The importance of targeted spawning aggregation fishing to the management of Seychelles’ trap fishery

Robinson, Jan; Samoilys, Melita; Grandcourt, Edwin; Julie, Danny; Cedras, Maria; Gerry, Calvin

doi:10.1016/j.fishres.2011.08.015

Cited by 22 publications

(25 citation statements)

References 25 publications

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“…As functional redundancy is limited, even if the majority of browsing fish species remain, loss of the crucial large entire thallus-feeders might render leaf-feeders alone incapable of removing sufficient algal biomass, jeopardizing successful returns to coral dominance after macroalgal phase-shifts, and ultimately compromising reef resilience (see Nash et al 2015). Indeed, this scenario appears to be unfolding in the Seychelles, where a system in which siganids are one of the dominant herbivores (Robinson et al 2011;Chong-Seng et al 2014) is revealing a limited capacity to reverse macroalgal phase-shifts ); a response that may have arisen as a result of overfishing large entire thallus-eating algal browsers ).…”

Section: Discussionmentioning

confidence: 99%

Feeding characteristics reveal functional distinctions among browsing herbivorous fishes on coral reefs

2015

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The removal of macroalgal biomass by fishes is a key process on coral reefs. Numerous studies have identified the fish species responsible for removing mature macroalgae, and have identified how this varies spatially, temporally, and among different algal types. None, however, have considered the behavioural and morphological traits of the browsing fishes and how this may influence the removal of macroalgal material. Using video observations of fish feeding on the brown macroalga Sargassum polycystum, we quantified the feeding behaviour and morphology of the four dominant browsing species on the Great Barrier Reef (Kyphosus vaigiensis, Naso unicornis, Siganus canaliculatus, and Siganus doliatus). The greatest distinction between species was the algal material they targeted. K. vaigiensis and N. unicornis bit on the entire macroalgal thallus in approximately 90 % of bites. In contrast, Si. canaliculatus and Si. doliatus avoided biting the stalks, with 80-98 % of bites being on the macroalgal leaves only. This distinctive grouping into 'entire thallusbiters' versus 'leaf-biters' was not supported by size-standardized measures of biting morphology. Rather, speciesspecific adult body sizes, tooth shape, and feeding behaviour appear to underpin this functional distinction, with adults of the two larger fish species (N. unicornis and K. vaigiensis) eating the entire macroalgal thallus, while the two smaller species (Si. canaliculatus and Si. doliatus) bite only leaves. These findings caution against assumed homogeneity within this, and potentially other, functional groups on coral reefs. As functional redundancy within the macroalgal browsers is limited, the smaller 'leaf-biting' species are unlikely to be able to compensate functionally for the loss of larger 'entire thallus-biting' species.

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Section: Discussionmentioning

confidence: 99%

Feeding characteristics reveal functional distinctions among browsing herbivorous fishes on coral reefs

2015

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“…Our study is one of the first to provide approximations of movement and home range size of the commercially important S. sutor , and subsequently strengthens our knowledge of their role as mobile herbivorous trophic links on coral reefs. Previous observations on the behaviour of this species confirm that they travel in big schools (Randall et al ., ; Robinson et al ., , ), and so the home ranges displayed by the tagged individuals expectedly represent a significant proportion of the population.…”

Section: Discussionmentioning

confidence: 99%

“…In the small island nation of the Seychelles, rabbitfishes are the main target species (~60% by weight) of the artisanal fishery catch (Grandcourt & Cesar, 2003;Robinson et al, 2011), with S. sutor being the most sought-after species (Grandcourt & Cesar, 2003;Seychelles Fishing Authority, 2016). The local authorities have established minimum mesh size requirements for fish traps used (i.e., 40 mm), but these restrictions are poorly regulated (Robinson et al, 2011), so juvenile fish are often captured and landed illegally (Grandcourt & Cesar, 2003). This species frequents coral reefs and feeds on seagrass (Ebrahim et al, in press), and so there is an assumption that they may be acting as mobile links between these habitats.…”

Section: Introductionmentioning

confidence: 99%

The commercially important shoemaker spinefoot, Siganus sutor, connects coral reefs to neighbouring seagrass meadows

Ebrahim

Bijoux

Mumby

et al. 2020

Journal of Fish Biology

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Spatial management of fish populations can potentially be optimized by determining the area of influence of a particular species. We performed an acoustic tagging study implemented on Denis Island in the Seychelles to assess the area of influence of the heavily targeted shoemaker spinefoot, Siganus sutor. We investigated whether this species acts as a mobile link between coral patches and seagrass meadows, and whether their movements differed between day and night. The study incorporated an array of 22 acoustic stations deployed within dense coral patches, seagrass meadows and mixed habitats of both seagrass and coral. Fifteen S. sutor carrying internal acoustic tags were monitored from November 2016 until May 2017. Detection patterns revealed them to be diurnal herbivores, with only rare nocturnal movements. Home‐range estimates showed that individuals differed in their spatial range extents and habitats used, covering ~15% of the total shallow subtidal coastline of the island. However, they displayed very small daily movements (<200 m), concentrated mainly around sites within mixed coral and seagrass habitats. An optimal number of detections was recorded when the coral to seagrass area ratio was approximately 1.6:1. This ratio was confirmed through statistical prediction modelling. Identification of such links of commercially important species between networked habitats may help authorities consider incorporating seagrass meadows of the Seychelles into management discussions, which are currently lacking.

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“…Spawning of these species commonly takes place at well-defined sites (Claydon et al, 2014), and migration from/to spawning sites could be a possible reason for the differing abundances of these species during neap tides. Due to their predictability in time and space spawning migrations also have direct consequences for fish catchability (Bos and Gumanao, 2012) and hence for conservation and management strategies of exploited stocks (Robinson et al, 2011).…”

Section: Lunar Cyclementioning

confidence: 99%

Lunar, diel, and tidal changes in fish assemblages in an East African marine reserve

Kruse

Taylor

Muhando³

et al. 2016

Regional Studies in Marine Science

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The importance of targeted spawning aggregation fishing to the management of Seychelles’ trap fishery

Cited by 22 publications

References 25 publications

Feeding characteristics reveal functional distinctions among browsing herbivorous fishes on coral reefs

Feeding characteristics reveal functional distinctions among browsing herbivorous fishes on coral reefs

The commercially important shoemaker spinefoot, Siganus sutor, connects coral reefs to neighbouring seagrass meadows

Lunar, diel, and tidal changes in fish assemblages in an East African marine reserve

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