Functional traits unravel temporal changes in fish biomass production on artificial reefs

Abstract

Artificial reefs (ARs) are deployed worldwide as they are expected to support fisheries management. While the underlying mechanisms remain widely debated, production was recently determined as the most probable cause of increases in fish biomass. Changes in fish biomass in a temperate AR system were investigated from December 2008 to November 2015 by considering seven distinct functional groups, and isotopic functional indices were used to identify how these changes may have affected organic matter (OM) fluxes. Contrasting patterns of change were observed between functional trophic groups, highlighting that combining the biomass of all species present in a community is inappropriate for assessing AR-induced effects. Benthic sedentary species predominated (>75% of the total biomass) through massive production, with a 68-fold increase in mean biomass over the study period. Mobile species tended to vary seasonally, suggesting only a slight influence of AR. Zooplanktivores biomass decreased over the 6-year period, as a possible result of changes in environmental conditions. Isotopic indices helped to reveal both the community maturation and the importance of local OM sources not only in supporting fish biomass production but also in attracting pelagic species. Our results corroborate that production and attraction are two extremes of a range of contrasting patterns and highlight the importance of considering the specific responses of functional components of fish communities to accurately describe changes in AR functioning. Functional attributes such as trophic traits, habitat use and dispersal abilities must not be overlooked as they modulate fish species responses to the deployment of man-made rocky substrates. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

Primary production and depth drive different trophic structure and functioning of fish assemblages in French marine ecosystems

“…the existence of a relationship between species, and may partly attest to the intensity of the flux, by calculating the relative importance of each source, but cannot directly estimate energy flows in the absence of information about the actual importance of each species in the ecosystem. As simultaneous collection of trophic and biomass or abundance data involves a good deal of work, most studies investigating the trophic structure of a fish community with stable isotopes classically do not include biomass data (but see Cresson et al, 2019;Duffill Telsnig et al, 2019;Trueman et al, 2014;Udy et al, 2019). As a result, patterns driven by species of low or high importance may be missed.…”

“…In addition, the vast majority of studies investigating the links between primary production and fish production and/or fisheries yields overlooked fish assemblage structure (e.g. Udy et al 2019;Ware and Thomson, 2005), despite the recent demonstration that including functional attributes (e.g separating benthic or pelagic piscivores) can be a powerful method to understand the links between primary production and fish biomass (Cresson et al, 2019;Petrik et al, 2019;Stock et al, 2017;van Denderen et al, 2018). The simultaneous collection of quantitative (i.e.…”

“…From the historical fisheries focus of the surveys, focus is put on fish assemblages and low trophic level groups may have appeared to be of minor interest, consistently with the expected risks of the addition of new data collection to existing surveys (de Boois, 2019). Several studies have demonstrated the importance of low trophic level consumers as drivers of trophic functioning in marine systems (Cresson et al, 2019(Cresson et al, , 2014bDay et al 2020;Garcia et al, 2011;Le Loc'h and Hily, 2005); including zooplankton and benthic invertebrates as actual components of the food web (and not just as isotopic references to study the fish community) seems to be a crucial future research avenue, as these groups may largely drive trophic fluxes in the communities.…”

Seasonal and plant-part isotopic and biochemical variation in Posidonia oceanica

“…1). The sampling site is located in the vicinity of an artificial reef system monitored since 2010 to understand in particular what organic matter fuels artificial reefs food webs (Cresson, Ruitton & Harmelin-Vivien 2014;Cresson et al, 2019), and how artificial reefs may alter the density and lower depth limit of the meadow (Astruch et al, 2015). In the laboratory, each shoot was separated among different leaf types depending on their age following the classification of Giraud (1979): juvenile (less than 5 cm long, with intact leaf tip), intermediate (more than 5 cm and without basal sheath) and adult (more than 5 cm, with a basal sheath).…”

Artificial reef design affects benthic secondary productivity and provision of functional habitat

“…Measures of secondary productivity indicate the energy flow through food webs and serve as a useful metric for comparing organisms and ecosystems that support different life histories and assemblages (Dolbeth et al, ). Previous research on artificial reef secondary productivity has largely focused on fish and has showed that in some cases artificial structures have the potential to support higher secondary productivity than natural reef habitats (Claisse et al, ; Cresson et al, ).…”