Fish attraction to artificial reefs not always harmful: a simulation study

Abstract

The debate on whether artificial reefs produce new fish or simply attract existing fish biomass continues due to the difficulty in distinguishing these processes, and there remains considerable doubt as to whether artificial reefs are a harmful form of habitat modification. The harm typically associated with attraction is that fish will be easier to harvest due to the existing biomass aggregating at a newly deployed reef. This outcome of fish attraction has not progressed past an anecdotal form, however, and is always perceived as a harmful process. We present a numerical model that simulates the effect that a redistributed fish biomass, due to an artificial reef, has on fishing catch per unit effort (CPUE). This model can be used to identify the scenarios (in terms of reef, fish, and harvest characteristics) that pose the most risk of exploitation due to fish attraction. The properties of this model were compared to the long‐standing predictions by Bohnsack (1989) on the factors that increase the risk or the harm of attraction. Simulations revealed that attraction is not always harmful because it does not always increase maximum fish density. Rather, attraction sometimes disperses existing fish biomass making them harder to catch. Some attraction can be ideal, with CPUE lowest when attraction leads to an equal distribution of biomass between natural and artificial reefs. Simulations also showed that the outcomes from attraction depend on the characteristics of the target fish species, such that transient or pelagic species are often at more risk of harmful attraction than resident species. Our findings generally agree with Bohnsack's predictions, although we recommend distinguishing “mobility” and “fidelity” when identifying species most at risk from attraction, as these traits had great influence on patterns of harvest of attracted fish biomass.

Characterizing the three‐dimensional distribution of schooling reef fish with a portable multibeam echosounder

“…This pattern, known as the thigmotaxic response, or the tendency for animals to move toward structure rather than bare habitat, is a dominant process structuring the distribution of fishes (Brickhill et al 2005; Sheehan et al 2020), even when it acts to their detriment (Hallier and Gaertner 2008). In the context of artificial reefs, this process is the basis for the enduring “fish attraction” debate (Bohnsack 1989; Pickering and Whitmarsh 1997; Smith et al 2015).…”

Marine Ranching Construction and Management in East China Sea: Programs for Sustainable Fishery and Aquaculture

“…Take artificial reef construction as an example: artificial reefs are human-made structures installed in aquatic habitats that serve as a substrate and/or shelter for organisms, create exclusion areas to reduce the effort of industrial fishing and are considered as an important method for ecosystem restoration [17,41,42]. Artificial reef construction may have both positive and negative environmental implications [43,44]. Although artificial reef construction can create suitable habitats for introduced (or target) species or attracting fishes, such as rocky fish, the shift in the substrate from a soft substrate to a hard substrate may negatively impact non-target species and habitats [45,46].…”

Sunken Worlds: The Past and Future of Human-Made Reefs in Marine Conservation

“…The answer to this question is difficult to determine in most cases, and is unlikely to be binary (Pickering & Whitmarsh 1997). Attraction has almost universally been posited as a harmful process which makes fish more vulnerable to exploitation, but recent work indicates some attraction could be beneficial for some species as dispersion could make fish harder to catch (Smith et al 2015). Regardless of whether they are diverting biomass from natural structures or increasing it overall, HMRs are capable of sheltering high levels of biomass and biodiversity (Turner et al 1969;Claisse et al 2014), though they may vary in trophic structure from natural reefs (Simon et al 2013).…”