Use of local ecological knowledge,scientist's observations and grey literature to assess marine species at risk in a tropical eastern Pacific estuary

• 1. The loss of marine biodiversity in tropical regions of the world is a major threat to human welfare. Multiple anthropogenic drivers are responsible for this situation, with complex scenarios for coastal areas in third‐world countries, where economic development often competes with conservation plans.
• 2. The International Union for the Conservation of Nature (IUCN) Red List of Threatened Species is an influential tool for setting conservation priorities at local and regional levels. The application of IUCN criteria for assessing extinction risk, however, continues to represent a major challenge in data‐poor situations present in many tropical megadiverse countries.
• 3. To overcome these difficulties, three different data sources on invertebrates and fishes present in an estuarine system representative of the tropical eastern Pacific (TEP) region (Bahía Málaga, Colombia) have been used to establish their relative local extinction risk and correlate this information with the existing IUCN Red List categories. Data sources included (1) IUCN global and national listings, (2) traditional ecological knowledge (TEK), and (3) grey literature, scientific and natural history observations.
• 4. In total, 46 threatened species were evaluated after combining the three data sources. Only 17 species were previously identified as threatened by IUCN global and national listings, whereas the remaining 29 species were classified under a threatened category after evaluating TEK, grey literature and scientific information. Some of these species are seriously threatened within the estuary because of overharvesting and habitat destruction.
• 5. Despite most of the species identified having large geographical ranges in the TEP, they may face the same threats throughout their ranges. The approach provides a useful tool to assess species extinction risk in tropical regions where resource exploitation and habitat degradation advance rapidly, making the setting of conservation priorities an urgent task. Copyright © 2011 John Wiley & Sons, Ltd.

     

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

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

Integral Management Zones: A novel strategy for marine bivalve production in the Gulf of California,Mexico

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Fishery indicators during a predictable aggregation of Atlantic sharpnose sharks Rhizoprionodon terraenovae in the southern Gulf of Mexico: An alternative to assess a heterogeneous data‐poor fishery

Small‐scale fisheries in the southern Gulf of Mexico that catch Rhizoprionodon terraenovae (Richardson) are heterogeneous and data‐poor. Fishery‐dependent monitoring was conducted from 2010 to 2017, including a target season during an aggregation of this species to estimate data‐poor fishery indicators. During the target season, the average sizes for females and males (95.3 and 89.8 cm total length, respectively) were recorded, a global male sex bias (1:1.7), the highest percentage of mature sharks for all years (>89%), the highest values of CPUE (20.1 sharks/day) and size‐selectivity higher than the size at maturity. The spawning potential ratio was over 0.6 (reference point of 0.71) in the combined (target and non‐target) and target seasons for all years, which suggests that the fishery stock is not healthy. Annual assessment of this fishery can be carried out through monitoring during the target season, where management is more feasible to implement.     

Reconstructing 290 years of a data‐poor fishery through ethnographic and archival research: The East Pacific green turtle (Chelonia mydas) in Baja California,Mexico

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.     

Morphometry and histology to assess the maturity stage of three endangered devil ray species (Elasmobranchii: Mobulidae) from the Gulf of California

1. Devil rays of the genus Mobula are subject to fishing exploitation worldwide and are considered vulnerable to overexploitation due to population reduction, which is evidenced by a decline in the number of catches of these animals.
2. Limited biological knowledge on these species has forced the use of precautionary conservation measures in countries where intensive fishing occurs.
3. This study aimed to describe biological data of interest for estimating the feasibility of the recovery of Mobula populations, emphasizing the reproductive activity of three endangered species of the genus Mobula (Mobula munkiana, Mobula thurstoni, and Mobula mobular) in the Gulf of California.
4. Reproductive organs were collected during 7 years of commercial fishing (2001–2007), and data on population structure, sex ratio, gamete production, and the number of offspring per breeding period were obtained.
5. Maturity stages were determined through histological analysis of the gonads for both sexes, and the size at maturity was estimated based on anatomical and histological characteristics of the specimens caught.
6. Considering the wide global distribution of Mobula species, there is an urgent need to apply strict conservation measures, such as established fishery closures during the breeding season or the establishment of catch periods after specimens have reached sexual maturity, especially in the countries where these animals are caught.

