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Airport Road, Falkland Islands

The channel bull blenny Cottoperca gobio (Notothenioidei, Perciformes) is the largest species of the family Bovichtidae that inhabits both the shelf and upper slope around the southern tip of South America. It is a common non-retained bycatch species during finfish bottom trawl fisheries on the Patagonian Shelf in the Southwest Atlantic. The present study aimed to address previously unknown aspects of its spawning, egg development and early larval growth by maintenance of adults in an aquaculture facility. The fish spawned in the beginning of austral spring (early September), adhering the eggs to the wall of the tank in a band of about 120 cm long, and 20–25 cm wide, estimated to contain ~170,000 eggs. Before and after spawning, the body colouration of both sexes changed displaying marked sexual dimorphism. The male did not guard the spawning site. Egg sizes varied between 2.1 and 2.4 mm. Eggs had a characteristic oil droplet inside. Embryogenesis lasted 50 days, constituting 305 accumulated degree-days. Newly hatched larvae were 7.8–8.1 mm total length, having the oil droplet inside their yolk sac. The yolk sac feeding period lasted approximately 9 days. Anterior part of the larval body was heavily pigmented such that pigmentation could be used for identification purposes. C. gobio occupied the very r-end of the r/K continuum among demersal notothenioid fish, characterised by high fecundities, small eggs and larvae, lack of parental care and high growth rates enabling it to populate the vast areas of the Patagonian Shelf whilst competing with other abundant large demersal fish predators. © 2014, Springer-Verlag Berlin Heidelberg.

Rock cod Patagonotothen ramsayi (Regan, 1913) is one of the most abundant fish of the family Nototheniidae inhabiting the Patagonian Shelf and upper Slope in the southwest Atlantic. Recently, P. ramsayi became an important commercial species around the Falkland Islands with annual catch of 60,000-75,000 t. The present study aimed to reveal previously unknown aspects of reproductive biology of P. ramsayi during the first successful maintenance of adults for more than a year in an aquaculture facility with running seawater. The fish spawned at the end of austral winter. During spawning, males changed their coloration dramatically, occupied artificial shelters on the bottom and showed aggressive territorial behaviour. Egg masses were light-yellow to light-orange irregular spongiform. They were negatively buoyant, but located outside shelters and were ignored by males. Egg diameters varied between 2.1 and 2.3 mm, and the number of eggs per egg mass ranged from 26,800 to 123,400. Embryogenesis lasted 28-32 days. Total lengths of newly hatched larvae ranged from 6.2 to 6.7 mm. The yolk sac feeding period lasted approximately 11 days, during which the larvae showed negative phototaxis. One-month-old larvae attained 8.8-9.0 mm in length. This study confirms that P. ramsayi exhibit the reproductive strategy typical for nototheniid species occupying low-latitude peripheries of their distributional range, characterised by a combination of r-features (small eggs and larvae, high fecundity) and K-features (territorial behaviour and possible nest guarding). © 2013 Springer-Verlag Berlin Heidelberg.

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