Growth of young cuttlefish, Sepia officinalis (Linnaeus 1758) at the upperend of the biological distribution temperature range

摘要

Individual growth rates, feeding rates (%BWd(-1)) and food conversions for cuttlefish (S. officinalis) hatchlings and juveniles were determined during this study. A flow-through system was used. Water temperature reached 30 degreesC during the hottest part of the day, gradually decreasing to 25 degreesC during the night; salinity varied between 37 +/- 3 ppt and lights were kept on for 14 h day(-1). Hatchlings were placed in separate compartments with a water volume of 1.2 L. juvenile cuttlefish (from 0.5 to 25 g) were placed in bigger baskets, with a water volume of 5.2 L. Water flow was 120 L h(-1). The biggest cuttlefish used in these experiments (>25 g) were gathered in groups of five and placed in circular tanks (water volume of 250-300 L). Thus, results obtained in this case are means and not individual data. During the first 10, 20, 30 and 40 days, mean growth rates (of all individuals sampled by age group) decreased consistently (11.8 +/- 41, 9.8 +/- 1.8, 8.1 +/- 2.2 and 7.3 +/- 0.7%BW-1 respectively); in similar fashion, mean feeding rates decreased with age group (33.7 +/- 13.5, 22.0 +/- 7.9, 17.3 +/- 3.9 and 16.-7%BWd(-1) respectively). Mean food conversions varied between 3.6 and 2.5 between the age groups. When grouping results by weight class, similar patterns occur, as growth and feeding rates decrease consistently as cuttlefish grow bigger. Highest mean growth and feeding rates are obtained by hatchlings (<0.1 g) with 12.4 lus/minus> 4.5 and 35.3 +/- 15.1%BWd(-1), respectively, while the lowest growth and feeding rates were recorded for the largest animals, between 15 and 25 g (3.4 +/- 1.1 and 10.8 +/- 4.1%BWd(-1) respectively). For these weight classes, mean food conversions varied between 2.7 +/- 0.9 and 3.8 +/- 2.8.