Spawning aggregations:patterns of movement of the coral trout Plectropomus leopardus (Serranidae) as determined by ultrasonic telemetry

Abstract

ABSTRACT-This study measured biological variables necessary for determining the dynamics of spawning aggregations and measured the influences of these variables on effects of fishing on these aggregations. Four major spawning aggregation sites of Plectropomus leopardus (Serranidae) were identified at Lizard Island, Northern Great Barrier Reef, Australia, using ultrasonic telemetry. Spawning aggregation activities displayed a lunar pattern, with peak activities during new moon periods in the austral spring-early summer. Of 35 fish tracked during spawning periods in 1993-95, only 31 'in participated in spawning aggregations, despite all specimens being sexually mature. All specimens that aggregated displayed fidelity to their chosen aggregation site. The distance between established home ranges and spawning aggregation sites ranged from 220 to 5210 m, with total spawning movements back and fol th for individual fish ranging from 600 m to over 17 km. One-way inter-reefal movements were recorded for 3 fish moving 3, 7.5, and 11 km between ~e l e d s e dnd recdpture locdtiuns. Male fish spent an average of 8 times longer at aggregations than females. Females (n -4 ) undertook single-day or overnight trips only, while males (n = 8) often did multl-day tl-ips Males were also more likely to make several trips to spa\vning aggregation sites than females S~n c e males spent more time at aggregation sites, and made more trips to those sites, they we!-e potentially more vulnerable to fishing pressure on aggregations. The reliance on several aggregation sites per reef makes P. leopardus potentially less vulnerable to overexploitation of spawning aggregations. However, the strong site fidelity observed makes indiv~dual aggregations vulnerable to depletion. The low participation rate of reproductively mature individuals at major aggregation events (31 ",O) suggested that not all spawning activity took place at the known aggregation sites.

Detailed demographic analysis of an Epinephelus polyphekadion spawning aggregation and fishery

“…10% of the marketed volume in Kolonia . While marketed mature fish likely represent >1 reproductive population, those from Kehpara are considered to be from a single reproductive population, based on documented high spawning-site fidelity of this and other aggregating groupers (Zeller 1998, Johannes et al 1999, Starr et al 2007.…”

“…Of the 2, only the Kehpara aggregation has been examined in detail (Rhodes & Sadovy 2002b). Each of these aggregations is considered to entertain separate reproductive populations, based on previous indications of high spawning-site fidelity for this and other aggregating groupers (Zeller 1998, Johannes et al 1999, Bolden 2000, Starr et al 2007). In late 1999, the Kehpara aggregation experienced intense fishing pressure that resulted in the removal of thousands of individuals (Rhodes & Sadovy 2002b).…”

Ontogenetic changes in the diet of the coral reef grouper Plectropomus leopardus (Serranidae):patterns in taxa, size and habitat of prey

“…The coral trout fishery is the most valuable fin-fishery on the GBR (Williams & Russ 1994), representing about 30"4 of the total catch of the commercial line-fishing industry in Queensland (4000 metric tonnes in 1989, Trainor 1991). Due to their commercial importance, research on the biology of coral trouts has recently received much attention on the GBR (Doherty et al 1994, Ferreira & Russ 1994, Russ et a1 1996, Light & Jones 1997, Samoilys 1997, Zeller 1998) and much of this work has focused on the adults in the fishery (but see Doherty et a1 1994, Light 1995, Light & Jones 1997). Yet, information on all stages of their life history is necessary to understand the ecology of coral trouts.…”

Intra- versus inter-annual variation in counts of reef fishes and interpretations of long-term monitoring studies

“…For reef fishes, temporary changes in local distributions typically will result from sampling at scales less than the home range of the fish being counted. Such effects will be exacerbated where short-term shifts in the area of habitat occupied occur because of factors such as foraging behaviour (Ogden & Buckman 1972, Gladfelter 1979, Zeller 1997) and responses to tidal (Bray 1981), diurnal (Helfman 1986, Galzin 1987, and seasonal or spawning cycles (Samoilys & Squire 1994, Samoilys 1997, Zeller 1998. Sampling error might arise also because fishes move across the boundaries of sampling units during the time taken to survey the units, even though they do not move away from the sampling site, or react positively or negatively to the presence of an observer (Fowler 1987, Kulbicki 1998.…”