Ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfishScarus zelindae

Abstract

Parrotfish are fundamental species in controlling algal phase-shifts and ensuring the resilience of coral reefs. Nevertheless, little is known on their ecological role in the south-western Atlantic Ocean. The present study analysed the ontogenetic foraging activity and feeding selectivity of the Brazilian endemic parrotfish Scarus zelindae using behavioural observation and benthic composition analyses. We found a significant negative relationship between fish size and feeding rates for S. zelindae individuals. Thus, terminal phase individuals forage with lower feeding rates compared to juveniles and initial phase individuals. The highest relative foraging frequency of S. zelindae was on epilithic algae matrix (EAM) with similar values for juveniles (86.6%), initial phase (88.1%) and terminal phase (88.6%) individuals. The second preferred benthos for juveniles was sponge (11.6%) compared with initial (4.5%) and terminal life phases (1.3%). Different life phases of S. zelindae foraged on different benthos according to their availability. Based on Ivlev’s electivity index, juveniles selected EAM and sponge, while initial phase and terminal phase individuals only selected EAM. Our findings demonstrate that the foraging frequency of the endemic parrotfish S. zelindae is reduced according to body size and that there is a slight ontogenetic change in feeding selectivity. Therefore, ecological knowledge of ontogenetic variations on resource use is critical for the remaining parrotfish populations which have been dramatically reduced in the Southwestern Atlantic Ocean.

Effects of depth on reef fish communities: Insights of a “deep refuge hypothesis” from Southwestern Atlantic reefs

“…For instance, interviews with local fishermen from the site evaluated in the present study confirmed this trend for many reef fish species, especially for Scarus trispinosus , an endemic and endangered parrotfish. This species is virtually extinct locally in shallow reefs, but being recorded at high abundance in the last decades [ 38 ].…”

“…On the other hand, Carapitanga (8° 49'35.59 "S 35° 2'43.16" W) and Carapitanga do Norte (8° 49'13.58 "S and 35° 2'21.60" W) were the deep reefs. They are reefs more distant from the main land (around 8 km) and had a depth ranging from 25 to 30 m ( Fig 1 , also see [ 38 ] for site description).…”

“…Brazilian coral reefs are approximately extended 3,000 km along the Brazilian coast, disconnected from the Caribbean Sea by a semi-permeable geographic barrier [ 35 ]. Recent studies have described the composition and community structure of deeper reefs in Brazil [ 25 , 36 , 37 ] However, the deep refugee hypothesis has been poorly studied on Brazilian reefs [ 25 ] and preliminary data on our deeper study sites suggests that fish populations could be buffered from shallow waters impacts [ 38 ].…”

Novel field observations of coral reef fishes feeding on epiphytic and epizoic organisms associated with the allelopathic seaweed Galaxaura divaricata

“…It is often assumed that when fish feed on a macroalga that it is the alga they are eating. This view led to the perception that parrotfishes eat macroalgae, including turf (e.g., Adam et al, 2015 ; Feitosa & Ferreira, 2015 ; Pereira et al, 2016 ). Our feeding observations indicate that while juvenile parrotfishes, i.e., Scarus schlegeli , S. ghobban , S. rivulatus , and Chlorurus spilurus , took many small bites from G. divaricata , they did not appear to consume the thallus itself.…”

Age, growth, reproduction and management of Southwestern Atlantic’s largest and endangered herbivorous reef fish, Scarus trispinosus Valenciennes, 1840

“…Up until the 1980’s parrotfishes were rarely captured by recreational fishers and were not targeted by commercial fisheries. However, in the mid 1990’s parrotfish captures intensified in Northern and Northeastern Brazil (Ferreira et al, 2012; MMA, 2014; Roos et al, 2015), with widespread usage of gillnets, traps and spears, followed by a remarkable abundance decline of S. trispinosus at all studied locations (e.g., Francini-Filho & Moura, 2008a; Francini-Filho & Moura, 2008b; Bender et al, 2014; Pereira et al, 2016). Its population is estimated to have declined by >50% over the past three decades, and S. trispinosus is currently considered one of the world’s most endangered parrotfishes (Comeros-Raynal et al, 2012).…”