Horizontal and vertical distribution of cephalopod paralarvae (PL) from the Mesoamerican Barrier Reef System (MBRS) in the Western Caribbean was studied during two oceanographic cruises in 2006 and 2007. A total of 1034 PL belonging to 12 families, 22 genera, 24 species, 5 morphotypes and a species complex were identified. Abralia redfieldi, Onychoteuthis banksii and Ornithoteuthis antillarum were the most abundant taxa. The taxonomic identification from these three species was corroborated with DNA barcoding (99.8–100% of similarity). Paralarvae of Octopus insularis were reported for the first time in the wild. Most PL occupied the Caribbean Surface Water mass in the 0–25 m depth stratum. Largest paralarval abundances were related to local oceanographic features favouring retention such as the Honduras Gyre and Cozumel eddy. No day-night differences were found in PL abundance, although Abralia redfieldi showed evidence of diel vertical migration. Distribution of PL in epipelagic waters of the MBRS was probably related to ontogenetic migration, hydrographic features of meso and subscale, and to the circulation regimes dominated by the Yucatan Current. The MBRS represents an important dispersion area for PL, potentially connecting a species-rich Caribbean community with the Gulf of Mexico and Florida waters.

Octopus mimus is the main octopus targeted by the small-scale fishery in the Eastern Pacific. Commercial catches of octopus from the Reserva de Producción Faunística Marino-Costera Puntilla de Santa Elena (REMACOPSE) Marine Protected Area in Ecuador were sampled from July to December 2013 in order to describe the reproduction and population structure of this octopus. The 4171 sampled octopuses ranged from 56 to 250 mm in mantle length (ML) and 45 to 3178 g in body weight (BW). Mean octopus weight did not change monthly. Males were mostly mature while the majority of females were immature. Presence of some mature and a few spent females in all months sampled suggests that the population shows an extended spawning period. No spawning peak could be properly defined. Sex ratios did not significantly shift from the expected 1:1 in most samples. Females mature at a larger size (1234 g, BW; 165 mm, ML) than males (487 g BW; 114 mm ML). We recommend considering a minimum legal size of 1200 g BW. A year-long sampling programme for O. mimus should also be completed in order to detect any spawning peak.

High plasticity in cephalopod populations shows dramatic changes in their biological traits. Commercial catches of Mayan octopus (Octopus maya) in six localities of the state of Campeche, Mexico, were sampled monthly for five consecutive fishing seasons (2005–2009) in order to describe variations in population structure and maturation. Octopus maya grows and matures during the fishing season, from August to December. Spent individuals predominate in January and February, revealing a year-long life cycle. However, the presence of a few spent females in all months sampled suggests that a small part of the population shows an extended spawning period. Overall sex ratios did not significantly shift from the expected 1:1 in most samples. Males are mostly mature while the majority of females are immature during the season. Use of illegal fishing gears (spear diving or pots) in central localities accounts for a larger share in mature females. Octopus size showed large interannual and geographic differences. Females mature at a larger size (1024 g body weight, BW; 124 mm mantle length, ML) than males (484 g BW; 91 mm ML). Size at maturity in both sexes varies more between seasons than between localities. Female ML at maturity is larger than the current minimum legal size and implications for current octopus fishing regulations are discussed.

The digestive system of 36 paralarvae and 150 juvenile Dosidicus gigas were analysed to determine the diet. The early life stages were collected in the central and south region of the Gulf of California during different years and ranged in dorsal mantle length (ML) from 2.8 to 120.5 mm. The food content was separated first into identifiable material (IM) and non-identifiable material (NIM). All paralarvae contained only NIM stored mainly in the caecum rather than stomach. Juvenile squid feed on nine different prey types: euphausiids, copepods, amphipods, unidentified crustaceans, fishes, cephalopods, pteropods, bivalves and polychaetes. The IM were found mainly in the stomachs of juveniles with increasing number and diversity of prey in a function of increasing squid body size. In fact, juveniles from 60 to 120 mm ML had high stomach fullness percentages in half full and completely full stomachs suggesting improvement of swimming and hunting behaviour as they grow.

