Effects of photoperiod and light intensity on the survival, growth and feeding behaviour of larval striped wolffish (Anarhichas lupus)

Moret, Kelly J. (2002) Effects of photoperiod and light intensity on the survival, growth and feeding behaviour of larval striped wolffish (Anarhichas lupus). Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis investigated the impact of two environmental factors on the performance of larval striped wolffish (Anarhichas lupus). Specifically, I describe the impact of photoperiod and light intensity on the growth, survival, and feeding behaviour of larval wolffish. -- In the photoperiod experiment, larval wolffish were subjected to photoperiods consisting of 12 hours light/12 hours dark, 18 hours light/6 hours light, or 24 hours continuous light. Results showed that a photoperiod of 18L/6D yielded the best survival and growth after 50 days. Providing 24 hours light, a common technique in larviculture, did not offer any advantage in terms of survival or growth compared to the 18L treatment. The higher performance results seen for the 18L treatment is attributed to the similarity in photoperiod of the natural environment for the species. -- The investigation into the effects of light intensity on the survival and growth of larval wolffish compared intensities of 10, 40,160, 320, 750, and 1200 lux. For all values tested, survival and growth increased with increasing light intensity. A light intensity in the range of 750 lux-1200 lux produced survival rates of approximately 92.0% by day 50. -- The effects of light intensity (320 lux, 750 lux, 1200 lux) on the feeding and activity of larvae were also investigated. The frequency of feeding increased with increasing light intensity. The impact of light intensity was most significant during days 30-40, a period corresponding to the switch from endogenous to exogenous feeding in larval wolffish. During this period, the larval in the highest light intensity treatment (1200 lux) had significantly greater frequencies of feeding compared to the lowest light intensity treatment (320 lux). By the end of the study (day 50), there was no difference observed between treatments in terms of successful or unsuccessful foraging. -- For the production of larval wolffish a photoperiod of at least 18L in conjunction with 1200 lux is recommended for maximum growth and survival up to at least day 50 post-hatch.

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