Patterns of Investment in Reproductive and Somatic Tissues in the Loliginid Squid Loligo Forbesii and Loligo Vulgaris in Iberian and Azorean Waters

Hydrobiologia (2011) 670:201–221 DOI 10.1007/s10750-011-0666-8 ECOSYSTEMS AND SUSTAINABILITY Patterns of investment in reproductive and somatic tissues in the loliginid squid Loligo forbesii and Loligo vulgaris in Iberian and Azorean waters Jennifer M. Smith • Graham J. Pierce • Alain F. Zuur • Helen Martins • M. Clara Martins • Filipe Porteiro • Francisco Rocha Published online: 5 April 2011 Ó Springer Science+Business Media B.V. 2011 Abstract The veined squid, Loligo forbesii, is found fishery landings data from 1990 to 1992 and employs throughout the northeast Atlantic, including the waters additive modelling to examine the relationships off the Iberian Peninsula, and is a socio-economically amongst somatic growth, season and gonad growth, important cephalopod species, sustaining several in an attempt to determine the relative importance of small-scale commercial and local artisanal fisheries. intrinsic (e.g. nutritional state and body size) and This study uses Iberian and Azorean trawl survey and extrinsic (temperature and daylight) factors which contribute to maturation in L. forbesii. We compare the results with those from a comparative analysis of Guest editors: Graham J. Pierce, Vasilis D. Valavanis, contemporaneous data on Loligo vulgaris from the M. Begonã Santos & Julio M. Portela / Marine Ecosystems and Sustainability Iberian coast, and with a re-analysis of previously published results for L. forbesii in Scottish waters. J. M. Smith (&) Á G. J. Pierce Reproductive organ weight in both sexes of School of Biological Sciences (Zoology), University of L. forbesii from all ports shows seasonal patterns with Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK e-mail: [email protected] a fall/winter peak in maturation, as is expected with the animals’ year-long life cycle. Two maturity peaks G. J. Pierce (spring and winter) were found for both Azores Centro Oceanogra´fico de Vigo, Instituto Espanõl de L. forbesii males and females, possibly evidence of Oceanografıá, P.O. Box 1552, 36200 Vigo, Spain two breeding cohorts, with males maturing approxi- A. F. Zuur mately 1 month earlier than females in both seasons. Highland Statistics Ltd., 6 Laverock Road, Newburgh, For L. vulgaris, three annual peaks in reproductive Aberdeenshire AB41 6FN, UK weight were identified. With the exception of H. Martins Á F. Porteiro L. forbesii males from Scottish waters, in all study Departmento de Oceanografia e Pescas, Universidade dos animals, the partial effect of mantle length and mantle Açores, 9901-862 Horta, Portugal weight on reproductive weight is positive up to large body sizes. The relationship between nutritional status M. Clara Martins Sternaserv, Lda. Consultoria e Serviços Tećnicos, and reproductive weight is also generally positive. 1150-215 Lisbon, Portugal Geographic variation in the relationships, as seen between Scottish males and samples from the other F. Rocha study areas, is hypothesised to be largely attributable Departamento de Ecologıá y Biologıá Animal, Campus as Lagoas-Marcosende, Universidad de Vigo, to local differences in environmental conditions (pro- 36310 Vigo, Spain ductivity, food availability, temperature, upwelling), 123 202 Hydrobiologia (2011) 670:201–221 although differences between L. forbesii from the This article makes use of a data set collected Azores, Scotland and mainland Europe may also relate during a European collaborative project in the early to previously documented genetic differences. 1990s, when detailed biological data were collected over a 2-year period, to examine the intrinsic and Keywords Squid Á Life history Á Maturation Á extrinsic factors determining the timing of maturation Reproductive investment Á Somatic growth Á Iberian of the squid L. forbesii (Cephalopoda: Loliginidae) in Peninsula waters off of the Iberian Peninsula, the Azores, and Scotland, and includes a similar analysis of an additional loliginid squid, L. vulgaris, in an attempt to identify any differences in growth patterns between Introduction sexes and the two species, particularly in Iberian waters, where the species’ ranges overlap. Information on the timing of growth and maturation The distribution of L. forbesii includes coastal and on the factors which cause underlying variation waters of the northeast Atlantic from as far north as in reproductive processes is important to underpin the Faroe Islands to the upper west coast of Africa, as sustainable fishing. Fishery managers need to avoid well as the Azores and the Mediterranean (Roper both growth overfishing (i.e. loss of yield caused et al., 1984; Salman & Katag˘an, 2002). L. vulgaris by taking animals too early in the life cycle) and shares the southern part of this range (Guerra & recruitment