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Extensive use of Fish Aggregating Devices together with environmental change influenced the spatial distribution of a tropical affinity fish.

ABSTRACT: Since the early 1990s of last century the spread of Caranx crysos a thermophilic fish species in the Mediterranean Sea has increased due to sea warming. Simultaneously, a large and unregulated use of fish aggregating devices has been recorded, and these devices seem to influence fish spatial distributions. Here we used a multidisciplinary approach to investigate the influence of environmental change and FAD presence on the spatial distribution of the tropical affinity fish species Caranx crysos across the Mediterranean Sea. Data suggested that the presence of C. crysos has increased progressively since 1990 towards the northwest side of the Mediterranean Sea, with the greatest number of recent findings occurring in zones with higher densities of FADs. The spatial distribution models show how the extensive use of FADs in combination with changes in environmental conditions may have indirectly facilitated the spread of the thermophillic C. crysos population across the Mediterranean Sea.

SUBMITTER: Sinopoli M

PROVIDER: S-EPMC6426954 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Extensive use of Fish Aggregating Devices together with environmental change influenced the spatial distribution of a tropical affinity fish.

Sinopoli Mauro M Lauria Valentina V Garofalo Germana G Maggio Teresa T Cillari Tiziana T

Scientific reports 20190320 1

Since the early 1990s of last century the spread of Caranx crysos a thermophilic fish species in the Mediterranean Sea has increased due to sea warming. Simultaneously, a large and unregulated use of fish aggregating devices has been recorded, and these devices seem to influence fish spatial distributions. Here we used a multidisciplinary approach to investigate the influence of environmental change and FAD presence on the spatial distribution of the tropical affinity fish species Caranx crysos ...[more]

PMID: 30894639

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Project description:BackgroundAggregation sites represent important sources of environmental heterogeneity and can modify the movement behavior of animals. When these sites are artificially established through anthropogenic actions, the consequent alterations to animal movements may impact their ecology with potential implications for their fitness. Floating objects represent important sources of habitat heterogeneity for tropical tunas, beneath which these species naturally aggregate in large numbers. Man-made floating objects, called Fish Aggregating Devices (FAD), are used by fishers on a massive scale to facilitate fishing operations. In addition to the direct impacts that fishing with FADs has on tuna populations, assessing the effects of increasing the numbers of FADs on the ecology of tuna is key for generating sound management and conservation measures.MethodsThis study investigates the effects of increasing numbers of FADs (aggregation sites) on the movements of tunas, through the comparison of electronic tagging data recorded from 146 individuals tunas (yellowfin tuna, Thunnus albacares, and skipjack tuna, Katsuwonus pelamis) tagged in three instrumented anchored FAD arrays (Mauritius, Oahu-Hawaii and Maldives), that differed according to their distances among neighboring FADs. The effect of increasing inter-FAD distances is studied considering a set of indices (residence times at FADs and absence (travel) times between two visits at FADs) and their trends.ResultsWhen inter-FAD distances decrease, tuna visit more FADs (higher connectivity between FADs), spend less time travelling between FADs and more time associated with them. The trends observed for the absence (travel) times appear to be compatible with a random-search component in the movement behaviour of tunas. Conversely, FAD residence times showed opposite trends, which could be a result of social behavior and/or prey availability.ConclusionOur results provide the first evidence of changes in tuna associative behavior for increasing FAD densities. More generally, they highlight the need for comparing animal movements in heterogeneous habitats in order to improve understanding of the impacts of anthropogenic habitat modifications on the ecology of wild animals.

Project description:Timor-Leste is one of the world's most malnourished nations where micronutrient-deficient diets are a contributing factor to the prevalence of child stunting, currently estimated to be 45.6% of children under five. Fish are an important source of nutrients and one that may assist the country's predominantly rural population of agriculturalists to exit poverty and malnutrition. However, a small national fishing fleet producing low catch volumes places fish out of reach of most inland and upland populations where it is needed most. Fish consumption is very low in rural, inland areas compared to coastal, regional, and global averages. This study is a one-year, partially masked, cluster-randomized controlled trial among families living in rural, inland Timor-Leste. We aim to test and compare the effects of two treatments, alone and in combination, on the frequency and volume of household fish consumption in rural, inland areas as a proxy for improved dietary diversity and micronutrient intake. Treatment 1 is the installation of nearshore, moored fish aggregating devices (FADs) to improve catch rates with existing fishing gears. Treatment 2 is a social and behaviour change (SBC) activity to promote fish consumption. Villages in inland communities will be randomized to receive treatment 1, treatment 2, both treatments, or neither treatment. Data will be collected at baseline (prior to the rollout of the treatments) and endline. Our study will determine the impact of an improved supply of fish, along with nutrition-oriented SBC activities, on the fish purchasing and consumption practices of rural, inland households. Findings from this study are urgently needed by Small Island Developing States to guide policy and investment decisions on how best to improve households' diets using locally available, nutrient-dense foods such as fish. Investments such as these are needed to break the cycle of malnutrition. This trial is registered at clinicaltrials.gov (NCT04729829). Trial registration: Trial registered at clinicaltrials.gov Identifier: NCT04729829.

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Extensive use of Fish Aggregating Devices together with environmental change influenced the spatial distribution of a tropical affinity fish.

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Extensive use of Fish Aggregating Devices together with environmental change influenced the spatial distribution of a tropical affinity fish.

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