction, but this is not the case for non-target species caught in multispecies ¢sheries or species with high commercial value, espe-cially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of ¢sh populations have been invoked to avoid listing commercial species of ¢shes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee e¡ect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence sug-gests that ¢sh populations do not £uctuate more than those of mammals, birds and but-ter£ies, and that ¢shes may exhibit vulnerability similar to mammals, birds and butter£ies. There is an urgent need for improved methods of detecting marine extinc-tions at various spatial scales, and for predicting the vulnerability of species.
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growth and late maturity Severe population declines have been documented for several snappers and groupers (Lutjanidae, Serranidae) in the Atlantic and the Gulf of California, several rockfishes (Sebastinae) in the Pacific, and some sharks (Selachei), skates (Rajidae), and sawfishes (Pristidae). Regulatory agencies should be apprised that these groups are extraordinarily vulnerable, and priority management should be given to these species, The greatest threat to many long-lived marine species may be bycatch (including regulatory dis- card) in fisheries,tar geting other, often more-productive species. Regulatory,agencies must monitor bycatch of long-lived species and move to implement conservation actions if population declines are recorded. The most effective management strategy for some species taken as bycatch and for tar- geted species such as deeper-water groupers and Pacific rockfishes, may be establishment of large, protected marine reserves to supplement traditional management practices outside of the protected areas. The AFS supports the development, use, and evaluation of large marine reserves or Marine Protected Areas to protect and rebuild vulnerable populations. These reserves must have clearly defined goals, include a wide variety of environmental conditions, be of sufficient number to pro- tect marine ecosystems within each region, allow adaptive management, and be large enough to be self-sustaining. The AFS encourages its members to become involved by providing technical infor- mation needed for protection of at-risk marine stocks to international , federal, state, and provincial policy makers, so decisions are made on a scientific, rather than emotional or political, basis.
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This initiative was supported by grants to AFS and the Virginia Institute of Marine Science by the Pew Charitable Trusts, NMFS Office of Protected Resources, National Fish and Wildlife Foundation, The Munson Foundation and the Homeland Foundation, J.A. Musick, Principal investigator.
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Quantitative criteria used to assign species to categories of extinction risk may,seriously overestimate these risks for marine,fishes. Contemporary,perception is that marine,fishes may,be less vulnerable to extinction than other taxa, because of great natural variability in abundance, high fecundity, rapid population growth, and an intrinsically high capability of recovering from low population size. Contrary to perception, however, there appears to be generally little theoretical or empirical support for the hypotheses,that marine,fish are more,likely to experience large reductions in population size, to produce unusually high levels of recruitment, to have higher reproductive rates, or to recover more,rapidly from,prolonged,population declines than nonmarine,fishes. Although existing population-decline criteria may not accurately reflect probabilities of biological extinction, they do appear to reflect the converse—population re - covery. Insufficient support for contemporary perceptions of their susceptibility to extinction, coupled with caveats as - sociated with the assignment of extinction risk, suggest that significant increases in the population-decline thresholds used to assign marine,fishes to at-risk categories would,be inconsistent with a precautionary approach,to fisheries man,- agement,and the conservation of marine,biodiversity. Résumé : Il est possible que les critères quantitatifs qui servent à placer les espèces de poissons marins dans les
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A change in attitude is urgently required to provide credibility to, and to devise methods for, combining and utilizing non-scientific information (local knowledge) together with more typical scientific data. In the midst of vast uncertainty about fish stocks, the climate is right for this change in attitude. Expert systems offer one tool to combine different sources of information in a meaningful way. We believe that through the simple communication required to gather knowledge for an expert system, the development of mutual respect will foster cooperation and responsibility of resource users, scientists and managers, thus providing the basis for improved and more responsible management.
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Jean Baptiste de Lamarck and Thomas Huxley, two of the foremost thinkers of the 18th and 19th centuries, believed that humanity could not cause the extinction of marine species. Their opinions reflected a widespread belief that the seas were an inexhaustible source of food and wealth of which people could barely use a fraction. Such views were given weight by the abundant fisheries of the time. Additionally, the incredible fecundity and wide distributions of marine fishes, combined with limited exploitation, provided ample justification for optimism. The ideas of Huxley and Lamarck persist to this day, despite a sea change in the scale and depth of our influence on the oceans. Marine species could be at a far greater risk of extinction than we have assumed.
