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Presence of 1 year‐old dusky groupers along the French Mediterranean coast

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Journal of Fish Biology
Authors:
Pascaline Bodilis at Université Côte d'Azur
Pascaline Bodilis
A. Ganteaume
A. Ganteaume
A. Ganteaume
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Patrice Francour at University of Nice Sophia Antipolis
Patrice Francour
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Abstract

One year-old dusky groupers Epinephelus marginatus have been recently and regularly observed in different areas along the French Mediterranean coast.
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Presence of 1year-old dusky groupers along the French
Mediterranean coast
P. B ODILIS*, A. GANTEAUME†AND P. F RANCOUR*‡
*Laboratoire Environneme nt Marin Littoral, Universite
¤de Nice-Sophia Antipolis, Parc
Valrose, 06108 Nice Cedex 02, France a nd †Atelier Bleu du Cap de l’Aigle, Parc du Mugel,
136 00 La Ciotat, France
(Received 17 July 2002, Accepted 14 November 2002)
One year-old dusky groupers Epi nephelus marginatus have been recently and regularlyobserved in
different areas along the French Mediterranean coast. #2003 Th e Fisheries So cietyof the British Isles
Key words: Epinephelus; grouper; Mediterranean; recru itment.
Since 1986 the number of observations of the dusky grouper Epinephelus margina-
tus (Lowe) along the French coast of the north-western Mediterranean Sea has
steadily increased. Moreover, a change has been observed recently with a propor-
tional increase of dusky groupers <40 cm total length (L
T
) (Francour & Finelli,
1991).
At the end of the 1980s, dusky groupers of 30^40 cm L
T
were observed along
the coast of the Department of Var, particularly in the Port-Cros National Park
(Francour & Harmelin, 1988) and in the natural reserve of Scandola (Corsica)
(Miniconi et al., 1990; Francour & Finelli,1991). Since 1990, groupers of10 cm L
T
have
been reported in Corsica and along the coast of theVar (Lelong, 1993). A review of
published and unpublished data was initiated by Francour & Ganteaume (1999)
who analysed c. 150 dusky grouper (40 cm L
T
) observations. This has been
substantially improved in the present study with a review of c. 300 young dusky
grouper observations. Several hypothezes highlighted in the study of Francour &
Ganteaume (1999) were re-analysed and the recruitment of E. marginatus was
characterized by addressing the following questions: Is the arrival of small
groupers (<10 cm L
T
) along the Mediterranean French coast regular or not? Can
a hypothesis be proposed to explain these new observations?
Observations of dusky groupers (40 cm L
T
) were carried out by the mem-
bers of the GEM (Groupe d’Etude du Me
¤rou: http://www.aquanaute.com/gem)
or by other scientists. In addition information was supplied by SCUBA and free
divers with the help and support of the Biology Committee of the French
Federation of Underwater Studies and Sports and different SCUBA diving clubs.
‡Author to whom correspondence should be addressed. Tel.: þ33 4 92 0 76 832; fa x : þ33 492076849 ; email :
francour@unice.fr
Journal of Fish Biology (20 03) 62, 242^246
doi:10.1046/j.0022-1112.2003.00028.x, available online at http://www.blackwell-synergy.com
242
#2003 The Fisheries Soc iety of the Br itish Isles
The smallest individuals (25 cm L
T
) were more frequently observed in shallow
(0^25 m) water. Several individuals, however, between 20 and 25 cm were observed
at a depth of 30 m. The largest individuals (25 <L
T
40 cm) were regularly
observed at lower depths from 15 m to as d eep as 6 0 m. A ll siz e groups were p resent
in shallow waters (0^15 m depth).
Very small dusky groupers (2^3 cm), 1month old, recruits from spawning in
August (Marino et al., 2001), were only observed during a short period of time
(September to October). Individuals belonging to the size class 5^10 cm have been
observed earlier, June in a few cases, but normally from July to August. These
larger fish were probably recruited the previous yearand so were10^12 months old.
Even if information on dusky groupers along the Mediterranean coasts outside
France is fragmentary and uncomplete, the presence of small groupers (20 cm
L
T
) may be a normal and regular phenomenon in the south of Spain (J. Mas, pers.
comm.) and along the North African coasts (C. Chauvet, R. Semroud & D. Soltan,
pers. comm.). In Sardinia, the observation of small individuals of E. marginatus
(15^20 cm) was exceptional until 1989 (Russino et al., 1991). For the south of Italy
and the Adriatic Sea (Croatia), the presence of small dusky groupers (25 cm L
T
)
was reported recently, but little information was collected to descr ibe the status of the
assemblages of E. margi natus in these areas (S. Bussotti & P. Guidetti, pers. comm.).
