Sound discrimination of two sympatric,threatened fish species allows for their in situ mapping

1. Human impacts on marine ecosystems are increasing and the number of fish species listed in the Red List is constantly growing. In the Mediterranean Sea, seven of the 10 bony fishes defined as Threatened by the IUCN are known to be vocal, including the target species of this study: the shi drum (Umbrina cirrosa Linnaeus, 1758) and the brown meagre (Sciaena umbra Linnaeus, 1758). As a result, non-invasive passive acoustic monitoring (PAM) can be used to pinpoint their distribution at sea. However, for PAM to be effective, reliable acoustic discrimination is required because the sounds they emit during reproduction are remarkably similar (i.e. short broadband pulsed sounds).
2. The shi drum and the brown meagre are closely related, elusive, vocal sciaenids, partially overlapping in their ecological niche. During summer 2019, three PAM surveys were conducted along the tidal inlets of the Venice lagoon (Italy). Here, the calls of both species have been recognized according to their temporal features: shi drum sounds were made up of a lower number of longer pulses with a different envelope, repeated at a lower rate than those of the brown meagre. Further, shi drum and brown meagre sounds of different origins (aquaculture and semi-natural conditions) were analysed and compared with those collected during the survey of the study area in order to validate the field collected data.
3. Call discrimination allowed for a fine-scale species mapping, showing a partially overlapping distribution of the two species along the inlets. This is the first case in which two sciaenids have been documented to share their reproductive habitat in the Mediterranean Sea.
4. This study demonstrates that it is feasible to acoustically monitor the target species even in those parts of the Mediterranean Sea where they co-exist. This, in its turn, could provide managers with the required data for effective conservation measures to be implemented.

     

Opportunities and challenges for analysis of wildlife trade using CITES data – seahorses as a case study

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Environmental flow releases trigger spawning of a threatened fish: Research insights and publication enhance management,credibility and relationships

1. Publication is an important stage in the research process, but determining the impact of published research on environmental outcomes is a complex challenge that is seldom undertaken. In 2016, a published study used acoustic telemetry techniques and drift sampling to demonstrate that environmental flow releases triggered downstream spawning migrations by a threatened fish species, the Australian grayling (Prototroctes maraena). The study provided support for the use of these types of releases to mitigate some of the effects of river regulation on fishes.
2. The impacts of this research and its publication in Aquatic Conservation: Marine and Freshwater Ecosystems were thoroughly reviewed to identify benefits to water managers, researchers, institutes, and the wider community.
3. Five areas in which this research, and its publication, had a recognizable impact are enhanced confidence for water managers in undertaking actions; greater acceptance in the wider community of environmental flow releases; enhanced relationships among water managers; the credibility arising from the work being published in a peer‐reviewed journal; and setting a foundation for further evidence‐based management.

     

Comprehensive estimates of seabird–fishery interactions for the US Northeast and mid‐Atlantic

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Salty stories,fresh spaces: Lessons for aquatic protected areas from marine and freshwater experiences

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Fishery benefits from behavioural modification of fishes in periodically harvested fisheries closures

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Bottlenose dolphins in the north-western Adriatic Sea: Abundance and management implications

1. The Adriatic Sea is one of the Mediterranean areas most heavily impacted by fishing and other human stressors. The northern part of the basin has been certified as an Important Marine Mammal Area because of the regular occurrence of common bottlenose dolphins, Tursiops truncatus.
2. Boat surveys, totalling 76 days at sea and 10,711 km of navigation, were conducted between April 2018 and October 2019 to assess cetacean abundance within a 3,000-km² area off Veneto, Italy. Bottlenose dolphins – the only marine mammal species observed – were encountered on 52 days and were tracked for 81 h and 26 min, resulting in 15,066 dorsal fin photographs of high quality and resolution.
3. Various capture–recapture models were applied on individual photo-identification datasets. Model-based estimates indicate that approximately 600 individuals occurred within the study area during the sampling period in both years. Abundance varied monthly: minimum estimates were obtained in May 2018 (291 individuals; 95% CI 134–630) and May 2019 (121; 95% CI 20–721), whereas maximum estimates were obtained in September 2018 (385; 95% CI 310–477) and October 2019 (494; 95% CI 378–645).
4. Evidence provided by this study can be used to complement and validate coarse ‘snapshot’ information from recent aerial surveys of the entire Adriatic Sea, and to enforce management action mandated by the European Community (EC) Habitats Directive and Marine Strategy Framework Directive, as well as guiding the EC’s Maritime Spatial Planning.

     

Alien turf: Overfishing,overgrazing and invader domination in south‐eastern Levant reef ecosystems

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Spatio-temporal distribution of mutton snapper and dog snapper spawning aggregations in the South-west Atlantic

1. Sites and periods of spawning aggregations of two important fishery resources, the mutton snapper, Lutjanus analis, and the dog snapper, Lutjanus jocu, were identified and validated along the Brazilian north-east coast (latitude 8–15°S) using exploratory analysis of catch per unit effort (CPUE) data, gonadosomatic index analysis, and gonad histology.
2. The CPUE analysis for both species allowed the identification of outliers and far outliers, representing fisheries with exceptional catches, which were used as proxies of possible aggregation.
3. The presence of pre-spawning and recent spawning signs (hydrated oocytes and post-ovulatory follicles) in the ovary of females caught at sites with recurrent records of high CPUE allowed the validation of spawning activity at those specific sites for each species. All aggregation sites identified in this study were located on the outer shelf, close to the shelf break, a region that has been declared an Ecologically and Biologically Significant Marine Area.
4. Comparison of two subregions showed significant differences in size structure of the fish sampled during landings, suggesting a fishing depletion effect in the north region.
5. For both species, reproduction peaked twice in all regions studied, with a more marked peak during summer. However, spawning activity was observed in almost every month of the year, suggesting that seasonal closures could be more effective if combined with spatial measures.
6. In the northern part of the study range, spawning grounds were found to lie just outside the boundaries of one of Brazil's largest marine protected areas. Inclusion of those grounds in the marine protected area would increase protection of these species and also mean increased protection of an Ecologically and Biologically Significant Marine Area, encompassing mesophotic reefs.
7. The identification of these spawning aggregations sites on the north-east coast of Brazil was conducted in collaboration with local fishers that traditionally use bottom handline. Co-management approaches are suggested in view of the importance of these fishing sites for traditional fishing communities that may also face threats due to encroachment of mobile fleets.