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The dusky kob Argyrosomus japonicus is an important linefish species that is abundant in South African waters between Cape Agulhas and the Moçambique border. The juveniles (Y/R) and spawner biomass-per-recruit (SB/R) models were applied to the South African dusky kob stock, with accommodation for different inshore (Finshore) and offshore (Foffshore) fishing mortality. It is shown that, as a result of high juvenile mortality (Finshore = 4–6-fold FSB25 and 6–10-fold FSB40), dusky kob were exploited far beyond optimal (FSB40) and threshold (FSB25) fishing limits, and that SB/R was 1.0 – 4.5% of the pristine value. This is indicative of severe stock depletion and of recruitment overfishing. Based on the bag frequencies of 16 367 angler outings, it is clear that the current recreational bag limit of 10 fish·angler−1·day−1 does not limit fishing effort. Three alternative management scenarios (combinations of Finshore and minimum size at first capture) are discussed, which elevate SB/R above 25%SB/RF=0, increase Y/R beyond current levels, and equitably apportion Y/Rinshore and Y/Roffshore. Whereas it would take about 41 years for any of the alternative scenarios to attain maximum SB/R, a 3-fold increase is expected after 9 years and a 6.0 – 6.4-fold increase after 20 years. The increase in spawner biomass associated with the alternative strategies is expected to increase both inshore and offshore yield dramatically (as a result of higher recruitment), even though Y/Rinshore would be 69 – 70% of its current value. It is concluded that, because of the susceptibility of A. japonicus to recruitment overfishing, the species may have been overexploited in fisheries throughout its wide distributional range, and that accurate life history data and assessment-based regulations are essential for successful long-term management.
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The life history of Argyrosomus japonicus off the east coast of South Africa was studied using biological, size composition and tagging data from fish caught in the estuaries, surf zone and nearshore marine environment of three coastal regions. Capture methods included hook and line (all habitats), seine-netting (estuaries and surf zone), and gill-netting and trawling (estuaries only). Median total length (TL) at maturity was 920 mm (5 years) for males and 1 070 mm (6 years) for females. All males > 1 100 mm TL (7 years) and all females > 1 200 mm TL (8 years) were mature. Adult fish are found predominantly in the nearshore marine environment, but they also frequent estuaries and the surf zone. Spawning takes place in the nearshore environment, from August to November in KwaZulu/Natal, and from October to January in the Southern and South-Eastern Cape regions. A large proportion of the adult population migrates to KwaZulu/Natal to spawn, although spawning may continue on their return to the Cape. Early juveniles of 20–30 mm (∼4 weeks) are recruited into turbid estuaries along the entire East Coast. They remain in the upper regions of the estuaries until they grow to about 150 mm. Juveniles > 150 mm are found in estuaries and in the surf zone. Fish A. japonicus to evolve a life history with a large size at maturity, thereby "pre-adapting" it to a migratory life-style. The life history of A. japonicus, including late maturity, the use of estuarine and surf-zone nursery areas, and a migratory adult population which forms concentrated spawning aggregations, is particularly vulnerable to the activities of man.
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The genetic diversity of both wild and rearedpseudosciaena crocea (Richardson) collected from Guan-Jing-Yang in Ningde, China in May 1999 was investigated by random amplified polymorphic DNA (RAPD) in the present study. The polymorphism and mean difference of the wild population as revealed by RAPD were 18.9% and 0.0960 respectively, and those of the reared stocks were relatively lower, with 16.7% in polymorphism and 0.0747 in mean difference. The genetic distance between the two stocks was 0.0041. From the comprehensive investigation, the main reasons for the loss of genetic diversity were probably overfishing, small number of parents as broodstocks and the debatable artificial ranching. Results from this study also showed that the large yellow croaker populations distributed along Fujian coastal waters including Guan-Jing-yang still potentially wide genetic variability. It is suggested that genetic management and prevention should be scientifically conducted in order to maintain and improve the genetic diversity of theP. crocea population.
