Visual censuses around drifting fish aggregating devices (FADs): a new approach for assessing the diversity of fish in open-ocean waters

Gaertner, Jean Claude; Taquet, Marc; Dagorn, Laurent; Mérigot, Bastien; Aumeeruddy, Riaz; Sancho, Gorka; Itano, David

doi:10.3354/meps07554

Cited by 16 publications

(21 citation statements)

References 39 publications

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“…These conclusions are similar to those of recent studies using the same multi-component approach, both for demersal fishes of the continental shelf in the Mediterranean Sea at regional [36], [40] and large scales [6], and also for pelagic fishes of the open sea in the Indian Ocean [54]. We found a high level of reproducibility of the number and the nature of the complementary diversity components evidenced for these different fish communities (demersal, pelagic), scales (local, regional, large), and habitats (coastal, open-ocean and now continental slope).…”

Section: Discussionsupporting

confidence: 91%

Large-Scale Diversity of Slope Fishes: Pattern Inconsistency between Multiple Diversity Indices

et al. 2013

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Large-scale studies focused on the diversity of continental slope ecosystems are still rare, usually restricted to a limited number of diversity indices and mainly based on the empirical comparison of heterogeneous local data sets. In contrast, we investigate large-scale fish diversity on the basis of multiple diversity indices and using 1454 standardized trawl hauls collected throughout the upper and middle slope of the whole northern Mediterranean Sea (36°3′- 45°7′ N; 5°3′W - 28°E). We have analyzed (1) the empirical relationships between a set of 11 diversity indices in order to assess their degree of complementarity/redundancy and (2) the consistency of spatial patterns exhibited by each of the complementary groups of indices. Regarding species richness, our results contrasted both the traditional view based on the hump-shaped theory for bathymetric pattern and the commonly-admitted hypothesis of a large-scale decreasing trend correlated with a similar gradient of primary production in the Mediterranean Sea. More generally, we found that the components of slope fish diversity we analyzed did not always show a consistent pattern of distribution according either to depth or to spatial areas, suggesting that they are not driven by the same factors. These results, which stress the need to extend the number of indices traditionally considered in diversity monitoring networks, could provide a basis for rethinking not only the methodological approach used in monitoring systems, but also the definition of priority zones for protection. Finally, our results call into question the feasibility of properly investigating large-scale diversity patterns using a widespread approach in ecology, which is based on the compilation of pre-existing heterogeneous and disparate data sets, in particular when focusing on indices that are very sensitive to sampling design standardization, such as species richness.

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Section: Discussionsupporting

confidence: 91%

Large-Scale Diversity of Slope Fishes: Pattern Inconsistency between Multiple Diversity Indices

et al. 2013

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“…In contrast, our multi-scale comparative analysis did not find the expected difference in patterns of variation in species diversity when the scale of observation varies (Wilsey et al 2005). It is also very similar to those observed for pelagic fishes (through underwater visual censuses around drifting fish aggregating devices) in the Indian Ocean (Gaertner et al 2008). when comparing Gulf of Lions and Iberian-Lions zone).…”

Section: Reproducibility Of the Multi-component Structure Of Groundfisupporting

confidence: 78%

“…Otherwise, the Berger-Parker index (1/d ), which is simple to understand and easy to measure (the identities of species other than the most abundant species do not need to be determined), might be a good candidate for summarizing the evenness component of diversity (Mérigot et al 2007a, Gaertner et al 2008. When a diversity component can be described by several redundant indices, we select the index that is the most intuitively simple to understand and easiest to calculate.…”

Section: Reproducibility Of the Multi-component Structure Of Groundfimentioning

confidence: 99%

Reproducibility of the multi‐component aspect of species diversity across different areas and scales: towards the constitution of a shortlist of complementary indices for monitoring fish diversity?

