The life history of Loligo vulgaris and Loligo forbesi (Cephalopoda: Loliginidae) in Galician waters (NW Spain)

Abstract

The population biology of Loligo vulgaris and Loligo forbesi in Galician waters is described based on monthly samples from the fishery obtained during the period February 1991-June 1992. Maturity was assessed using a maturity scale and indices.The estimated number of oocytes in mature females varied from 782 to 21 885 in L. vulgaris and from 1317 to 14 956 in L. forbesi, and showed a slight positive correlation with the length of the mantle (ML) for both species. Oocytes in the ovaries fall into three discrete size classes, which suggests that L. vulgaris and L. forbesi are intermittent or multiple spawning species. In L. vulgaris males mature at two different modal sizes, hence perhaps at two different ages, while in L. forbesi this occurs in both males and females. Males mature earlier in the season than females in both species. The maximum number of spermatophores found was 1010 and 1000 in two L. vulgaris males with 119 mm and 400 mm ML respectively, and 1035 in a L. forbesi male with 150 mm ML. In both species, spermatophore length increases with ML. Loligo forbesi males maturing at a larger size produce fewer but larger spermatophores than those maturing at a small size. Loligo vulgaris spawn throughout the year, but the period of more intensive spawning extends from December to April. The breeding season of L. forbesi extends from December to May, the more intensive spawning extending from December to February. Sex ratios were variable for both species. Age and growth for both species and sexes were estimated by examining growth increments in the statoliths. Like-sized individuals had different ages in both species. The life span of L. vulgaris was estimated at about l year while L. forbesi seems to reach an age of 15-16 months. A list of prey species found in gastric contents of both species is given. The diet of L. vulgaris comprises fish (86.8%), cephalopods (6.0%), crustaceans (3.0%) and polychaetes (1.8%), and the diet of L. forbesi includes fish (75.6%), crustaceans (18.5%) and cephalopods (4.4%).

Patrones espaciales y temporales en talla y maduración de <i>Loligo plei</i> y <i>Loligo sanpaulensis </i>(Cephalopoda: Loliginidae) en aguas del sureste de Brasil, entre 23°S y 27°S.

“…The variation range of mean GSI values was narrow for L. sanpaulensis and for males of L. plei, but seems to be comparable with other studies (i.e. see ΔIGS in Guerra and Rocha (1994) for L. vulgaris and L. forbesi; Perez et al (2002) for L. plei, and Olyott et al (2006) …”

Reproductive activity of the tropical arrow squid Doryteuthis plei around São Sebastião Island (SE Brazil) based on a 10-year fisheries monitoring

“…In males, the GAMLSS suggested the co-occurrence of two different groups, one that matures at 187 mm ML and another that matures at 290 mm ML. This kind of pattern among males seems to have been observed in Loligo vulgaris caught off southern Portuguese waters (Coelho et al, 1994), L. vulgaris and L. forbesi males in Galician waters (Guerra and Rocha, 1994) and D. plei caught by the industrial trawling off Brazil (Marques and Gasalla, 2002;Perez et al, 2002). Hanlon (1998) and Hanlon et al (2002) studying the behavior of Loligo sp.…”

“…Previous studies on the reproductive activity of D. plei in Brazil have described spatial and seasonal patterns of maturity by using the gonado-somatic index (GSI) Rodrigues and Gasalla, 2008), as has been occurring for other loliginids around the world (e.g., Loligo vulgaris reynaudii in South Africa, Olyott et al, 2006; Loligo forbesi in European waters, Porteiro and Martins, 1994;Guerra and Rocha, 1994;Rocha and Guerra, 1999;Pierce et al, 1994;Coelho et al, 1994;Pham et al, 2009; and Doryteuthis sibogae off the southeast coast of India, Neethiselvan et al, 2001). However, more recently, some generalized additive models (GAMs), based on the gonad weight, have been proposed to better understand the reproductive activity of certain European loliginid's stocks (e.g.…”

Fecundity of the squid Loligo vulgaris, Lamarck, 1798 (Myopsida, Loliginidae) off northwest Africa

“…More recent attempts to assess total oocyte numbers have produced estimates ranging between 782-42,446 (Baddyr, 1988;Guerra and Rocha, 1994;Coelho et al, 1994). These estimates were based on the assumption that spawning is intermittent, as with many other squid species (Guerra and Rocha, 1994), and that the number of ripe eggs in the oviducts is much less than actual fecundity.…”

“…These estimates were based on the assumption that spawning is intermittent, as with many other squid species (Guerra and Rocha, 1994), and that the number of ripe eggs in the oviducts is much less than actual fecundity. However only yolk oocytes were counted.…”