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The five principal food finfishes that made up more than 50% of the total catch of food finfishes in the Middle Atlantic region, from New York to Virginia, about 25 years ago were: Atlantic croaker (Micropogonias undulatus), weakfish (Cynoscion regalis), scup (Stenotomus chrysops), summer flounder (Paralichthys dentatus), and black sea bass (Centropristis striata). Of these, only black sea bass had not clearly declined in abundance up to that time. Subsequently, the Middle Atlantic region has shown the greatest proportional decline in landings and their total value of any coastal region of the United States, except for the Great Lakes. From 1929 to 1983, 16 different species ranked among the top five by weight. Whereas abundance of many species changed from natural causes, the major species also suffered from overfishing. In their place, new species of lesser value such as silver hake (Merluccius bilinearis) have been harvested more effectively. Even with these additional species the total catch of food finfishes has declined about 50% for the region since the peak in 1945. Pound nets and otter trawls have been the principal gears taking food finfishes in the Middle Atlantic region from 1908 to the present. Yet the percentage of the catch by each gear has changed drastically. Pound nets accounted for more than 50% of the catch from 1908 to 1939, but for only 7% in 1983. Otter trawls were infrequently used until the early 1930s; by the 1980s they were taking about 70% of all food finfishes. The present condition in the Middle Atlantic region suggests that further action is required by the Middle Atlantic Fishery Management Council and individual states to reverse the decline in the fisheries.
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We conducted a literature review on the biology, ecology, fishery, and protection of totoaba (Totoaba macdonaldi), an endemic, threatened fish of the Gulf of Calfornia, Mexico. Reinterpretation and integration of published and unpublished information enabled us to confirm and estimate specific biological parameters of the totooba, make hypothetical constructs of its life history, and to propose ideas for its preservation. In specific, we found (1) that the mean age of first reproduction of male and female totoaba are 6 and 7 years, respectively; (2) that the intrinsic rate of natural mortality was estimated as 0.268 per year and (3) that in the mid 1980s an estimated 120,300 juveniles died each year in the shrimp fishery by-catch and 6200 adults (26 kg average weight) died due to poaching. The parameters of an individual growth model for juveniles and adults were also estimated. Decreased spring water input from the Colorado River into the Gulf of California may have caused a contraction of the spawning season and a reduction of the carrying capacity of juvenile totoaba. An increase in annual survival during recent years indicates recovery of the stock that might be related to protection of adults. We argue that habitat restoration, which includes the elimination of growth and recruitment over-fishing, is critical to increasing numbers of totoaba, and thereby lifting the fishing ban, and to the delisting of totoaba.
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Conservation biologists and natural resource managers are both working to maintain species, but their approaches and priorities differ. The contrast was highlighted when the World Conservation Union (IUCN) listed some commercial fish species, such as the Atlantic cod (Gadus morhua), in the 1996 Red List of Threatened Animals. These species qualified under IUCN’s criteria because they had undergone a marked decline in abundance. Disagreements over these listings revealed fundamental differences between resource managers and conservation biologists. Resource managers aiming to maximize continuing yields using specific, explicit, and data-rich models, generally have not considered risk assessment and sometimes face the necessity for political compromises. Conservation biologists generally consider a wide diversity of species and operate in a data-poor and precautionary context with an overall aim of minimizing extinction risk. The IUCN Red List is an extreme case in point and uses simple criteria for evaluating the conservation status of all species. Under these circumstances, it can do little more than indicate a species’ status in order to prompt further investigation by the appropriate body. We suggest that productive collaboration between conservation biologists and resource managers will start with an understanding of these different perspectives and will benefit from common interests in precautionary approaches, ecosystem approaches, and adaptive management studies.
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Since the 1990s, artificial propagation and breeding technique of marine fish in China have developed by way of increasing species and fry numbers, with special stress laid on valuable species. Large quantities of artificial fry can meet the needs of both marine cage culture and pond culture for most species. Experimental results obtained by scientists have been put into use in actual production. Fish fry production has entered a period of sustainable development. So far, at least 44 species (21 families) of marine fish have been successfully bred in China. The artificial fry number of large yellow croaker (Pseudosciaena crocea) exceeded 300 million in 1999. The species whose artificial fry numbers have each surpassed 10 million annually are red drum (Sciaenops ocellatus), Japanese seabass (Lateolabrax japonicus), cuneate drum (Nibea miichthioides), spring spawning red seabream (Pagrosomus major) and threebanded sweetlip (Plectorhynchus cinctus). Millions of artificial fry are bred annually in the species of black porgy (Sparus macrocephalus), Russell's snapper (Lutjanus russelli), javelin grunt (Pomadasys hasta), miiuy croaker (Miichthys miiuy) and skewband grunt (Hapalogenys nitens). The fish in the family Sciaenidae are the main species in artificial propagation and breeding. Some problems and prospects on marine fish culture and stock enhancement are also discussed and some proposals for sustainable development are put forward in this article.