overfishing (negatively impacting recruit- Rocha, 1994), being almost completely absent from ment by removing too many animals before they can Scottish waters (Pierce et al., 1994b, 1998) whilst spawn). In annual, seasonally breeding species such present throughout the Mediterranean (Guerra et al., as the squid Loligo forbesii, the timing of peak yield 1994). During the 1990s, catches of L. forbesii off from the fishery is necessarily linked to the timing of Iberia began to decline and, by the mid-2000s, it the life cycle (see Pierce et al., 1994a, b). appeared that the species was no longer prevalent The process of maturation is driven in part by across the southern part of its range (Chen et al., intrinsic factors such as age, size and nutritional 2006), although landings in northern areas have status, and extrinsic factors such as season, which increased in recent years [e.g. northeast Scotland affects length of daylight and water temperature. In during the years of 2003–2005 (ICES, 2008; authors’ the natural environment, these factors may very well unpublished data)], and it continues to be found in interact. For example, water temperature will influ- commercial and research catches in Spain and Portu- ence food availability, which will in turn affect gal. It was hypothesised that the decrease of L. forbesii nutritional status and growth rate. Favourable feeding in these areas, and in turn, the increase in abundance and temperature conditions after hatching have been in the northern area of the species’ distribution range, found to affect growth rates and the onset of may have been related to an increase in SST in maturation in Loligo vulgaris in Portuguese waters southern French and Portuguese waters after 1993 (Moreno et al., 2007), and Loligo forbesii from the (Chen et al., 2006). At the time when the present Azores exhibited temperature-sensitive growth rates samples were collected, the two Loligo species were when reared in laboratory conditions (Forsythe & sympatric along the coast of the Iberian Peninsula, Hanlon, 1989). In addition, it is also debated as to although results from research cruises suggested whether somatic tissues are remobilised to contribute that L. vulgaris tended to be found closer to the stored energy reserves to gonad growth. Although coast (Cunha et al., 1995; Hastie et al., 2009) than experimental laboratory studies and long time-series L. forbesii. As such, both as a mechanism to reduce of data would be most beneficial in revealing competition and/or due to genetic differences, it might responses of squid to both internal and external be expected that growth and maturation patterns of signals for the onset and time course of maturation, L. vulgaris would differ from those of L. forbesii. useful insights can still be extracted from cross- Rocha & Guerra (1999) found differences in both comparisons of biological data collected from market body size and statoliths size (as a percentage of mantle samples of different species and from across different length) between the two species in Galician waters, geographical regions. suggesting that their growth patterns may differ. 123 Hydrobiologia (2011) 670:201–221 203 In Galician waters, loliginid squid are caught both investment (body weight), nutritional status (diges- as a by-catch in commercial trawling and by artisanal tive gland weight), size (body length) and season in hand-jigging (Guerra & Rocha, 1994; Rocha & samples of L. forbesii and L. vulgaris, and compares Guerra, 1999). Males and females landed in this results with those found in squid from Scottish region have been shown to mature at two different waters. The data were previously used to describe the modal sizes, with males maturing earlier than females annual life cycles (Boyle & Pierce, 1994; Guerra & (Guerra & Rocha, 1994). Loligo fisheries in Portu- Rocha, 1994; Moreno et al., 1994; Porteiro & guese waters are mainly carried out by the commer- Martins, 1994) but there has been no previous cial trawl fishery, but also artisanally with hand jigs, attempt to investigate the links between maturation, with trawling gear accounting for the majority of the growth, nutritional state and season. As a result of the annual recorded catch (Cunha & Moreno, 1994). Two short time-series available, it is possible to look for different size groups at maturity in males and females differences in growth and maturation between years, of both L. forbesii and L. vulgaris have also been but not to ascribe them to specific differences in documented amongst Portuguese samples (Coelho environmental conditions. It is hypothesised that et al., 1994; Moreno et al., 1994), with males differences between regions and species might arise maturing at a smaller size than females for due to the plasticity of the life cycle biology in L. vulgaris

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