Stomach contents of 893 blue shark (Prionace glauca) caught off Ensenada, Todos Santos Bay, Baja California, from 1995 to 1997 were analysed. 614 had identifiable food remains. A large variety of pelagic cephalopods occurred in 55.5% of all stomachs and accounted for 46.2% of all prey and 84% by estimated weight of stomach contents. The most abundant (17%) and frequent (32%) was Histioteuthis heteropsis and the most important by estimated weight (22%) was ‘Gonatus californiensis’. Argonauta spp. and Vampyroteuthis infernalis were also abundant prey. A pair of beaks of giant squid Architeuthis sp. constitutes the first record for Mexican waters. Feeding habits and the probability of scavenging on mesopelagic cephalopods is discussed. The single most abundant prey was the pelagic, red crab Pleuroncodes planipes (41.7%). Other prey included teleost fish, amniotes and floating items. Diet varied greatly between months with no clear seasonal pattern. Tiny diet differences due to shark size or sex were inconclusive. A thorough review of studies on blue sharks stomach contents analysis is given. Blue shark feed on a large variety of passive pelagic prey, mainly mesopelagic cephalopods, that could be preyed upon as well as scavenged. Depletion of this predator due to overfishing may be leading to unknown cascading top-down effects in the mesopelagic realm.

Ovaries of 39 large jumbo squid Dosidicus gigas (415–875 mm mantle length (ML)) of different stages of maturity from the Gulf of California and Nicaragua were analysed. Oocyte development is asynchronous during female ontogenesis, with predominance (>85–90%) of small protoplasmic oocytes 0.1–0.2 mm in diameter for all stages of female maturity. Potential fecundity (PF) is determined at late immature stage II with average values around 18–21 million oocytes. The maximum PF estimated, 32 million oocytes, is so far the largest recorded for any cephalopod. PF is closely related to female size. Nicaraguan females, of smaller size (415–720 mm ML), show lower fecundity (5–15 million oocytes). Eggs were analysed in oviducts of mature females (540–875 mm ML), 7 from the Gulf of California and three females from Nicaragua. Eggs measured 0.9 × 1.1 mm in diameter and weighed 0.45 mg on average. The oviducts of the largest female (875 mm ML) held 1.2 million eggs, representing 4.6% of PF and no more than 14% of all vitelline oocyte stock of that squid. Variability in oviduct filling is very high and unrelated to ovary weight. However, a strong correlation was found between oviduct fullness and nidamental glands development. These observations suggest that spawning is extended and intermittent. A female spawns no less than half of the initial PF, and the minimal number of spawning activity events (egg batches) is roughly estimated at 8–12. During this terminal spawning stage females continue actively feeding and grow between egg-mass laying periods.

Stomach contents and carbon (C) and nitrogen (N) stable isotope analysis were used to evaluate trophic relationships of jumbo squid, Dosidicus gigas. Buccal masses, beaks and stomach contents of large and medium maturing-sized jumbo squid and muscle from its main prey, the myctophid Benthosema panamense, were collected in the Gulf of California, Mexico during 1996, 1997 and 1999. Both the quantified C and N-isotope ratios in muscle, and stomach content analysis revealed that larger-sized maturing squid showed a higher trophic position than medium-sized individuals. However, a discrepancy between stomach contents versus stable isotope analyses was found in evaluating trophic relationships. Simple dilution models as a function of growth were used to estimate the C and N renewal dietary shift for jumbo squid. Estimates of the initial C and N pools in D. gigas with an initial age of 70 days and 210 days indicated isotopic shifts of 32% after a threefold biomass increase and 25% after a fourfold biomass increase, respectively. Additionally, beak samples of jumbo squid were evaluated as an alternative tissue to estimate squid trophic position using stable isotopes. The results showed a significant correlation between stable isotope ratios from muscle and beak samples. Muscle isotope values were higher than beak by 1% and 4% for δ13C and δ15N respectively. A test with jumbo squid beaks collected from a stomach of a stranded sperm whale confirmed the viability of this method.

Stomach contents of 533 jumbo squid, Dosidicus gigas, ranging between 14·5 and 87·5 cm dorsal mantle length were collected on a monthly basis in the central Gulf of California from November 1995 to April 1997. Fish prey were identified by sagittal otoliths, cephalopods by beaks and crustaceans by exoskeletal features. The diet was dominated by Benthosema panamense, an abundant near-shore nyctoepipelagic myctophid that forms dense aggregations. Another myctophid, Triphoturus mexicanus, several micronektonic squid, pelagic red crab and small pelagic fish such as northern anchovy and Pacific sardine played a secondary role. The largest differences in diet were due to spatial and monthly changes, while differences regarding squid size or sex were smaller. Prey size (averaging 5–7 cm) and prey number did not vary with size of jumbo squid. Jumbo squid in the slopes of the Guaymas basin feed on abundant schooling mesopelagic micronekton of annual nature with a quick response to environmental changes, which could partly explain the large annual fluctuations of this commercial resource.