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15 pages, 4 tables, 2 figures.-- This is an open access article distributed under the Creative Commons Attribution License, This study focuses on the extraction of nutritional and healthy constituents of whole by-products resulting from the commercialisation of Patagonian squid (Doriteuthis gahi). By-products corresponding to squid individuals captured at different seasons were comparatively analysed for proximate composition, lipid classes content, fatty acid (FA) profile, and macroelement and trace element composition. As a result, moisture, lipid, protein, and ash values were included in the ranges 829.0–842.8, 17.5–21.8, 106.0–123.7, and 9.3–13.3 g·kg−1 by-products, respectively. Phospholipids showed to be the most abundant lipid class (359.2–463.5 g·kg−1 lipids), while triacylglycerols were only present in a 9.5–13.1 g·kg−1 lipids range. Valuable levels were detected for α-tocopherol (539.6–973.3 mg·kg−1 lipids), polyunsaturated fatty acids (PUFA; 50.5–52.6 g·100 g−1 FA), ω3 PUFA (47.0–48.6 g·100 g−1 FA), PUFA/saturated FA ratio (1.4–1.6), and ω3/ω6 ratio (12.1–13.4). Among macroelements, S, P, and Na showed to be more abundant than K, Mg, and Ca. Profitable levels of Co, Cu, Fe, Mn, Se, and Zn were detected in all kinds of individuals. In spite of content variations found as a result of the capture season of Patagonian squid individuals, whole by-products of this cephalopod species can be considered as a profitable source to provide the food and pharmaceutical industries with useful value-added constituents, This research was funded by the Spanish Ministry of Research and Innovation, grant number RTI2018-095659-B-I00 (2019–2022)

Population genetic structure of the Patagonian longfin squid Doryteuthis gahi was assessed across the Falkland Islands, central-southern Chile, and Peru. Microsatellite and mtDNA data partitioned samples into two groups: one consisting of the Peruvian samples, the other comprised the Chilean and Falklands samples, with no sub-structuring within either group. Recurrent demographic independence between groups can be linked to abrupt changes in continental shelf features between the Peruvian and central Chilean sites restricting adult dispersal. Phylogeographic analyses indicate a prolonged period of isolation between the Peruvian and Chilean–Falkland groups which may include divergence in allopatric glacial refugia. Both groups have experienced dissimilar historical population size dynamics with the Peruvian population exhibiting signals of size fluctuations, similar to other species in the area, that align with postglacial changes in the productivity of the Humboldt Current system. Genetic cohesion among central-southern Chilean and Falklands samples supports connectivity across current management boundaries and indicates that phenotypic differences between D. gahi from these areas reflect plastic responses to environmental heterogeneity. The study adds to evidence that loliginid squids typically display connected populations over large geographical areas unless specific oceanographic features restrict gene flow. Recognition of the Peruvian and Chilean–Falklands groups as distinct evolutionary significant units is recommended.

Coastal spawning grounds of the squid Doryteuthis gahi were identified for the first time at three sites in Central Chile during 2014 and 2015. A total of 15 egg masses were collected from between 10 and 15 m depth and brought to the laboratory for evaluating capsular, embryonic and when possible, paralarval characters. Egg capsules from all spawning areas were similar in size (∼25 mm in length) and number of embryos per capsule (∼15). Egg-laying patterns, in addition to field observations, suggest that relatively small D. gahi may be using shallow waters in semi-protected environments to reproduce and spawn. Additionally, the differential use of healthy versus defoliated kelp Lessonia trabeculata suggests that egg-laying females selectively choose substrata that limit mechanical damage to the fragile egg capsules and that also allow for adequate water flow, which could be reduced in a mass of kelp fronds. These findings highlight the opportunistic behaviour of D. gahi which use overgrazed L. trab...

