Aggregation and spawning of the humphead wrasse Cheilinus undulatus (Pisces: Labridae): general aspects of spawning behaviour

Abstract

The humphead wrasse Cheilinus undulatus formed resident spawning aggregations daily after high tide at specific locations along the seaward edge of the Palau barrier reef. The location and extent of one aggregation site remained consistent for 6 years with no physical features distinguishing it from adjacent areas. Spawning was documented most months and probably occurred year round with possible seasonal and lunar variation. Spawning males arrived first at the site, followed by females and potentially small primary males. The aggregation female to male sex ratio was estimated to be between 6:1 and 10:1. A maximum of 15 males and 100-150 females were observed at the site. A male courtship posture with the anal fin pointed, the caudal fin folded down and the dorsal fin folded against the body was maintained while swimming a few metres off the bottom in view of females. When ready to spawn females rose up as the posturing male passed and the pair released gametes in a relatively sedate fashion near the surface along the shelf break. No attempted predation on spawning adults was seen. Egg predation after spawning was uncommon. On days with early to mid-day high tides the spawning period started 2·0-2·5 h after high tide when the speed of lagoon-ocean tidal currents peaked and lasted c. 1 h. On days with later afternoon high tides, spawning occurred sooner after high tide and before current speeds peaked. Other fishes with planktonic eggs spawned at the site as pairs or small groups in a rough succession after high tide with C. undulatus, the last species to spawn.

The IUCN Red List of Threatened Species: an assessment of coral reef fishes in the US Pacific Islands

“…Further, the life history characteristics of many species render them particularly vulnerable to overexploitation. Many large-bodied species tend to be slow-growing, long-lived, have delayed reproductive development, and some form mass aggregations when they spawn (Choat et al 2006;Tupper 2007;Sadovy de Mitcheson et al 2008;Colin 2010). Large-bodied species play a critical role in structuring marine ecosystems (Bascompte et al 2005;Estes et al 2011), and severe reductions in their biomass have detrimental ecological and economic effects (Pauly et al 1998;Jackson et al 2001;Friedlander and DeMartini 2002;Myers and Worm 2003;Sandin et al 2008).…”

Umbrella species in marine systems: using the endangered humphead wrasse to conserve coral reefs

“…The humphead wrasse eats a wide variety of invertebrate and teleost fish prey, and is notable in being one of the few predators of Acanthaster planci, the crown-of-thorns starfish (Randall et al 1978, Sadovy et al 2003a. Despite the large observation effort by scientists, divers, and fishers, understanding of its spawning behavior was only recently developed (Colin 2010). Only one publication exists on home range and movement (Chateau & Wantiez 2007), limited to a single individual that departed the small study region after 25 d, compromising the estimate of home range.…”

“…We then compared the HRL with class using an ANOVA to check if differences in HRL could be detected between classes. The possibility of primary males < 85 cm TL exists (Colin 2010, Sadovy de Mitcheson et al 2010), so we cannot rule out the possibility that individuals categorized as female were small primary males. In addition, the existence of rare large females (Sadovy de Mitcheson et al 2010) means there is a possibility that individuals we classified as male were actually female.…”

Gonadal development in a giant threatened reef fish, the humphead wrasse Cheilinus undulatus, and its relationship to international trade

“…Minimum size for females to spawn in captivity was reported at c. 500 mm L T at grow‐out facilities in Indonesia. In Palau, Micronesia, and Layang Layang, Malaysia, the minimum sizes of female sexual maturation were estimated visually at c. 350–450 mm L T , based on observations of female spawning underwater (TRACC, 2004; Colin, 2010). Specimens from Indonesia and PNG included few specimens of the size range of 450–550 mm L T , most were either much larger (PNG; Sadovy et al , 2003 a ) or smaller (Indonesia, this study).…”