abundance of giant sea anemones and patterns of association with anemonefishin the northern red sea

Abstract

patterns of distribution and abundance of giant sea anemones and anemonefish were compared among coral reefs along the coastline of sinai in the northern red sea. the sea anemones varied widely in abundance between reef areas containing different habitat types. they were rare on steep reef slopes with abundant coral cover (=low-density anemone sites, 0.09–0.68 anemones per 1000 m2 of reef area), but were common at a site containing patch reefs interspersed with sand (=high-density anemone site, 6.00–8.11 anemones per 1000 m2). distributions of the endemic two-band anemonefish (amphiprion bicinctus) varied significantly between the two main host anemone species. at the high-density site, individuals of the sea anemone heteractis crispa either did not contain anemonefish, or were occupied by single juvenile fish as shown in previous studies. at low-density sites h. crispa usually hosted clusters of juvenile anemonefish. in contrast, individuals of the sea anemone entacmaea quadricolor hosted either single adult fish (high-density site) or pairs of breeding adults (low-density sites), frequently in addition to some juvenile fish. mechanisms that prevent anemonefish from reaching adult size and forming breeding pairs in h. crispa may include high fish mortality above a size threshold because this host cannot adequately protect them from predation when they become large, active emigration of fish to e. quadricolor as described in previous reports, and/or environmentally-controlled cessation of fish growth. we conclude that in the northern red sea, individuals of h. crispa potentially serve as nurseries for anemonefish.

Anemonefish oxygenate their anemone hosts at night

“…wedging, switching) when anemonefishes reside among sea anemone tentacles. Wild individuals of both A. bicinctus and E. quadricolor attain much larger maximum sizes than the individuals examined here, and in the Red Sea, each individual of E. quadricolor usually hosts a pair of adult fish plus up to three juveniles (Chadwick and Arvedlund, 2005;Huebner et al, 2012). The ecophysiological effects of anemonefish size, quantity and social structure on anemone hosts in the wild are largely unknown, and further investigation is needed to clarify the nocturnal behaviors of anemonefish in the wild.…”

Host preference and habitat segregation among Red Sea anemonefish: effects of sea anemone traits and fish life stages

“…However, some hosts appear to be more desirable than others, resulting in potential monopolization by competitively dominant individuals (Fautin 1986). Thus, breeding pairs of adult fish may defend certain types of anemones, while conspecific juvenile fish are relegated to other types of host anemones (Fautin 1991, Chadwick & Arvedlund 2005. However, the contributing factors and demographic impacts of this habitat segregation among anemonefish life stages are not well understood.…”

“…In contrast, the only documented benefit provided by sea anemones to anemonefishes is shelter from predation, to both the fish and their egg masses (Fautin 1991). Sea anemones vary in their traits that relate to sheltering fish, for example in terms of their chemical defenses (Elliott et al 1994), tentacle morphology (Fautin & Allen 1997), types of microhabitats occupied (Chadwick & Arvedlund 2005), and in the provision of nearby substratum for the incubation of fish egg clutches (Allen 1972). Anemonefishes potentially compete for preferred host species based on these factors, causing their distributional patterns to differ from those expected based on host and fish abundances alone (Srinivasan et al 1999).…”

“…In the Gulf of Aqaba, northern Red Sea, endemic 2-band anemonefish Amphiprion bicinctus mainly occupy bulb-tentacle sea anemones Entacmaea quadricolor and leathery sea anemones Heteractis crispa (Chadwick & Arvedlund 2005). H. crispa are solitary with long, thin tentacles, and mainly host juveniles of A. bicinctus (Fishelson 1970, Chadwick & Arvedlund 2005, while E. quadricolor possess thicker tentacles that may be long and digitiform or short and bulbous (Dunn 1981).…”

Ecological Studies on Two Amphiprion Species in Maldivian Coral Reefs

“…34, 5020 Salzburg, Austria; Tel +43 662 8044 5619; Fax +43 662 8044 5698; E-mail; robert.patzner@sbg.ac.at length of 70 m for each transect. The following parameters were considered: species of Amphiprion, species of anemone, size of the anemone, water depth (in strata of 1 -4.9 m, 5 -9.9 m, and 10 -15 m), number of adult Amphiprion, number of juvenile Amphiprion (3 size classes), and number of host anemone per 1,000 m (with reference to Chadwick JMBA 2005) [8]. The size of an anemone was determined by measuring the lengths between the tentacle tips on both the long and short axes.…”