The measured or estimated maximum and minimum sizes of dusky groupers
observed between 1986 and 20 01 are shown in Table I. The first g roupers <10 cm L
T
were observed in 1989 in Cerbe
're-Banyuls (only one individual) and in the south
of Corsica (several observations) (Fig.1). Many small dusky groupers were
observed in Corsica (north and south) between 1990 and 1992, in 1996 and 2001.
In 1992^1993, several observations were reported along the coast of theVar: mainly
in the Port-Cros National Park and in Les Embiez Island. During 1996^1997,
observations of small dusky groupers were made in Monaco and the Port-Cros
National Park. In 1999, other observations of small dusky groupers were reported
in the Co
“te Bleue Marine Park and in 2001 in the Port-Cros National Park and in
the south of Corsica.
In Corsica and Sardinia, recruitment may have occurred in1990 and 1991 and each
year from 1995 till 2001 (except perhaps in 1997). For this area, data for 1991^1994
are missing. For the French coast (Corsica excluded) recruitment may have
occurred in 1991, 1992, 1994 and each year since 1996. The observations of dusky
groupers collected for the year 2002 were not sufficient to make conclusions about
recruitment in 2001. In a few cases the very small size of the observed individuals
(<5cm L
T
) suggests that spawning occurred near the site of observation. In the
other cases recruitment was assumed after observations of 1 year-old groupers the
following year. These spawning areas correspond with suppositions made by
Louisy & Culioli (1999) about the known or suspected reproductive sites of the
dusky grouper in the north-western Mediterranean Sea: Corsica (Revellata,
Lavezzi Islands), Var (Les Embiez, National Park of Port-Cros), Pyre
¤ne
¤es-
Orientales coasts (the Marine Reserve of Cerbe
're-Banyuls) and Spain (the Medes
Islands) (Fig. 1).
Several factors maybe responsible for the regular recruitment on the French coast
since 1995: (1) a possible modification of the sex ratio caused by the settlement of
small size dusky groupers, that now gives an advantage to females (youngdusky group-
ers, i.e. females were absent from the French coast b efore 1990, Chauvet & Francour,
DUSKY GROUPERS I N THE MEDI TERRANEAN 243
#2003 The Fisheries Soci ety of the Br itish Isles, Journal of Fish Biology 20 03,62, 242^246
TABLE I. Summary of the length ranges observed of Epinephelus marginatus <40 cm L
T
, on the French Mediterranean coast. The information
is classified by areas (see Fig. 1), from the south to the north, then from the east to the west, i.e. in the direction of the Liguro-Provenc¸al current.
Places and years yielding several observations of small individuals ( L
T
<10 cm) are in bold
Year
South
Corsica
North
Corsica Ligurie
Monaco
Cannes Cavalaire Port-Cros Giens Toulon Embiez
Co
“te
Bleue
Golfe du
Lion
Cerbe
're-
Banyuls
1986^87 30^40
1988 7^7 40^40 40^40 44^44
1989 8^8 40^40 30^40 5^10
1990 7^16 7^40 8^40 20^30
1991 5^17 30^40 30^40 4^4 20^30
1992 10^25 15^15 30^40 20^40 30^40 2^40 40^42 20^30 15^40
1993 20^20 20^35 10^40 10^10 11^13 36^40 25^40
1994 30^40 30^40 22^22 30^40
1995 30^40 30^40 30^40 5^40 30^40
1996 15^15 5^10 15^20 30^40 5^40
1997 5^10 30^40 15^30 10^35 20^30 10^40 20^40 25^40 35^35
1998 15^15 35^40 15^20 15^40 3^40 25^35 5^35 15^15 10^17
1999 75^75 8^8 25^25 15^45 15^15 5^40 7×5^40 16^16
2000 75^15 15^40 75^15 8^8 15^15 25^25
2001 5^15 15^30 7×5^25 17^17
244 P. B O D I L I S ET AL.
#2003 The Fisheries Soc iety of the Br itish Isles, Journal of Fish Biology 2003,62, 242^246
1990); (2) the partial protection of the species brought by a moratorium (19 93^2002);
(3) the warming of the waters ofthe Mediterranean Sea (Francour etal.,1994).
Despite these changes, the long life-span of E. marginatus (>30 years) and the
age of sex change (between 10 and 15 years) make the impact of young dusky group-
ers on present adult populations limited. In addition, a possible removal of the
legal protection of dusky groupers in France in January 2003 and a resumption of
spearfishing could have an adverse impact on populations.
References
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Francour, P. & Harmelin, J. G. (1988). Inventaire de la faune ichtyologique marine de
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Francour, P. & Finelli, F. (1991). Comple
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FIG.1. Map of the main known or suspected reproductive sites of the dusky grouper in the north-western
Mediterranean Sea (modified from Louisy & Culioli, 1999). *, possible reproduction activity; 6,
observed reproduction activity; , observed spawning. Upper case letters, marine protected areas.
