Coastal fish assemblages and predation pressure in northern-central Chilean Lessonia trabeculata kelp forests and barren grounds

Abstract

Kelp forests are declining in many parts of the globe, which can lead to the spreading of barren grounds. Increased abundances of grazers, mainly due to reduction of their predators, are among the causes of this development. Here, we compared the species richness (SR), frequency of occurrence (FO), and maximum abundance (MaxN) of predatory fish and their predation pressure between kelp forest and barren ground habitats of northern-central Chile. Sampling was done using baited underwater cameras with vertical and horizontal orientation. Two prey organisms were used as tethered baits, the black sea urchin Tetrapygus niger and the porcelanid crab Petrolisthes laevigatus. SR did not show major differences between habitats, while FO and MaxN were higher on barren grounds in vertical videos, with no major differences between habitats in horizontal videos. Predation pressure did not differ between habitats, but after 24 h consumption of porcelanid crabs was significantly higher than that of sea urchins. Scartichthys viridis/gigas was the main predator, accounting for 82% of the observed predation events on Petrolisthes laevigatus. Most of these attacks occurred on barren grounds. Scartichthys viridis/gigas was the only fish observed attacking (but not consuming) tethered sea urchins. High abundances of opportunistic predators (Scartichthys viridis/gigas) are probably related to low abundances of large predatory fishes. These results suggest that intense fishing activity on large predators, and their resulting low abundances, could result in low predation pressure on sea urchins, thereby contributing to the increase of T. niger abundances in subtidal rocky habitats.

DNA reconciles morphology and colouration in the drunk blenny genus Scartichthys (Teleostei: Blenniidae) and provides insights into their evolutionary history

“…(2020), different colour morphs of S. viridis have been observed together inhabiting the same environments. This colour polymorphism could thus be related to either juvenile stages or microhabitat preferences as both colour morphs are associated with algae (Pérez‐Matus et al ., 2017a; Riquelme‐Pérez et al ., 2019). This study also allowed the authors to depict the evolutionary history of the Scartichthys genus.…”

“…In addition, they are known among local fishermen as “borrachillas” (drunk) because the consumption of the flesh of these fish leads to a sleepy or drunk feeling (Méndez‐Abarca & Mundaca, 2016; Williams, 1990). Despite these interesting aspects of their ecology, Scartichthys blenniids remain difficult (Pérez‐Matus et al ., 2007; Riquelme‐Pérez et al ., 2019) or even impossible to identify at the species level in the field (Villegas et al ., 2019). Identification is especially challenging across the 6000 km where three recognized species are known to occur in sympatry.…”

DNA reconciles morphology and colouration in the drunk blenny genusScartichthys(Teleostei: Blenniidae) and provides insights into their evolutionary history

“…In line with Gaither et al (2020), different colour morphs of S. viridis have been observed together inhabiting the same environments. This colour polymorphism could thus be related to either juvenile stages or microhabitat preferences as both colour morphs are associated with algae (Prez-Matus et al, 2017;Riquelme-Prez et al, 2019).…”

“…Additionally, they are known among local fishermen as borrachillas [drunk] because the consumption of the flesh of these fish leads to a sleepy or drunk feeling (Williams, 1990;Mndez-Abarca & Mundaca, 2016). Despite these interesting aspects of their ecology, Scartichthys blenniids remain difficult (Prez-Matus et al, 2007;Riquelme-Prez et al, 2019) or even impossible to identify at the species level in the field (Villegas et al, 2019). Identification is especially challenging across the 6000 km where three recognized species are known to occur in sympatry.…”

Small burrowing amphipods cause major damage in a large kelp

“…Alternatively, epifaunal invertebrates may avoid the basal sections of large kelp thalli to escape intense predation from benthic predators. Demersal fishes prey intensively on benthic invertebrates in kelp forests of northern-central Chile [44]. Accordingly, the nest-building amphipod S. femorata predominantly lives on the apical blades of giant kelp M. pyrifera where the amphipods suffer less predation than on basal blades [45].…”