aqua, International Journal of Ichthyology The return of the yellow grouper – annual migration and return to the same site by a xanthistic Mycteroperca fusca (Pisces: Serranidae) Peter Wirtz Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, PT 8005-139 Faro, Portugal. E-mail: [email protected] Received: 25 March 2007 – Accepted: 13 September 2007 Abstract place every year after its annual migration. Follow - The homing behaviour of an individually recognizable ing Saldanha (1979), they called the species Epi - Mycteroperca fusca has been observed in the field over a time nephelus alexandrinus but in reality it is Mycteroperca span of 25 years. The animal leaves the bay of Garajau on fusca (Heemstra 1991, Heemstra & Randall 1993). the south coast of Madeira Island in spring and returns every Waschkewitz & Wirtz (1990) were able to recognize year in autumn. This is the first long-term study showing that a fish returns to the same place annually, in a manner the fish individually because of its unique colour similar to migratory birds. pattern: in contrast to the normal brown-silver colour of the species (Fig. 1), it is bright yellow with Zusammenfassung white blotches on the lips, the belly, and the fins Das Heimkehrverhalten eines individuell erkennbaren (Figs 2 and 3). Waschkewitz & Wirtz (1990) Exemplars von Mycteroperca fusca konnte über 25 Jahre im showed that, during a time span of eight years, this Freiland beobachtet werden. Das Tier verlässt die Garajau- individual left the bay of Garajau on the south coast Bucht an der Südküste von Madeira im Frühjahr und of Madeira Island in spring and returned to it in kehrt jedes Jahr im Herbst zurück. Dies ist der bisher autumn. Here I extend the observation time of this einzige Fall der Langzeitbeobachtung der jährlichen Rück - kehr eines Fisches an denselben Ort, vergleichbar dem Ver - remarkable behaviour to 25 years. halten von Zugvögeln. MATERIALS AND METHODS Résumé Observations were made from 1981 to 2006 while Le comportement d’aller et retour d’un Mycteroperca fusca SCUBA diving in the bay of Garajau, south coast of reconnaissable comme individu a été observé sur le terrain Madeira Island, and in other areas up to 20 km east pendant une période de 25 ans. Le poisson quitte la baie de and west of this bay. The bay of Garajau was declared Garajau, sur la côte sud de l’île de Madeire, chaque année a Nature Reserve in 1986. Customers of four com - au printemps et revient chaque année en automne. Il s’agit mercial SCUBA diving bases are diving in it almost ici de la première étude de longue durée qui montre qu’un poisson retourne annuellement au même endroit, d’une daily. The first sighting of the xanthistic Mycteroperca façon similaire à celle des oiseaux migrateurs. fusca each autumn was noted by the author or com - municated to him by the staff of these commercial Sommario SCUBA diving bases. The fish may of course have Il ritorno abituale verso un posto noto di un individuo di arrived in the bay a few days earlier than these reports Mycteroperca fusca è stato osservato in natura per un periodo but probably not more than one week earlier. di 25 anni. L’esemplare lascia la baia di Garajau sulla costa The fish can be recognized individually, not solely meridionale dell’isola di Madeira in primavera e vi fa ritorno because it is xanthistic (other xanthistic individuals ogni anno in autunno. Questo studio è la prima documen - tazione a lungo termine che dimostra il ritorno di un pesce of Mycteroperca fusca have been seen at Madeira nello stesso sito con cadenza annuale, secondo modalità si- Island and elsewhere), but by the pattern of white mili a quelle degli uccelli migratori. patches on its yellow body. A continuous photo - graphic record documents the gradual change in the INTRODUCTION size and shape of some of the white patches on the It has long been known that many marine fish animal (compare Figs 2 and 3); other patches, e.g. species migrate annually. Waschkewitz & Wirtz the one on the left pectoral fin, have remained con - (1990) provided the first record that – like a migra - stant in size and shape over the 25 years of obser - tory bird – an individual fish returned to the same vation. 