The intensity of kelp harvesting shapes the population structure of the foundation species Lessonia trabeculata along the Chilean coastline

Abstract

Kelp are foundation species that support high levels of biodiversity and, either directly or indirectly provide a wide range of ecological goods and services to human society. In recent decades, due to the high demand for kelp-derived products such as alginate, commercial wild harvesting has increased, leading to declines of kelp biomass in some regions. Chile accounts for 40% of the global kelp harvest, with the subtidal kelp, Lessonia trabeculata being one of the main target species. Currently, however, there is a lack of information on how different degrees of harvesting intensity, governed by distinct management regimes and their enforcement influences L. trabeculata populations. Here we examined the effect different management regimes, characterised by distinct levels of exploitation of kelp and kelp-associated fauna, have on L. trabeculata density and morphology along ~ 1600 km of the Chilean coastline. The findings demonstrated that harvesting intensity likely influences both L. trabeculata density and morphology. Juvenile density of L. trabeculata was five times higher in the most harvesting-affected areas, while kelp morphology values, including holdfast diameter, number of stipes and total length, were always higher in the less-intensively harvested areas. Our study suggests that different degrees of protection can influence density and morphology of subtidal L. trabeculata populations, which in turn has important implications for the conservation of the kelp forest ecosystems and management of this important fishery.

One of the least disturbed marine coastal ecosystems on Earth: Spatial and temporal persistence of Darwin’s sub‐Antarctic giant kelp forests

“…Molecular studies have suggested a northern hemisphere origin of giant kelp, with a later dispersal to the southern hemisphere (Astorga et al, 2012;Coyer et al, 2001;Macaya & Zuccarello, 2010). Specifically, Coyer et al (2001) indicate that multiple inter-hemisphere crossings occurred be- (Gouraguine et al, 2021;Krumhansl et al, 2016;Vásquez, 2008).…”

Different kelp species support unique macroinvertebrate assemblages, suggesting the potential community‐wide impacts of kelp harvesting along the Humboldt Current System

“…Chile (Vásquez & Santelices, 1990;Vásquez et al, 2013;Gouraguine et al, 2021). Currently, around 40,261 tons are harvested per year (SERNAPESCA, 2020), with this species in high demand owing to its high alginate (structural polysaccharides) content, which is widely used in a variety of industries, as well as being used as feed in abalone cultivation (Buschmann et al, 2014;Méndez Ancca et al, 2018).…”

Effects of harvesting on subtidal kelp forests (Lessonia trabeculata) in central Chile

“…The study was conducted in an open access area at Quintay, which is located in the influence of the main upwelling center of Curaumilla (Tapia et al, 2009; Tapia et al, 2014; Wieters, 2005). Here, L. trabeculata forests extend almost continuously along the shallow hard‐bottomed subtidal from ~5 to ~30 m depth and have an average adult density of approximately two individuals per square meter (Gouraguine et al, 2021; Pérez‐Matus, Ospina‐Alvarez, et al, 2017; Vásquez, 1992). Subtidal kelp harvesting is not yet practiced at this particular site (Quintay), and thus, potential artifacts of previous harvesting events, as well as conflict with local fishermen, were avoided.…”

“…Fishers (both in our experiment and elsewhere) selectively target large kelp holdfast (>30 cm diameter) (Gouraguine et al, 2021), which are known to support up to six times more diversity and abundance of associated fauna than juvenile (nontarget) holdfasts and facilitates the co-occurrence of more than 100 different species (Carbajal et al, 2021). Therefore, the impacts of this fishery to associated community are potentially wide and our findings are congruent with those harvesting on associated communities in intertidal kelp ecosystem (Cancino & Santelices, 1984) and other in subtidal kelp species (Norderhaug et al, 2020) revealing the need to incorporate the ecosystem-level effects of this fishery into the management of kelp harvesting species.…”

“…Consumer presence during recovery also altered spatial distribution of kelp recruits and the frequency of coalescence (Oróstica et al, 2014). Thus, a number of specific harvesting recommendations have been proposed to reduce the negative effects of kelp harvesting on the recovery of kelp forests (Gouraguine et al, 2021; Vásquez, 2008; Westermeier et al, 2018). Knowledge of community‐wide effects of harvesting of subtidal kelp ( L. trabeculata ) is relatively scarce and more limited to coincidental temporal observations.…”