DUSKY GROUPERS I N THE MEDI TERRANEAN 245
#2003 The Fisheries Soci ety of the Br itish Isles, Journal of Fish Biology 20 03,62, 242^246
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Marine Life 9, 47^57.
Marino, G., Azzurro, E., Massari, A., Finoia, M. G. & Mandich, A. (2001). Reproduction
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Miniconi, R., Francour, P. & Bianconi, C. H. (1990). Inventaire de la faune ichtyologique
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Russino, G. A., Chessa, L. A., Russo, G. F. & Mazzella, L. (1991). New record of Epine-
phelus spp. (Osteichthyes, Serranidae), on the coast of Alghero (N. W. Sardinia ^
Italia). In Les Espe
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246 P. B O D I L I S ET AL.
#2003 The Fisheries Soc iety of the Br itish Isles, Journal of Fish Biology 2003,62, 242^246
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  • Apr 2018
La perte d'habitat engendrée par l'artificialisation des côtes a de graves conséquences sur la biodiversité marine. Aussi, dans une optique de maintien de la biodiversité et des stocks de poissons, il peut s’avérer intéressant de restaurer certaines fonctions écologiques dans les zones anthropisées. Cette thèse avait pour objectif d’estimer le rôle potentiel des ports en tant qu’habitat pour les juvéniles de poissons côtiers et d’évaluer dans quelle mesure ce rôle peut être amélioré par le biais d’actions de restauration. Des expérimentations en aquarium ont permis d’estimer que le taux de survie des juvéniles sur des habitats artificiels utilisés à des fins de restauration était comparable à celui observé sur des roches. Une étude de la distribution spatiale des juvéniles à l’échelle d’un paysage sous-marin a ensuite montré que les ports pouvaient abriter des densités en juvéniles représentant de 50 à 90 % de celles retrouvées en milieu naturel. Les densités à l'intérieur des ports étaient cependant tributaires du type d’habitat considéré; les quais sans complexité structurale abritant les densités les plus faibles. Enfin, l'étude de cas concrets, a montré que la réhabilitation des ports pouvait significativement augmenter les densités de juvéniles à l’échelle de l’habitat, celles-ci pouvant atteindre des niveaux comparables au milieu naturel. Toutefois, ces bénéfices restaient faibles à l’échelle d’un port dans sa globalité. Ces travaux suggèrent un réel potentiel des infrastructures portuaires en tant qu’habitat juvénile alternatif, en particulier si des actions de restauration y sont entreprises. Cependant, pour plus d’efficacité, les projets de restauration devraient être menés à large échelle et utiliser une diversité d’habitats artificiels. La restauration écologique des ports peut ainsi être employée comme un outil complémentaire aux mesures de protection dans le cadre d’une gestion intégrée des zones côtières à l’échelle du paysage.
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Are the Mediterranean waters becoming warmer? Information from biological indicators
Article
Full-text available
  • Sep 1994
  • MAR POLLUT BULL
The authors are biologists specializing in benthos or ichthyofauna survey. They have worked in marine protected areas or in other littoral zones of the Mediterranean Sea for a long time. The use of SCUBA diving as a sampling method allows them a great knowledge of the benthos and ichthyofauna. Charles-Francois Boudouresque is vice-chairman of the Benthos Committee of the CIESM, and chairman of the scientific committees of the National Park of Port-Cros and of the Natural Regional Park of Corsica (marine reserve of Scandola). The other authors are members of these scientific committees.
