Selection of diurnal refuges by the nocturnal squirrelfish, Holocentrus rufus

Abstract

We examined the diurnal refuges occupied by the nocturnal squirrelfish, Holocentrus rufus, to describe refuges and the behavior associated with their use and to determine which, if any, refuge characteristics were selected. We tagged 21 H. rufus on two sites on a fringing reef in Barbados, West Indies, identified the refuges they used (n = 57), measured ten characteristics of each refuge and the surrounding microhabitat, and monitored their refuge use for 4 weeks. To evaluate refuge selection, we measured the same characteristics on a comparable number of unused potential refuges (n = 67) on the same reefs and used classification tree models to determine which characteristics separated used from unused refuges. Each fish used 1-9 refuges, which did not overlap among individuals and were defended against intrusion by conspecifics and some heterospecifics. Fish with more than one refuge frequently moved among them. There was strong site fidelity with no immigration of untagged fish or emigration of tagged fish on either reef during the study period and no additional refuges being occupied over the 4-week period. Refuges were primarily holes, open at one or two ends, which varied in size, distance from the reef edge, entrance orientation, and vertical relief at the entrance. Holes used as refuges differed significantly from unused holes mainly in characteristics related to the vertical position of their entrance, but the classification tree models differed for the two sites. This study provides the first detailed information on characteristics of daytime refuges used by a nocturnally active reef fish and the first evidence of selectivity of refuges. It suggests that the abundance and characteristics of holes on reefs could influence the density of H. rufus on natural reefs.

How American eels Anguilla rostrata construct and respire in burrows

“…Substrate occupancy may reduce the risk of predation, protect against strong currents, or serve as a base for feeding (Bozzano 2003, Ménard et al 2008. Yellow-stage anguillid eels generally forage nocturnally, but spend the day in the substrate, either in burrows excavated in soft sediments, or in spaces among rocks or bottom debris (Glova 2002, Tesch 2003.…”

“…Some fish species spend much or most of their time in the substrate, either in self-dug burrows (Atkinson & Taylor 1991) or in natural cavities (Ménard et al 2008). Substrate occupancy may reduce the risk of predation, protect against strong currents, or serve as a base for feeding (Bozzano 2003, Ménard et al 2008.…”

A passive acoustic survey of fish sound production at Riley’s Hump within Tortugas South Ecological Reserve; implications regarding spawning and habitat use

“…Sound production is common among many fishes and is associated most often with courtship and spawning behaviors (Mok and Gilmore, 1983). Because sounds are species-specific, once the source has become positively identified, the information can be referenced to all future recordings to identify the presence of a given species at a monitoring site.…”

“…Because sounds are species-specific, once the source has become positively identified, the information can be referenced to all future recordings to identify the presence of a given species at a monitoring site. Time series from the acoustic monitoring of fish sound production, therefore, can be used as a proxy to document the timing and location of reproductive behavior (Locascio and Mann, 2008). Recording technologies now allow multiyear deployments during which short periods of data (e.g., tens of seconds) may be recorded every few minutes.…”

“…Thus far, the sounds of Atlantic goliath grouper (E. itajara), red hind, red grouper, yellowfin grouper (M. venenosa), Nassau grouper, and black grouper have been positively identified and correlated with known spawning seasons (Mann et al, 2009;Mann et al, 2010;Nelson et al, 2011;Schärer et al, 2012Schärer et al, , 2013. Other grouper species are also likely to produce sound, and these sounds await discovery.…”