German E. Merino

Development of California Halibut, Paralichthys californicus, Culture

Abstract In contrast to freshwater aquaculture and the culture of anadromous species such as salmon, marine fish culture is in its infancy. The small larval size of many marine species presents significant challenges to culture, however, these highly valuable fish offer considerable promise for aquaculture. A particularly attractive group for marine aquaculture is the flatfish. The California halibut, Paralichthys californicus, with a range in nature from Washington State south to Baja California Sur, Mexico is one such species. With the goal of enhancing the fishery for this species, a hatchery program was developed over a decade ago. The hatchery at Redondo Beach, California, maintains a group of adults that routinely spawn throughout most of each year. Further development of routine culture and juvenile growout techniques ultimately aimed at commercial aquaculture was initiated last year with support from the California Sea Grant College Program. Profitable commercial ventures culturing various flatfish species already exist in other parts of the world, but development of a flatfish culture industry in California confronts unique challenges. Two challenges in particular are the relatively high cost of energy and stringent environmental regulations. To meet these challenges, a culture system built around recirculation technology is being developed that would allow for an energy-efficient industrial-like approach to the culture of California halibut while minimizing environmental impacts.

Effect of Increasing Salinity on Weight-Specific Filtration Rate of Juvenile Scallop Argopecten purpuratus Reared at Two Temperatures: Is Any Effect Related to Ammonia Buildup?

ABSTRACT Larvae of the northern Chilean scallop Argopecten purpuratus (Lamarck, 1819) can be produced in hatcheries in closed aquaculture systems (CAS), and then early juveniles transferred to the sea for further grow-out. A new scallop mass production method from larvae to early juveniles that applies recirculation aquaculture system (RAS) technology has been developed at Universidad Catolica del Norte. RASs might lose water by evaporation, which increases salinity. Water temperature will increase as well if it is not controlled. An experiment was performed to determine the effect of varying salinity and temperature over water quality parameters and scallop physiological processes. Feeding behavior of A. purpuratus was determined under CAS with daily water exchange for hatchery-produced juvenile scallops (mean shell height, 26.5 mm; SD, 1.9) reared at salinities of 34, 38, and 42 g/L, and temperatures at 16°C and 22°C. Weight-specific filtration rates (WFRs) were analyzed at day 12 and again at day 55. Scallops were fed Isochrysis galbana and Chaetoceros calcitrans (ratio, 1:1). Results shows that WFRs analyzed for a 24 h period had a tendency to be lower at 0 h than at 24 h, for both temperatures; WFRs were higher at 22°C than at 16°C. A significant positive regression was also found between final WFR and total ammonia nitrogen (both NH3-N and NH4+-N) levels. Results presented here should be interpreted with caution outside the shell height range of 26.5 ± 1.9 mm. These results are applicable to the management of A. purpuratus under controlled conditions, such as a RAS.

Non-destructive method to study the internal anatomy of the Chilean scallop Argopecten purpuratus.

ABSTRACT Scallop aquaculture has a 20-y-old history in Coquimbo, Chile. At the beginning develop and introduce on industrial level the culture techniques was the main goal, but in recent years research to improve the broodstock quality has been introduced. Development of non destructive procedures to determine gonadal ripeness were necessary. The use of magnetic resonance imaging proved to be an interesting tool to view the internal anatomy of the Chilean scallop Argopecten purpuratus (Lamarck 1819) without any harmful side effect. A central groove located in the middle of the adductor muscle, became visible using MRI, and could possibly be related to the haemolymphatic circulation system.