     

Inland fisheries of the Mayan Zone in Quintana Roo, Mexico: Using a combined approach to fishery assessment for data-sparse fisheries

In Southern Mexico and Central America, inland fisheries form part of the livelihood portfolio of an as-yet unknown number of rural communities. This paper reports on the first comprehensive study of such fisheries located in common property lands (ejidos) of the Mayan Zone in Quintana Roo, Mexico. Given the “data-sparse” nature of these fisheries, with a lack of data available on their current status and on participation levels, a fishery assessment approach was used which included methods from both the natural and social sciences, with a focus on survey methods applied to fishery users, water, fish and creel surveys. Moreover, local knowledge of community residents complemented scientific knowledge in a substantial part of the research. The results, from 48 fishing sites (four with sub-saline waters, the remainder freshwater) indicated (1) a resource base of multi-specific nature with a total of 18 bony fish species in the study area, (2) artisanal (small-scale) fisheries, with very basic technology (notably hand-lines) utilized primarily through barefoot fishing along the shores, or with the aid of rafts and canoes, (3) seasonal fishing, primarily during the dry season (February to May), due to greater accessibility of the sites in those periods, but also related to the end of work on major local livelihoods, (4) both indigenous (Mayan) and non-indigenous fishers, of ages ranging from teenage to senior adults, for most of whom the major occupation was slash-and-burn agriculture, and (5) a mainly male-oriented fishery, but with some women involved in five out of nine ejidos studied. While the key motivation of fishers was subsistence, the study found, for the first time in this form of fishery, that recreation was also a significant goal of many participants. In terms of methodology, the study demonstrated the importance of cross-validating the accuracy of information from informants interviewed in the type of social surveys used here. This combined assessment approach proved effective in providing new information on these previously under-studied fisheries, and may be useful in similar data-sparse situations elsewhere.     

基于长度贝叶斯生物量法估算北部湾二长棘鲷种群参数

渔业数据缺乏是渔业资源评估和管理面临的难题。以2006—2018年北部湾二长棘鲷体长频率数据为例,运用基于长度频率的贝叶斯生物量方法 (LBB),估算二长棘鲷的渐近体长(L_∞)、最适开捕体长(L_copt)、相对自然死亡率(M/k)和相对捕捞死亡率(F/k)等种群参数。结果发现,2006—2018年间北部湾二长棘鲷的渐近体长平均为21.0 cm,最适开捕体长平均为12.6 cm,相对死亡率M/k、F/k、Z/k和开发率E分别为1.49、3.65、5.15和0.67。二长棘鲷的开捕体长和渐近体长的变化趋势一致,均呈下降趋势,且其生长速度有加快趋势。基于LBB估算的最适开捕体长和开发率与运用独立评估模型估算的结果基本一致。如果长度频率能代表资源开发阶段的长度组成,使用LBB估算的结果将较好地反映其真实情况。基于LBB的研究方法可为渔业数据缺乏情况下进行渔业资源评估提供借鉴。     

Dolphins in a bottle: abundance,residency patterns and conservation of bottlenose dolphins Tursiops truncatus in the semi‐closed eutrophic Amvrakikos Gulf,Greece

