Rapp. Comm. int. Mer Médit., 36,2001
329
Introduction
The blue-mouth, Helicolenus dactylopterus(Delaroche, 1809), is a
benthic species which inhabits the seabed at between 200 and 1000 m
depth (1). It is widely distributed in the eastern Atlantic, from the
Norwegian coasts to the south-west coast of Africa (2). In the
Mediterranean, blue-mouth is found along the continental shelf edge
and slope, where it is caught as by catch species of the bottom trawl,
long line and gill net fishery (3).
Material and methods
Samples of blue-mouth were collected on a monthly basis with a
hired commercial bottom-trawler in the East Ionian Sea (West Coast
of Greece) during July 1999 to June 2000. The depths of the sampling
stations ranged from 300-750 m. A total of 1229 specimens were col-
lected (462 males and 767 females). The maturity stage was deter-
mined using the gross sexual classification scale of Nikolsky (4).
Spawning period was determined from the analysis of the monthly
evolution of both the percentages of mature individuals and the mean
gonadosomatic index (GSI) throughout the sampling period. All indi-
viduals classified as stages I to II were considered to be sexually
immature, stage III as pre-spawning and those classified as stages IV
to VI were considered to be sexually mature. The volumetric method
(5) was used for the study of the fecundity. Overall, 22 gravid gonads
were examined. Oocytes were sized and counted. Hydrated and non
hydrated oocytes were counted and measured. Steel screens with
openings 1, 0.5 and 0,25 mm were used to separate the oocytes in size
ranges.
Results
The occurrence of gravid and spawning (stages IV-V) female blue-
mouth is predominant during winter months (January-March), indicat-
ing the spawning time (Fig. 1). On the other hand, pre-spawning
females were found from November to July.The GSI of the females
was high during winter months (Fig. 2). In December there is an
increase that peaks in February (1.27). It thereafter decreases slightly
in March, and in June approaches again the low values (0.19) similar
to the rest of the year.
Figure 1. Monthly percentages of immature (I-II), pre-spawning
(III) and spawning (IV-V) of female blue-mouth.
Ovaries contained a pronounced bimodal distribution of oocyte
diameters ranging from 0.22 to 0.64 mm and from 0.70 to 1.24 mm
(Fig. 4). The mean diameter of hydrated oocytes was found to be 0.834
mm.Total fecundity felt into the range 330639-9559 oocytes while
batch fecundity ranged from 22630-91 oocytes.
Figure 2. Annual cycle of the gonadosomatic index (mean +/-
SD) of female blue-mouth.
Figure 3. Diameter distribution of the oocytes.
Conclusion
The seasonal patterns of the percentage of mature blue-mouth (stage
IV and V) and the mean GSI, indicate the existence of a short repro-
ductive period, which extends from December to March. From the pre-
liminary results of the fecundity it can be said that this species exhibits
group-synchronous oocyte development.
References
1. Whitehead, P.J.P., Bauchot, M.L., Mureau, J.C., Nielsen, J. and
Tortonese, E., 1986. Fishes of the north-eastern Atlantic and the
Mediterranean. UNESCO, Paris.
2. Hureau, J.C. and Litvinenko, N.I., 1986. Scorpaenidae. pp. 1211-1229.
In:Whitehead, P.J.P., Baushot, M.L., Hureau, J.C., Nielsen, J., Tortonese,
E. (Eds.), Fishes of the North-eastern Atlantic and the Mediterranean,
Vol. 3, UNESCO, Paris,
3. Bauchot, M. L., 1987. Scorpaenidae. pp. 1290-1300. In: Fischer,W.,
Bauchot, M.L., Schneider, M. (Eds.), Fiches FAO d’identification des
especes pur les besoins de la peche (revision 1). Méditerranée et mer
Noire. Zone de pêche, 37, Vol.2. FAO, Rome.
4. Nikolsky, G.V., 1963. The Ecology of Fishes. pp. 352. Academic
Press, London,
5. Humanson, G.L., 1979. Animal tissue techniques. . 560 pp. W.H.
Freeman and Co., San Francisco.
REPRODUCTIVE CYCLE AND FECUNDITY OF BLUE-MOUTH (HELICOLENUS DACTYLOPTERUS,
DELAROCHE, 1809) IN THE EASTERN MEDITERRANEAN (IONIAN SEA, GREECE)
AnnaTerrats* and George Petrakis
National Centre for Marine Research, Hellinikon, Greece - annate@ncmr.gr, gpetr@ncmr.gr
Abstract
In this work, preliminary results on the reproductive cycle and on the fecundity of Helicolenus dactyloperusare presented. The breeding
period of the species was found to occur from December to March in the Eastern Mediterranean. Total fecundity ranged from 330639-
9559 and batch fecundity ranged from 22630-91 oocytes. Ovaries contained a pronounced bimodal distribution of oocyte diameters,
ranging from 0.22 to 0.64 mm and from 0.7 to 1.24 mm, indicating that the blue-mouth exhibits group-synchronous oocyte development.
Keywords : Ionian Sea, reproduction, spawning, teleostei.