Gaertner¹,

Mérigot²,

Rélini³

et al. 2010

Ecography

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Recent theoretical and field studies conducted in both terrestrial and marine ecosystems have suggested that diversity could be a more complex and multi-component concept than previously thought. However, it is still poorly understood to what extent the information provided by the various indices is complementary with regard to diversity, and to what extent this complementarity is reproducible in different situations or at different scales of observation. In the present work, we have analysed the reproducibility of the empirical relationships between 11 diversity indices related to four major aspects (components) of species diversity (species richness, rarity, evenness and species taxonomy) in order to determine whether there is a general pattern of redundancy or complementarity in diversity measures that holds across years, areas and spatial scales. We have applied this approach to groundfish diversity through the analysis of 2404 trawl hauls collected during the first large-scale annual surveys carried out using a single sampling design throughout the northern Mediterranean Sea (ranging from 36.3 to 45.7°N, and 5.3°W to 28°E). Whatever the years, areas and scales studied, we found a strong reproducibility in the number and the nature of the main complementary components of diversity. The whole set of diversity indices considered may be roughly split into 6 complementary groups of descriptors. This result highlights that, in contrast to what is still the usual practice, monitoring diversity should not be based on only one or two of the most widely used components, even at large scale. Finally, in a context where developing tools for monitoring diversity is considered as a high priority worldwide, the strong reproducibility of the relationships between diversity indices we observed offers a basis for discussion of the feasibility and relevance of proposing a general shortlist of indices for monitoring diversity at different management scales

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“…However, some studies are not dedicated to a single area; some of them are comparisons between two areas or between different oceans. The similarity between the species lists from data obtained by visual censuses performed under anchored or drifting FADs in different oceanic regions, should encourage comparative studies between international oceans as this would make it possible to develop of specific indices in terms of pelagic diversity (Gaertner et al 2008). In an era of strong political commitments to implement large offshore Marine Protected Areas, it has become a priority to conduct research using FADs as observatory scientific tools.…”

Section: Literature Available On Fadsmentioning

confidence: 99%

Fish aggregating devices (FADs): good or bad fishing tools? A question of scale and knowledge

Taquet

2013

Aquat. Living Resour.

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-It is estimated that fish aggregating devices (FADs) are now used for over 40% of world tropical tuna catches, making this technique a major phenomenon for high seas fisheries worldwide, and one that has experienced great expansion over the past three decades. The question of whether the FAD is a good or a bad tool for the exploitation of marine resources depends on many parameters. To respond to this question, it is necessary to distinguish different scales of exploitation (artisanal vs. industrial) and various types of FADs (anchored vs. drifting), but it is also very important to gather more data and conduct further research on this topic to gain a better understanding of the phenomenon and of its impacts. As such, twelve years after the first international conference devoted to FADs, which was held in Martinique (French West Indies), a new multi-scalar global assessment of FAD fisheries development and a review of the progress of research in this field was deemed vital. The latest international conference, "Tuna Fisheries and Fish Aggregating Devices", was held in Tahiti in November 2011, and it was an event that welcomed nearly 150 conference attendees from 40 different countries, three ocean regions, and the Mediterranean. This is an analysis of the relevant literature gathered by the author in the bibliographic database FADBASE. Then, the major issues already addressed by the scientific community are set out, and gaps and research priorities are highlighted for anchored and drifting FADs management.

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Visual censuses around drifting fish aggregating devices (FADs): a new approach for assessing the diversity of fish in open-ocean waters

Cited by 16 publications

References 39 publications

Large-Scale Diversity of Slope Fishes: Pattern Inconsistency between Multiple Diversity Indices

Large-Scale Diversity of Slope Fishes: Pattern Inconsistency between Multiple Diversity Indices

Reproducibility of the multi‐component aspect of species diversity across different areas and scales: towards the constitution of a shortlist of complementary indices for monitoring fish diversity?

Fish aggregating devices (FADs): good or bad fishing tools? A question of scale and knowledge

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