1. BIOLOGY AND POPULATION DYNAMICS OF LOLIGO VULGARIS IN CATALAN WATERS (NW MEDITERRANEAN)
P. Sanchez1, M. Baeta2 and R. Allue3
1 Institut de Ciencies del Mar-CSIC, Barcelona Spain.
2 ECOPROGES,S.L, Barcelona Spain.
3 DARP, Generalitat de Catalunya, Barcelona Spain.
Material and methods
Sampling was carried out on board commercial trawlers on a monthly basis, from October 2003 to December 2005 in the Catalan coast (NW Mediterranean). Specimens were sexed and dissected in the laboratory, recording ML, total wet weight (BW) and the gonad weight (GW). Characteristics of egg masses, batimetry, substrate where they were fixed, were registered during one year around the Catalan Coast.
Mediterranean Sea
Minimum sizes (2 cm ML) of L. vulgaris show up from October to December and maximum sizes from November to February.
Males were more precocious than females. The smallest mature male was 14 cm ML and the smallest female measure 16 cm ML.
Mature females were present throughout the year, but a strong peak of maturation was observed in February.
The allometry coefficient b is higher in females (2.49) than in males (2.41). In both sexes growth is not isometric and weight increases relatively slower than length.
Period with biggest proportion of recruits (<10 cm) were from August to November.
Egg-masses were found throughout the year.
Discussion
The result on the maturity process of Loligo vulgaris obtained in the present study are similar to those found by Mangold-Wirz (1963) in Western Mediterranean and Guerra & Rocha (1994) in the Atlantic. The species spawns through the year with main peak in February and secondary peaks in June and August. Egg mass was also found all over the year. The results on spawning season is also in agreement with the presence of recruits all month with main peaks in October and secondary peaks in March and August.
References
Mangold-Wirz K., Biologie des Cephalopodes benthiques et nectoniques de la Mer Catalane. Vie Millieu, Supl. 13, 285pp.
Guerra, A & Rocha, F. (1994) The life history of Loligo vulgaris and L. forbesi (Cephalopoda: Loliginidae) in Galician waters (NW Spain) Fisheries Research, 21, (1-2):