Effect of foresting barren ground with Macrocystis pyrifera (Linnaeus) C. Agardh on the occurrence of coastal fishes off northern Chile

Abstract

Macrocystis pyrifera kelp beds play a significant ecological role along the coast of Chile. Besides their importance as food, protection structures, substrata, microhabitats and nurseries, regularly occurring natural disturbances (e.g. extremes of the climate variability El Niño-Southern Oscillation) and increased kelp exploitation affect these habitats. The present study aimed to test the dependence of reef fishes on Macrocystis pyrifera and to evaluate the effect of an enhanced habitat structure (experimental M. pyrifera bed) on the abundance, composition and spatial distribution on rock, on macroalgae, in the water column and on sand of the reef fish community. Boulders colonised by M. pyrifera were transported into three replicated experimental areas (9 m 2 each) located in a barren ground area. Three barren ground areas (9 m 2 each) without manipulation were selected as controls. The fish abundance, composition and spatial distribution on rock, on macroalgae, in the water column and on sand were recorded weekly by scuba diving over a period of 3 months, between 15 February 2007 and 13 June 2007 (4 months). Results indicate significantly higher abundances (mean = 225%) of fishes in the forested areas compared to the barren ground controls (mean = 3.71 fishes/9 m 2 and 1.14 fishes/9 m 2 , respectively). Scartichthys gigas/viridis, Chromis crusma, Cheilodactylus variegatus and Isacia conceptionis numerically dominated the fish assemblages of the experimental kelp patches. Each fish species revealed different distributions in the forested areas: Scartichthys gigas/viridis was more abundant on rocks and C. variegatus in the macroalgae, whereas C. crusma and I. conceptionis preferred the water column above the experimental kelp bed. During the experimental time, the kelp lost some blades and some plants became detached. The overall number of fishes correlated with the declining kelp abundance (r = 0.964, p < 0.05). The fish species showed different responses to these changes in the experimental areas: C. variegatus and I. conceptionis declined in abundance, whereas the abundance of Scartichthys gigas/ viridis remained constant.

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

“…Fish assemblages observed here were composed of typical species from the Chilean coast. The comparatively low total number of fish species per site was similar to SR of reef-fish observed by other studies along the central and northern coast of Chile (Gelcich et al, 2008; Ory et al, 2012; Villegas et al, 2018). Pérez-Matus et al (2007) studied the structure of fish assemblages in northern Chile and found that CA was the site with the highest SR.…”

“…These species are common in northern Chile and display variable colour patterns (Méndez-Abarca & Mundaca, 2016), making it sometimes difficult to distinguish among them, especially in videos with limited visibility. As both species are of similar size and ecological habits, we treated them as Scartichthys viridis/gigas (see also Villegas et al, 2018).…”

“…In order to fill this gap, we compared the effect of coastal fishes in kelp forests and on barren grounds in northern-central Chile by surveying fish assemblages and estimating predation on tethered live prey organisms in these contrasting habitats. Kelp forests are structurally complex systems that tend to have greater richness and abundance of predatory species compared to less complex systems (Hauser, Attrill & Cotton, 2006; Miller et al, 2018; Villegas et al, 2018) such as barren grounds (Sala & Zabala, 1996; Norderhaug & Christie, 2009). Therefore, we expected to find higher species richness (SR) and abundances of predatory fish in kelp forests than on barren grounds, and hence higher predation pressure on our baits at sites with a greater presence of predators.…”

Kelp Forest Zooplankton, Forage Fishes, and Juvenile Salmonids of the Northeast Pacific Nearshore

“…; Villegas et al. ). Kelps are also sensitive to human activities, such as changes in water quality (Vergés et al.…”

“…In many systems, kelp beds alter water flow and provide important habitats for adult and juvenile fish by increasing structural complexity that offers refuge from predators and production of fish prey (Wharton and Mann 1981;Duggins 1988;Holbrook et al 1990;Norderhaug et al 2005). Kelp can be a major driver of patterns in fish and zooplankton presence (Holbrook et al 1990;Villegas et al 2019). Kelps are also sensitive to human activities, such as changes in water quality (Vergés et al 2016) or predator removals that cause trophic cascades (Estes and Palmisano 1974).…”