31 aqua vol. 13 no. 1 - 25 October 2007 The return of the yellow grouper – annual migration and return to the same site by a xanthistic Mycteroperca fusca (Pisces: Serranidae) RESULTS Not all M. fusca in the bay migrate annually. Some The xanthistic M. fusca leaves the bay of Garajau in of them stay during the time the xanthistic individ - April-May each year. Departure dates cannot be ual is away. We do not know if those staying are the given precisely because in April the fish tends to dis - same every year (i.e. not migrating at all) or different appear for a few days as if it had started to migrate individuals during different years (i.e. migrating but but then to reappear again. We do not know where at intervals greater than one year). the fish migrates to but the direction appears to be Discussion : I have now extended the study of to the east. It has repeatedly been seen in a bay about Waschkewitz & Wirtz (1990) to a time span of 25 3 km to the east of Cape Garajau. years, giving the first long-term record of a fish hom - The dates of the first re-sighting of the xanthistic ing to the same site annually. The only comparable Mycteroperca fusca in the bay of Garajau each year study appears to be that of Domeier & Nasby-Lucas from 1981 to 1988 were, respectively: 19 Sept., 17 (2007) who reported annual re-sightings of photo - Sept., 5 Oct., 6 Oct., 22 Oct., 7 Oct., 19 Oct. and graphically identified white sharks at Guadalupe 25 Sept. Island, Mexico, where these animals aggregate annu - In 1989, 1990 and 1991, the dates of first re-sight - ally in autumn and winter; five males were seen in ing were not recorded but the fish in these years left each of the five study years. in spring and arrived in autumn, as previously. From The advantage of photographic identification is 1992 to 1997 the xanthistic Mycteroperca did not that animals need not be tagged (capture and/or the appear in the bay of Garajau and was presumed tag might change their behavioural pattern) and low dead. On 8 September 1998 the yellow grouper expense is incurred. On the other hand, tagging, in reappeared and has since continued its annual particular with electronic data storage, provides data migration and return to the same site. Between from a much larger area and allows migration to be 1998 and 2006 the dates of the first sighting were: 8 followed over larger distances. Hunter et al. (2005) September 1998, 19 November 1999, 13 March were able to reconstruct seasonal migration of an 2000, 20 October 2001, 13 October 2002, 30 individual thornback ray (Raja clavata) tagged with August 2003, 4 October 2004, 14 September 2005 an electronic storage tag; the tag recorded 423 days and 12 October 2006. When returning in autumn, of data, which indicated migration from the Thames the fish was noticeably “skinny”. Shortly before leav - estuary to the central southern North Sea in winter ing it appears well fed. and a return to the Thames estuary area the follow - In 1988, R. Waschkwitz estimated the length of ing spawning season. the fish at about 80 cm (Waschkewitz & Wirtz Shapiro (1987) and Coleman et al. (1996) have 1990). Nineteen years later, I now estimate the reviewed the reproductive behaviour of groupers. length of the fish at about 90 cm. Most carefully studied groupers are protogynous Fig. 1. The normal colour pattern of Mycteroperca fusca . Photo taken in the bay of Garajau, Madeira Island by P. Wirtz. aqua vol. 13 no. 1 - 25 October 2007 32 Peter Wirtz hermaphrodites. Spawning is usually restricted to tive patterns of other grouper species and the obser - particular moon phases of one to three successive vation that the animal is well fed when leaving but months. Many grouper species are known to aggre - thin when returning suggest that the xanthistic M. gate for spawning at what seem to be traditional sites fusca leaves the bay of Garajau in spring to migrate to (e.g. van Sant et al. 1994, Sadovy et al. 1994, a still unknown spawning site. We do not know why Domeier & Colin 1997). Tagged Epinephelus striatus the fish stays away for half a year, i.e. much longer migrated up to 240 km to spawning aggregations than the likely spawning period. (Carter et al. 1994). Comparison with the reproduc - Why does the yellow grouper return to the same Fig. 2. The xanthistic individual from the bay of Garajau in the year 2003. Photo by P. Wirtz. Fig. 3. The xanthistic individual from the bay of Garajau in the year 2005. Photo by P. Wirtz. 33 aqua vol. 13 no. 1 - 25 October 2007 The return of the yellow grouper – annual migration and return to the same site by a xanthistic Mycteroperca fusca (Pisces: Serranidae) place every year? Possible advantages of site fidelity Reproductive styles of shallow-water groupers (Pisces: are a “prior residency” effect leading to easier acquisi - Serranidae) in the eastern Gulf of Mexico and the conse - tion of a territory and a hunting advantage in a well- quences of fishing. Environmental Biology of Fishes 47: known environment (see Hoffman et al. 2006 and 129-141. CRABTREE , R. E.