Egg production patterns of two invertebrate species in rocky subtidal areas under different fishing regimes along the coast of central Chile

Abstract

Fishing is a major source of human impact, reducing density and size of a wide range of exploited species in comparison to areas exhibiting strong regulations (no-take and partially protected areas, including Territorial Use Rights for Fisheries, TURFs). Since size and density might have important consequences on reproduction, and therefore natural re-seeding, we monitored adult size, density and potential fecundity of the keyhole limpet (Fissurella latimarginata) and the red sea urchin (Loxechinus albus) in areas under two fishing regimes (TURFs and Open Access Areas, OAAs). Analyzing the distribution of suitable habitats, we predict spatial patterns of potential egg production, to identify reproductive hotspots along the central coast of Chile. The current system of TURFs in central Chile showed higher potential egg production of F. latimarginata and of L. albus than expected under a complete OAAs scenario (67 and 52% respectively). Potential egg production showed more than a twofold reduction when the complete TURFs scenario was compared against complete OAAs condition in both species. Individual size and density explained between 60% and 100% of the variability in potential egg production, suggesting the importance of the enhancement of both biological variables in TURFs in Chile. Potential egg production for both species in the northern part of the studied domain was higher due to the combined effect of (a) suitable habitat and (b) concentration of TURFs. Our results suggest that partially protected areas, such as TURFs can significantly enhance the production of propagules that could seed exploited areas.

Integration of biophysical connectivity in the spatial optimization of coastal ecosystem services

“…Habitat distribution was obtained by characterizing the habitat type (rock vs. sand) in each of the latitudinal cells using high resolution satellite photography (Fig.1, left panel) for the intertidal zone and projecting this onto a uniform shallow subtidal band down to a depth of 200 m. Combined, these two data sources describe the proportion of rocky coast covered by MA in each cell. The remaining fraction of rocky coast in each cell was assumed to be open access (hereafter OA; see Blanco et al, 2017, for details).…”

“…Based on these studies (see Blanco et al, 2017Blanco et al, , 2019, for details), we estimated that net larval production in MAs was 17% less than in NT areas, which was the baseline (Table 1). Scale factors to estimate L in open access areas were calculated for each species from field work and laboratory experiments (see Blanco et al, 2017). Afterwards, L per cell was estimated based on potential fecundity per unit of rocky area for the different fishing regimes (see Blanco et al 2017 and eqs.…”

Comanagement of small‐scale fisheries and ecosystem services

“…In open access areas, it has been estimated that 22 million larvae are released every 90 m 2 . On the other hand, in TURFs, a 20‐fold increase in release of larvae is estimated (Blanco, Ospina‐Alvarez, Gonzalez, & Fernandez, ). Other invertebrate benthic species of commercial importance (the keyhole limpet Fissurella latimarginata and the red sea urchin Loxechinus albus ) also have higher potential fecundity within TURFs than in open access areas as they reach larger size and consequently produce larger gonads (Fernandez, Blanco, Ruano‐Chamorro, & Subida, ).…”

“…In open access areas, it has been estimated that 22 million larvae are released every 90 m 2 . On the other hand, in TURFs, a 20-fold increase in release of larvae is estimated (Blanco, Ospina-Alvarez, Gonzalez, & Fernandez, 2017).…”

Drivers and trends in catch of benthic resources in Chilean TURFs and surrounding open access areas

“…TURFs are expected to secure fisheries harvests within their boundaries and provide incentives for sustainable use of surrounding fishing grounds (Christy 1982). Recent studies in the Chilean system of TURFs have shown higher potential egg production of two benthic species (the limpet Fissurella latimarginata and the red sea urchin Loxechinus albus) within TURFs than under an open access scenario (67% and 52% higher, respectively) (Blanco et al 2017), suggesting the potential to enhance fishing opportunities both inside and outside TURFs. Negative impacts of TURFs and other entry-restriction management and conservation tools beyond their limits are less well known.…”