• 1. Boat surveys were conducted between 2002 and 2005 to study bottlenose dolphins living in the 400 km² Amvrakikos Gulf, western Greece. During 116 survey days, 4705 km of total effort resulted in the individual photo‐identification of 106 animals, through long‐term natural markings on their dorsal fins.
• 2. Mark–recapture analyses based on the M_th model provided estimates of 82 marked individuals in 2003 (95% CI=80–91), 92 in 2004 (95% CI=86–108) and 98 in 2005 (95% CI=94–110). To include the unmarked portion of the population, the proportion of unmarked individuals was computed based on the number of photographs of marked and unmarked dorsal fins. The mean proportion of unmarked animals in the population was 0.338 (95% CI=0.288–0.389). By adding this to the estimate for marked animals in 2005, considered as the most robust, a total population estimate of 148 individuals (95% CI=132–180) was obtained.
• 3. Dolphin encounter rates in 2003–2005 did not show significant variations, and averaged 7.2 groups per 100 km or 72.5 individuals per 100 km. Encounter rates within the Gulf were about one order of magnitude greater than those found for bottlenose dolphins in nearby eastern Ionian Sea coastal waters.
• 4. Mean dolphin density in the Gulf was 0.37 animals km^?2. This relatively high density, together with high levels of site fidelity shown by most individuals, was thought to be related primarily to prey availability, particularly of epipelagic schooling fish.
• 5. The importance of the semi‐closed Amvrakikos Gulf for bottlenose dolphins and other threatened species encourages the adoption of measures aimed to conserve its valuable ecosystems and raise the naturalistic profile of the area, while promoting environment‐conscious development. Meaningful action includes restoring natural hydrology (e.g. freshwater input from rivers), curtailing pollution from various sources, responsible fisheries and aquaculture management, and control of illegal fishing. Interactions between dolphins and fisheries also deserve careful quantitative investigation.

Copyright © 2007 John Wiley & Sons, Ltd.     

Using a topological approach to identify keystone species of fish in eutrophic lake ecosystems: A case of Zhushan Bay,Taihu Lake

Eutrophication is a global aquatic environmental problem. Traditional biomanipulation targeting keystone species has been effective for restoring eutrophic lakes. In this study, we conducted monthly fishery assessments and identified keystone species in Zhushan Bay of Taihu Lake, the most representative lake in the middle and lower reaches of the Yangtze River. We built the topological structure of Zhushan Bay's food web based on feeding relationships and calculated network indices of fish groups in the food web using network analysis, combined with Key Player Problem operation. Culter mongolicus, Culter alburnus, Protosalanx hyalocranius and Salangichthys tangkahkeii were the keystone species in Zhushan Bay's food web. Culter mongolicus and Culter alburnus had the greatest impact on the food web after removal. Protosalanx hyalocranius had the fastest speed of transmitting information. Salangichthys tangkahkeii was the key baitfish with the strongest ability to determine structure of species in higher trophic levels. Our study provided a reference for scientific management of shallow lake ecosystems and biological solutions for restoration of eutrophic lakes.     

Using biodiversity to valorise local food products: the case of fish ponds in a cultural landscape, their biodiversity, and carp production

Today, we need to produce sufficient food and simultaneously conserve biodiversity. But, could biodiversity associated with certain food production practices also be used in marketing products? We analyse this possibility for creating a food quality label for carp raised in the Dombes territory, a cultural landscape of fish ponds in France. The biodiversity of 99 fish ponds was studied in the Dombes territory by analysing aquatic vegetation, dragonflies, amphibians, macroinvertebrates, habitats around ponds, and water quality. In addition, a survey with 200 questionnaires and interviews was conducted with consumers to investigate fish and carp consumption and knowledge about quality labels and biodiversity. Findings reveal that fish production practices conserve remarkable species diversity, particularly for aquatic vegetation, dragonflies and amphibians, and habitats around the ponds. This relatively high level of biodiversity is found in spite of having very nutrient-rich fish pond systems, systems for which normally a low level of biodiversity is expected. Nevertheless, currently this biodiversity cannot be valorised for setting up a quality label for locally produced carp. Firstly, few consumers have adequate knowledge about carp and are interested in eating it. Secondly, most of them have less knowledge about the quality label which wanted to be established for carp from the Dombes. Thirdly, only less than one-third of the consumer is familiar with the term “biodiversity”. Fourthly, the stakeholder network of the supply chain is presently not able to communicate the message of biodiversity as they themselves lack a sufficient knowledge about biodiversity of their systems.     