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Reproduction in the dusky grouper from the southern Mediterranean
Article
Full-text available
  • Apr 2001
Demographic data and gonad histology confirmed that the dusky grouper Epinephelus marginatus is a protogynous hermaphrodite that follows a monandric pathway to sexual development. Females reached first sexual maturity at 36·7 cm L S and estimated mean length at first maturity (L 50) was 43·8 cm L S for females and 81·3 cm L S for males. Adult sex ratios during the reproductive period were c. 3·5 : 1 females to males. Females exhibited group-synchronous ovarian development and multiple ovulation occurred over the spawning period. Gonads were ripe from early May and spawning occurred from June until early September. The size of ripe testes (0·6% W) indicated strong oligospermy and suggested a mating system with no sperm competition. Sexual transition was protogynous involving regression of ovarian tissue and proliferation of testicular tissue in the gonads. Transitional individuals occurred from May through November and accounted for 9% of sampled adult population. Sex change occurred in fish 69–93 cm (L S) long and the size distributions of males and females overlapped over 27% of the L S range. Special zones were recognized as gathering areas for sexually mature dusky groupers during the reproductive period. 2001 The Fisheries Society of the British Isles
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PRESENCE DE JUVENILES DU MEROU BRUN (EPINEPHELUS GUAZA) SUR LE LITTORAL MEDITERRANEEN FRANÇAIS
Article
RESUME La rencontre avec le mérou brun (Epinephelus guaza) a toujours été recherchée par le plongeur et le chasseur sous-marin. Toutes les observations faites jusqu'à ces dernières années montraient l'absence totale d'individus pesant moins d'un kilo sur notre littoral. Pour les scientifiques, le mérou brun se reproduisait en Méditerranée méridionale (au Sud de la latitude 41.5° N) et une partie de la population se déplaçait par migrations successives pour atteindre nos côtes plusieurs années après. La découverte d'individus de quelques centaines de grammes depuis quatre ans puis de quelques grammes en automne 1991, semble indiquer que cette hypothèse n'est plus valable actuellement. Il est probable que sous l'influence de légères modifications climatiques, les aires de reproduction d'Epinephelus guaza se soient étendues plus au Nord en Méditerranée occidentale, comme c'est le cas pour d'autres espèces (Thalassoma pavo par exemple). 237 ABSTRACT An encounter with the brown grouper has always been a bonus for the diver or the spear-diver. Up to the last few years, all observations made on our shores confirmed the absence of individuals weighing less than a kilo. As far as the scientists were concerned, the reproduction of the brown grouper took place in southern Mediterranean, from where part of the population moved by successive migrations and reached our shores several years later. The discovery, in the last four years, of individuals weighing a few hundred grams and, in Automn 1991, of others weighing a few grams, seems to indicate this theory is no longer valid. It is probable that, due to the influence of slight climatic changes, the areas of reproduction of Epinephelus guaza have spread further North in the Mediterranean, as is the case for other species (Thalassoma pavo for instance).
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New record of Epinephelus spp
  • Jan 1991
  • G A Russino
  • L A Chessa
  • G F Russo
  • L Mazzella
Russino, G. A., Chessa, L. A., Russo, G. F. & Mazzella, L. (1991). New record of Epinephelus spp. (Osteichthyes, Serranidae), on the coast of Alghero (N. W. SardiniaÎ talia). In Les Espe' ces a' Prote¤ ger en Me¤ diterrane¤ e. (Boudouresque, C. F., Avon, M. & Gravez,V., eds), pp. 291^298. Marseille: GIS Posidonie.
Inventaire de la faune ichtyologique marine de Port-Cros. Scientific Report of Port-Cros National Park 14
  • Jan 1988
  • 65-79
  • P Francour
  • J G Harmelin
Francour, P. & Harmelin, J. G. (1988). Inventaire de la faune ichtyologique marine de Port-Cros. Scientific Report of Port-Cros National Park 14, 65^79.
Upper case letters, marine protected areas Synthe' se des observations sur l'activite¤ reproductrice du me¤ rou brun Epinephelus marginatus (Lowe, 1834) en Me¤ diterrane¤ e nord-occidentale Reproduction in the dusky grouper from the southern Mediterranean
  • Jan 1999
  • Du Sky G Rou P E R S I N T H E M E Di T E R R A N E A N Louisy
  • P Culioli
  • J M Marino
  • G Azzurro
  • E Massari
  • A Finoia
  • M G Mandich
*, possible reproduction activity; 6, observed reproduction activity;, observed spawning. Upper case letters, marine protected areas. DU SKY G ROU P E R S I N T H E M E DI T E R R A N E A N Louisy, P. & Culioli, J. M. (1999). Synthe' se des observations sur l'activite¤ reproductrice du me¤ rou brun Epinephelus marginatus (Lowe, 1834) en Me¤ diterrane¤ e nord-occidentale. Marine Life 9, 47^57. Marino, G., Azzurro, E., Massari, A., Finoia, M. G. & Mandich, A. (2001). Reproduction in the dusky grouper from the southern Mediterranean. Journal of Fish Biology 58, 909^927. doi: 10.1006/jfbi.2000.1502.
Pre¤ sence de juve¤ niles du me¤ rou brun (Epinephelus guaza) sur le littoral me¤ diterrane¤ en franç Marseille: GIS Posidonie. FIG.1. Map of the main known or suspected reproductive sites of the dusky grouper in the north-western Mediterranean Sea
  • Jan 1993
  • 237-242
  • P Lelong
Lelong, P. (1993). Pre¤ sence de juve¤ niles du me¤ rou brun (Epinephelus guaza) sur le littoral me¤ diterrane¤ en franç. In Qualite¤ du milieu marin ^ Indicateurs biologiques et physicochimiques (Boudouresque, C. F., Avon, M. & Pergent-Martini, C., eds), pp. 237^242. Marseille: GIS Posidonie. FIG.1. Map of the main known or suspected reproductive sites of the dusky grouper in the north-western Mediterranean Sea (modified from Louisy & Culioli, 1999).