Light reflecting structures (iridophores) were examined in live Doryteuthis gahi with mantle lengths (ML) between 50 and 420 mm, both during trawl surveys onboard ship and in shallow-water spawning grounds (10–15 m depth) by SCUBA divers around the Falkland Islands. Several types of iridophores were distinguished based on their shape, colour reflection and position on the body. Ventrally, silvery iridophores cover pigmented organs such as the eyeballs and ink sac and might be used for countershading the squid body. Pink iridophores (splotches) cover the whole mantle, head, fins and arm bases. Green-red iridophores on the dorsal side of the eyeballs, as well as pink splotches on the dorsal and lateral mantle, head and arm bases can be either uncovered or masked by overlaying chromatophores. Two specific bright green stripes of iridophores develop under the fins only in females with ML .80 mm; these may be involved with distant sex recognition, both in forming unisex schools and in ‘preliminary mating’ in the twilight feeding grounds located at the shelf edge. During solitary egg laying in shallow waters, females mask these green stripes almost completely using the overlying chromatophores.

The Falkland Islands fishing industry is unique, as 60-80% of its annual catch consists of two squid species, Illex argentinus and Doryteuthis gahi. Short annual life cycles make both species susceptible to intra-annual environmental changes, resulting in large biomass fluctuations that must be addressed in management of the stocks. In the D. gahi fishery, short chains of communication between science, management and industry allow effective cooperation in the interest of long-term sustainable exploitation. The industry is responsive to short-notice requests for in-season information about the fishery. Management takes into account both scientific advice and industry recommendations, through ongoing consultations before and during the fishing seasons. As a result of this cooperation, D. gahi is one of the best managed squid fisheries in the world with local fishing companies being amongst the largest and most profitable enterprises in the Falklands economy. The I. argentinus fishery has the same potential, but a further level of cooperative management is needed as this squid is a straddling stock between several countries and the high seas. Development of a regional fisheries management organization in the South Atlantic Ocean is required to control multilateral exploitation and ensure long-term sustainability of I. argentinus stocks.

A unique observation was made of the cold water squid Doryteuthis gahi spawning in Patagonian shelf waters near the Falkland Islands, South Atlantic. This represents the first recorded observation of spawning behaviour for this species. In contrast to other loliginids, which spawn in large mixed-sex aggregations, a solitary female was observed adding a single egg capsule to an existing egg mass on a kelp stipe, (Lessonia trabeculata). If this behaviour is characteristic for this species then it represents a departure from normal loliginid spawning behaviour and is in agreement with the observed absence of D. gahi aggregations over spawning grounds.

8 pages, 3 figures, 5 tables, The stomach contents of three squids: 57 Doryteuthis gahi with mantle length (ML) ranging from 7.0 to 37.0. cm, 75 Illex argentinus (21.0-32.8. cm) and 116 Onykia ingens (19.9-39.3. cm) from commercial catches on the outer Patagonian shelf grounds during autumn (March and April 2012) were examined to describe their diet and compare their trophic spectrum. D. gahi preyed on 12 different items, I. argentinus on 20 and O. ingens on 29. Prey diversity increased with the sizes of the squids. Along growth, D. gahi shifted from crustaceans, mainly euphausiids to fish (Salilota australis) and squid (D. gahi and Histioteuthis sp.). Small to mid-sized I. argentinus and O. ingens consumed mostly two fish, two squid species D. gahi and Histioteuthis atlantica, two crustaceans Munida gregaria and Munida subrugosa and the Chaetognatha Sagitta elegans. All the three species show a high prey overlapping at similar sizes: Squid of smaller size (5-15. cm ML) fed mainly on crustaceans: D. gahi on euphausiids and squat lobsters (Munididae). Mid-sized squid fed mainly on fish, most frequently Gymnoscopelus sp. and S. australis, and larger I. argentinus and O. ingens fed mostly on squids, including cannibalism. The overlapping of the diet of similar sized squid was large suggesting all preys are abundant species in autumn in the water column in the Patagonian Shelf. © 2013 Elsevier B.V., Rigoberto Rosas Luis was supported by CONACyT (Con-sejo Nacional de Ciencia y Tecnología, México)