The effect of dietary arachidonic acid 20:4ny6 on growth, survival and resistance to handling stress ž / in gilthead seabream Sparus aurata larvae

Ž . The effects of high dietary docosahexaenoic acid 22:6ny3, DHA and varying arachidonic Ž . acid 20:4ny6, AA were tested on growth, survival and resistance to handling stress in 5–35 day old gilthead seabream larvae. Three enrichment treatments differing in their DHArAA ratios Ž . Ž were fed to rotifers Brachionus rotundiformis and Artemia nauplii. The high DHA 35.9% . Ž . TFA enrichment treatment DHA-PL contained no AA and included lipid from the heterotrophically grown DHA-rich dinoflagellate Crypthecodinium sp. A second enrichment treatment Ž . AADHA , selected from an earlier screening study, supplemented the high DHA enrichment Ž . treatment with an AA-rich lipid 52% TFA from the heterotrophically grown fungus Mortierella Ž . alpina. A third enrichment treatment ALGA was the commercial product Algamac 2000, which Ž is devoid of AA, but includes approximately 12.9% of TFA as docosapentaenoic acid DPA, . 22:5ny6 . Rotifers fed the DHA-PL, AADHA and ALGA treatments demonstrated a range of Ž . Ž DHArAA ratios 20.9, 5.6 and 10.1, respectively as did the Artemia nauplii 25.8, 3.7 and 4.6, . respectively . The enriched rotifers were fed to larvae reared in 400 l V-tanks from day 5 to day 19 post-hatching. Following this period, larvae were exposed to controlled handling stress during transfer to 27 l aquaria, where they were then fed the enriched nauplii from day 20 to day 35 ) Corresponding author. Tel.: q972-7-6361443; fax: q972-7-6375761. Ž . E-mail address: [email protected] W. Koven . 0044-8486r01r$ see front matter q2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 00 00479-8 ( ) W. KoÕen et al.rAquaculture 193 2001 107–122 108 post-hatching. Although larval fatty acid profiles reflected the enrichment treatments, there were Ž . no marked differences P)0.05 in survival and growth in 5–19 day old larvae at the end of rotifer feeding. However, the larvae fed the AA enriched rotifers prior to the handling stress of Ž . transfer to the aquaria demonstrated daily and significantly P-0.05 lower accumulated Ž . mortality after transfer and during Artemia feeding than larvae fed the AA-deficient DHA-PL and ALGA-enriched rotifers. As larvae fed the ALGA, rotifers partially retroconverted DPA to Ž . Ž . AA in their tissues, the final survival 31.0% in these larvae was markedly better P-0.05 than Ž . Ž . larvae fed the DHA rotifers 17.5% , but significantly P-0.05 lower than larvae ingesting Ž . AADHA rotifers 42.9% . Conversely, the high-accumulated mortality in larvae fed the AA-deficient rotifers could not be corrected during the post-handling phase by feeding AA supplemented Artemia. The results suggest that dietary AA fed prior to handling stress improved survival more effectively than when fed following handling stress. These findings imply, as well, the importance of early larval nutrition on later larval and juvenile survival during crowding, grading and other handling stressors. q 2001 Elsevier Science B.V. All rights reserved.