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For many of the worlds pelagic stocks, structure, dynamics and mesoscale distribution of fish shoals has considerable importance to central issues in fisheries management; stock structure, stock assessment, resilience and harvest control. A model is presented here, that attempts to bridge existing gaps in our basic understanding of the biological and ecological mechanisms underpinning the behavioural responses of herring, and how these govern spatial dynamics of shoals. The model, CLUPEX, is developed in the framework of an expert system and utilises fuzzy logic to capture and integrate scientific and local knowledge in the form of heuristic rules. Using input on biotic and abiotic environmental conditions, CLUPEX uses the rules to provide quantitative and qualitative predictions on the structure, dynamics and mesoscale distribution of shoals of migratory adult herring during different stages of their annual life cycle. Test predictions corresponded well with observed patterns, although accuracy for specific circumstances may be limited by the resolution of the knowledge. However, by adding specific local knowledge and adjusting weighting parameters, CLUPEX can be adapted to provide more accurate and precise predictions. The user interface combines hypertext and an explanation facility that is fully cross-referenced to a database, to provide an intuitive and transparent feel rarely found in more traditional analytical models.
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Managing most marine finfisheries to achieve optimum yields is an unattainable dream. Protecting these resources from serious depletion through precautionary management seems the only practical option. But even this is of limited application if we demand scientific data for each managed fishery. There are too few researchers to do the work and, in any event, such research would usually not be cost-effective. Thus, we need not merely precautionary management; we need data-less management.
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Are extinctions of marine vertebrates as rare and unlikely as current data indicate? Long-term research surveys on the continental shelf between the Grand Banks of Newfoundland and southern New England reveal that one of the largest skates in the northwest Atlantic, the barndoor skate (Raja laevis), is close to extinction. Forty-five years ago, research surveys on St. Pierre Bank (off southern Newfoundland) recorded barndoor skates in 10% of their tows; in the last 20 years, none has been caught, and this pattern of decline is similar throughout the range of the species.
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The coherent RAKE reception of wideband code division multiple access (W-CDMA) signals with complex spreading is considered. A general multipath-fading channel model is assumed. A dedicated pilot channel, which is separate from the data channels, is used for the purpose of channel estimation. Based on a digital implementation, the coherent demodulation scheme is presented. Pilot channel estimation error, due to multiple access and multipath interference, is studied. The system performance is evaluated by means of the bit error rate (BER). The analysis shows that the error of channel estimation significantly degrades system performance and can be effectively suppressed by low pass filters (LPFs). A discussion on the envelope variation of complex spread signals is also included, which illustrates that the complex spread signal has a more stable envelope than the dual-channel spread signal. The power ratio of pilot to data channels should be chosen in the range of 0.2 to 0.4 (or -7 to -4 dB), in order to achieve maximum system capacity
Fisheries Problems in theYellow and East China Seas
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in Taiping, on separate occasions, prices were: US$ 14 493 (RMB 120 000) per 50 kg ¢sh
  • Guangdong Taiping
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2000 Taiping, Guangdong Province, PRC In 2000 in Taiping, on separate occasions, prices were: US$ 14 493 (RMB 120 000) per 50 kg ¢sh (ˆ240 000 RMB and US$ 28 986 kg À1 of swimbladder);
PRC One ¢sh 1.5 m and 66.5 kg sold to Taiwan at US$ 24 155
  • Hong Kong Trader Talking To Mr Kwan Sai-Ping
Hong Kong trader talking to Mr Kwan Sai-ping, late 2000. 2001 Zhejiang, PRC One ¢sh 1.5 m and 66.5 kg sold to Taiwan at US$ 24 155 (RMB 200 000) ^ re£ecting the price of the swimbladder (newspaper article).