Using occupancy and species distribution models to assess the conservation status and habitat use of the goldline darter (Percina aurolineata) in Georgia,USA

The goldline darter (Percina aurolineata) is threatened by recent increases in urbanisation in the Coosawattee River watershed, but no studies have addressed their current status. Similarly, limited data on habitat use make it difficult to understand factors that may impact this species. We compared occurrence data before (1996–2000) and after (2009–2011) a period of rapid development and population growth within the watershed. Single‐season occupancy models were built to account for imperfect species detection and to identify habitat covariates. MaxEnt was used to identify important stream reaches for conservation and to understand landscape scale factors correlated with the distribution of goldline darters. Our results indicate a high proportion of sites occupied upstream of Carters Lake during the historic and recent time periods, with no evidence of decline. However, occurrences of goldline darters for sites in Talking Rock Creek and the lower Coosawattee River were sparse in the historic period and absent during the recent period. The probability of detecting goldline darters is low and was positively associated with the occurrence of small substrate. Species distribution models were strongly influenced by watershed area and elevation and indicated a high probability of suitable habitat within the Coosawattee River and large tributaries upstream of Carters Lake. While goldline darter occupancy is currently stable upstream of Carters Lake, continued urbanisation is a threat to long‐term persistence. We recommend additional monitoring and describe a protocol that allows for precise estimates of species occupancy while minimising the risk of sampling‐related mortality.     

Comparing GLM,GLMM, and GEE modeling approaches for catch rates of bycatch species: A case study of blue shark fisheries in the South Atlantic

Modeling and understanding the catch rate dynamics of marine species is extremely important for fisheries management and conservation. For oceanic highly migratory species in particular, usually only fishery‐dependent data are available which have limitations in the assumption of independence and if often zero‐inflated and/or overdispersed. We tested different modeling approaches applied to the case study of blue shark in the South Atlantic, by using generalized linear models (GLMs), generalized linear mixed models (GLMMs), and generalized estimating equations (GEEs), as well as different error distributions to deal with the presence of zeros in the data. We used fractional polynomials to deal with non‐linearity in some of the explanatory variables. Operational (set level) data collected by onboard fishery observers, covering 762 longline sets (1,014,527 hooks) over a 9‐year period (2008–2016), were used. One of the most important variables affecting catch rates is leader material, with increasing catches when wire leaders are used. Spatial and seasonal variables are also important, with higher catch rates expected toward temperate southern waters and eastern longitudes, particularly between July and September. Environmental variables, especially SST, also affect catches. There were no major differences in the parameters estimated with GLMs, GLMMs, or GEEs; however, the use of GLMMs or GEEs should be more appropriate due to fishery dependence in the data. Comparing those two approaches, GLMMs seem to perform better in terms of goodness‐of‐fit and model validation.     

Co‐Infection with Pseudomonas anguilliseptica and Delftia acidovorans in the European eel,Anguilla anguilla (L.): a case history of an illegally trafficked protected species

Inspections by customs agents at Barcelona airport discovered 420 kg of contraband glass eels prepared for shipment to Hong Kong. After confiscation of these animals by police, they were transported to holding facilities to be maintained until after a judicial hearing. Upon arrival, they were separated into two groups and held under ambient flow‐through conditions in fresh water. During their captivity period, several peaks in mortality occurred and multiple bacterial strains were isolated from moribund animals. Sequencing of 16S rDNA was used to determine specific identity of the isolates. An initial isolation of Pseudomonas anguilliseptica was treated with oxytetracycline. A subsequent isolation of Delftia acidovorans proved resistant to oxytetracycline and was treated with gentamicin in combination with sulphadiazine–trimethoprim. Once the health condition of the animals was stabilized, they were partitioned into groups and subsequently released as part of a restocking effort for the species following the guidelines of Regulation (EC) 1100/2007 (Anon 2007). This represents the first record for both bacterial species in the host Anguilla anguilla in the Spanish Mediterranean.