Growth of Octopus vulgaris (Cuvier, 1797) in tanks in the Ebro Delta (NE Spain): effects of temperature, salinity and culture density

To assess the possibility of O. vulgaris ongrowing using tanks or cages in the bays of the Ebro Delta, we performed several growth trials of common octopus held in tanks. Effects of environmental factors (temperature and salinity) and zootechnical aspects (culture density) were studied. The thermal ranges that defined positive growth periods in the bays of the Ebro Delta were 19.5 degrees C to 23 degrees C (spring-summer) and 23.5 degrees C to 12.3 degrees C (autumn-winter), the latter being the most suitable period for ongrowing. Salinity did not affect survival (100%) or growth within the range tested (34-29 psu), though feeding rates (AFR. SFR) were directly related to salinity. On the other hand, after 60 days, final culture density increased three-fold (DI: 12.36 -> 44.37 kg m(-3); D2: 24.13 -> 67.76 kg m(-3)), with optimal survival results (> 90%) for the two densities tested. Growth and feeding rates showed a slight inverse relationship with density. Finally, growth and feeding rates showed a clear dependence on temperature in the two experiments (density and salinity). Our results conclude that industrial production of O. vulgaris in tanks is promising: this system offers an alternative to cages and allows for a more exhaustive control of culture.