Abstract
Potential interactions between marine predators and humans arise in the southern coast of Chile where predator feeding and reproduction sites overlap with fisheries and aquaculture. Here, we assess the potential effects of intensive salmon aquaculture on food habits, growth, and reproduction of a common predator, the spiny dogfish—identified as Squalus acanthias via genetic barcoding. A total of 102 (89 females and 13 males) individuals were collected during winter and summer of 2013–2014 from the Chiloé Sea where salmon aquaculture activities are concentrated. The low frequency of males in our study suggests spatial segregation of sex, while immature and mature females spatially overlapped in both seasons. Female spiny dogfish showed a functional specialist behavior as indicated by the small number of prey items and the relative high importance of the austral hake and salmon pellets in the diet. Immature sharks fed more on pellets and anchovies than the larger hake‐preferring mature females. Our results also indicate that spiny dogfish switch prey (anchovy to hake) to take advantage of seasonal changes in prey availability. Despite differences in the trophic patterns of S. acanthias due to the spatial association with intensive salmon farming, in this region, there appears to be no difference in fecundity or size at maturity compared to other populations. Although no demographic effects were detected, we suggest that a range of additional factors should be considered before concluding that intensive aquaculture does not have any impact on these marine predators.
Highlights
In the past three decades, salmonid aquaculture in Chile has experienced an explosive growth and diversification driven by the use of intensive farming techniques (Buschmann et al, 2009; Oddone, Paesch, & Norbis, 2015) and the introduction of several different salmonid species (Correa & Gross, 2008)
Interactions between marine predators and humans arise in coastal ecosystems in various parts of the world where feeding and reproduction sites overlap with economic activities such as fisheries and aquaculture
These interactions include (1) mortality through bycatch; (2) deliberate harming of animals by humans; (3) changes in animal behavior; (4) competition for the same resource; (5) changes in prey size structure and distribution; and (6) changes in community composition resulting from fishing or from aquaculture-induced alterations of the environment (De La Torriente et al, 2010; Guilpart et al, 2012; Kemper et al, 2003; Kutti et al, 2007; Papastamatiou et al, 2010; Ribeiro et al, 2007; Sepúlveda & Oliva, 2005; Sepulveda et al, 2007; FIGURE 4 Reproductive biology of Squalus acanthias females in the Chiloe Sea. (a) Allometric relationship between the total weight and total length of spiny dogfish
Summary
In the past three decades, salmonid aquaculture in Chile has experienced an explosive growth and diversification driven by the use of intensive. In Chile, the salmon industry is concentrated around the inner sea of Chiloé Island (41–43°S, hereafter Chiloé Sea) (Figure 1) (Buschmann et al, 2006, 2009) This region is a semi-closed environment that is home to rare, unique and endangered marine species, including cold- water corals (Försterra & Häussermann, 2003), penguins and migratory birds (Senner et al, 2014; Skewgar, Boersma, & Simeone, 2014), otters (Ebensperger & Botto-Mahan, 1997), blue and humpback whales (Hucke-Gaete et al, 2004), dolphins and pinnipeds (Ribeiro et al, 2007; Veríssimo et al, 2010), and skates and sharks (Lamilla et al, 2005; Quiroz, Wiff, & Céspedes, 2009; Valenzuela, Bustamante, & Lamilla, 2008). We discuss the trophic and reproductive metrics employed here in the context of S. acanthias populations elsewhere, which are unexposed to intense salmonid aquaculture
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