     

Age and growth of the Critically Endangered flapper skate,Dipturus intermedius

1. Knowledge of vital data such as growth and age at maturity is necessary to develop effective management strategies for endangered species. The Critically Endangered flapper skate (Dipturus intermedius) is the largest skate in the North Atlantic and growth information, necessary to assess key life-history traits, populations’ growth rates and anticipate their response to management measures, is still lacking.
2. While classical age estimation methods used in fish generally require the analysis of calcified structures, destructive methods are incompatible with conservation objectives for this species. Taking advantage of the high recreational value of the flapper skate, this study uses citizen-science data originating from photo-identification of trophy pictures and tag–recapture data supported by anglers to estimate growth in this Critically Endangered species. Using the growth increments measured between recapture events, an individual-based Von Bertalanffy growth model was fitted to the data using Bayesian inference.
3. The results confirm that the flapper skate is a long-lived species with ages estimated as >40 years for the largest individuals captured. Despite this longevity, the model reveals a relatively fast initial growth but relatively late ages at maturity and significant sex-related differences in both growth rate and maximum size.
4. These results suggest that population growth rate, and therefore recovery, might be much slower than previously reported. By using citizen science this study provides the necessary information to begin understanding population dynamics and monitor the recovery of an iconic Critically Endangered species.

     

Testing the exclusion capabilities and durability of the Sharksafe Barrier to determine its viability as an eco‐friendly alternative to current shark culling methodologies

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Size and age are important factors for marine sanctuaries: evidence from a decade of systematic sampling in a subtropical marine park

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Effects of a hook ring on catch and bycatch in a Mediterranean swordfish longline fishery: small addition with potentially large consequences

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岱衢洋产卵场鱼卵、仔稚鱼群落结构及其与环境因子的关系

为了解岱衢洋海域鱼卵、仔稚鱼的群落结构及其与环境因子的关系,本团队分别在2010年5月—2012年2月春、夏、秋和冬季,利用大型浮游生物网在此海域开展了8个航次调查。共采集到鱼卵1 042粒,仔稚鱼2 055尾,隶属于10目19科37种。鱼卵优势种为扁舵鲣和小带鱼等;仔稚鱼的优势种为鰉、鳀和中华小公鱼等。调查海域鱼卵的平均密度是8.40粒/100 m3,仔稚鱼的平均密度是14.85尾/100 m3。单因素方差分析结果显示,2010年和2011年春、夏季4个季节之间丰富度指数(D)、均匀度指数(J′)和多样性指数(H′)均存在极显著差异。鱼卵、仔稚鱼资源密度分布不均匀,春、夏季较高,冬季最低,大体呈现南高北低的趋势。Pearson相关性结果分析得出,与鱼卵、仔稚鱼关系最密切的环境因子为温度、盐度和海水悬浮物。研究表明,春、夏季是岱衢洋海域鱼类产卵的重要时期,该海域是鳀、扁舵鲣、中华小公鱼等中上层鱼类的重要产卵场和育幼场。     

Movement,depth distribution and survival of spinetail devilrays (Mobula japanica) tagged and released from purse‐seine catches in New Zealand

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Overcoming the constraints of low sample sizes to produce age and growth data for rare or threatened sharks

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Effectiveness of shore‐based remote camera monitoring for quantifying recreational fisher compliance in marine conservation areas

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A review of sawfishes (Pristidae) in the Arabian region: diversity,distribution, and functional extinction of large and historically abundant marine vertebrates

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Surveys of recreational anglers reveal knowledge gaps and positive attitudes towards manta ray conservation in Florida

1. South Florida has a significant number of recreational anglers, and some shore-based fishing sites overlap with habitat for juvenile manta rays. Although manta rays are prohibited from harvest in Florida, they are frequently seen foul-hooked or entangled in fishing line.
2. Recreational anglers (n = 198) were surveyed at piers and inlet jetties in Palm Beach County, Florida, USA to assess their knowledge of and actions and attitudes towards manta rays.
3. Analysis of the responses revealed that while most anglers could identify a manta ray (66.7%) and expressed no interest in casting at (93.4%) or catching a manta ray (95.5%), they lacked knowledge about threats to mantas, as well as their conservation and protected status. Surveyed anglers overwhelmingly supported manta ray conservation (82.3%) and environmental protection (98.0%).
4. Results indicate pier and inlet anglers are not using tackle strong enough to land a large ray to remove fishing gear, therefore it is recommended that outreach focuses on preventing recreational fishery interactions with manta rays, encouraging use of environmentally friendly tackle, and fostering engagement with anglers as citizen scientists.
5. These results can inform the design of outreach materials aimed at closing knowledge gaps and encouraging best practices. Positive attitudes towards the environment and existing neutral behaviours towards manta rays indicate an opportunity to shift the behaviour of shore-based anglers in this area in support of manta ray conservation.

     

Vulnerabilities and fisheries impacts: the uncertain future of manta and devil rays

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