Guerra, Á., Roura, Á., González, Á. F., Pascual, S., Cherel, Y., and Pérez-Losada, M. 2010. Morphological and genetic evidence that Octopus vulgaris Cuvier, 1797 inhabits Amsterdam and Saint Paul Islands (southern Indian Ocean). – ICES Journal of Marine Science, 67: 1401–1407.

Guerra, Á., Rodríguez-Navarro, A. B., González, Á. F., Romanek, C. S., Álvarez-Lloret, P., and Pierce, G. J. 2010. Life-history traits of the giant squid Architeuthis dux revealed from stable isotope signatures recorded in beaks. – ICES Journal of Marine Science, 67: 1425–1431.

This study aimed to determine the spawning strategy in the Atlantic bobtail squid Sepiola atlantica, in order to add new information to the knowledge of its reproductive strategy. A total of 12 females that spawned in aquaria were examined. Characteristics of the reproductive traits and egg clutches were similar to those of other known Sepiolidae. Clutch size varied from 31 up to 115 eggs. Females of this species had incorporated up to 1.58 times of their body weight into laid eggs. The size of laid eggs showed a positive correlation with maternal body size, supporting the idea that female size is a determinant of egg size. Our data suggest that S. atlantica is an intermittent terminal spawner, and that its spawning strategy comprises group-synchronous ovary maturation, multiple egg laying, and deposition of egg clutches in different locations. The obtained data provide insights for future comparative studies on reproductive allocation.

Four visual censuses targeting Octopus vulgaris living in dens on sandy bottoms were carried out from June to October 2013 in the National Park of the Atlantic Galician Islands (NW Spain). Censuses were undertaken by scuba diving between 5 and 21 m depth in daytime. The total area swept was 13.75 ha. There were no significant differences between octopus presence in dens during open and closed fishing seasons. Depth had a significant negative relationship with occupancy. The average number of dens per 1000 m2 was 3.84±0.84 in June and 3.89 in October. The area per den was 260 m2. Den number estimations varied between 1586 and 2057. The largest number of dens (76.5%) was found between 5 and 10 m depth. Den distribution was clumped. No significant differences were found between octopus size classes (small, medium and large) and den diameter. Associate dens were observed. There were no significant differences in den diameter and shell types found around the middens. Many dens could be “permanent”. Drilling bivalve shell behaviour is discussed. The surveyed area had around 1100 individuals, mainly small specimens. No significant differences were found between octopus size and depth. Substrate, den type and food abundance and availability (especially razors Ensis arcuatus) seem to be the main factors influencing dens and octopus density and distribution. Den availability does not appear to be a limiting factor in this case. Temperature, den availability, predators and fishing pressure influencing density and distribution are discussed. Rodas inlet may be a preferential habitat for O. vulgaris individuals ranging from 200 to 2000 g, but especially small specimens ( ≤ 1000 g).

11 páginas, 5 figuras, 5 tablasWe evaluated specific habitat features (bottom substrate type, depth, temperature, season and latitude-longitude) at random locations in the Cíes Islands (Galician Atlantic Islands National Park, Northwest Spain) to determine their impact on Sepia officinalis spawning habitat use. We performed underwater visual transects via scuba diving. In total, 94 transects were conducted between April 30, 2012 and July 17, 2015. Habitat features were evaluated as predictors of the presence/absence of egg clusters using Generalised Additive Models. Statistical analyses revealed the following: (a) the probability of finding eggs was significantly higher on hard bottom substrate type containing sea fans and sea tube worms; (b) the sectors where the egg presence was highest were the most shelters zones of Bajo de Viños and Piedra del Borrón, two hard bottom shoals covered by sea fans and sea worms and located in the central Cíes Islands or Faro Island; (c) The preferential depth ranged from 8 to 13 m; (d) as temperatures rose, the probability of finding eggs decreased, which was a sign of the seasonality of the spawning event of the species; and (e) eggs were most common in the winter. A total of 18 additional non-random underwater visual transects were then performed in the Viños and Borrón shoals between December 10, 2014 and August 20, 2015. We calculated the number of egg clusters found in two fenced areas (0.04 ha) located in Viños and Borrón, which showed that Viños was a most suitable spawning habitat than Borrón. The number of eggs per cluster varied from 4 to 82. The spawning period for this species lasted from the beginning of December until the end of June, when bottom temperature ranged from 12.5 °C to 14.75 °C. These microhabitat data reveal indicators of common cuttlefish spawning habitat utilisation and should help identify targets for habitat improvement projects and ecosystem management approaches within this national park and elsewhereM. Sestelo’s research was supported by research grant SFRH/BPD/93928/2013 of “Fundação para a Ciência e a Tecnologia” (FCT) and by FEDER Funds through “Programa Operacional Factores de Competitividade—COMPETE” and by Portuguese Funds through FCT, in the form of grant PEst-OE/MAT/UI0013/2014. Project financial support was provided by the Organismo Autónomo de Parques Naturales de España of the Ministerio de Agricultura, Alimentación y Medio Ambiente (CEFAPARQUES, Project number: 458/2011)Peer reviewe