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Development of vision and the early feeding response of southern bluefin tuna larvae


Cobcroft, JM and Hilder, PI and Hart, NS and Battaglene, SC, Development of vision and the early feeding response of southern bluefin tuna larvae, Aquaculture 2013 - Book of Abstracts, 21-25 February 2013, Nashville, Tennessee USA, pp. 203. (2013) [Conference Extract]


A critical aspect of intensive culture of marine finfish larvae is investigating the appropriate lighting regimes, both in terms of light intensity and light quality (i.e. spectral characteristics) for optimal feeding success and ultimately high survival. Many marine finfish species have small larvae that hatch at an early stage in development. The successful transition of larvae from reliance on endogenous yolk reverses to predation on live prey is vital for survival. Early larval survival remains a bottleneck in the production of Southern Bluefin Tuna (SBT) (Thunnus maccoyii), in Australia. The primary goal of Clean Seas Tuna Ltd (CST) and Australian Seafood CRC-supported collaborative research projects, including this study, is to achieve the closed life-cycle production of SBT in order to underpin a sustainable aquaculture industry. SBT hatch at 3.3 mm and commence feeding on live prey by 3 days post hatch (dph). This study investigated the development of the SBT eye from hatching through to juveniles (32 dph, 40 mm) using histology and microspectrophotometry (MSP) to determine the spectral (colour) sensitivity of photoreceptors in the retina. Short-term (4 h) trials were used to assess the feeding response of SBT larvae between 3 and 9 dph, to determine the effect of light on feeding performance. At first-feeding, SBT have a single cone retina, which is typical of broadcast spawning marine finfish species. This retinal structure is usually associated with visual abilities in relatively high light conditions. However, while SBT were confirmed as visually mediated feeders and did not consume rotifer prey in the dark, they displayed similar first-feeding performance (proportion of larvae feeding and prey intake) across a range of light intensities (0.1 to 100 μmol s-1 m-2). On 6 and 9 dph, the proportion of larvae feeding decreased with increasing light intensity and was highest at 0.1 μmol s-1 m-2. A similar trend was found in prey intake on 6 dph, with the number of rotifers consumed per minute decreasing by almost half with increasing light intensity. There was no effect of light intensity on prey intake on 9 dph. Light colour also affected SBT feeding performance at 4 dph, with a higher proportion of larvae feeding and a higher prey intake under blue compared with red light, and intermediate feeding under white light. In a longer-term experiment, two levels of light intensity (24 and 49 μmol s-1 m-2) were compared during larval rearing, with no significant effects on SBT performance. Survival was -2% from stocking to 12 dph, with most early mortality occurring on 6 and 7 dph, with another increase in mortality after 12 dph. Growth was similar in the two light intensities, and larvae were 5.2 mm by 12 dph. Likewise, swimbladder inflation was not affected by light intensity and was 70% by 12 dph. With the spectral sensitivity of SBT obtained from MSP and initial results demonstrating differential feeding of SBT under different coloured lights, the effects of light intensity and light spectrum should be further examined in long-term larval rearing trials. These trials could not only assess feeding ability, but extend the assessment to behaviour and overall performance, with the aim to increase SBT larval survival, swimbladder inflation and growth.

Item Details

Item Type:Conference Extract
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Fisheries sciences
Research Field:Aquaculture
Objective Division:Animal Production and Animal Primary Products
Objective Group:Fisheries - aquaculture
Objective Field:Aquaculture tuna
UTAS Author:Cobcroft, JM (Dr Jennifer Cobcroft)
UTAS Author:Hilder, PI (Mrs Polly Hilder)
UTAS Author:Battaglene, SC (Associate Professor Stephen Battaglene)
ID Code:89374
Year Published:2013
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2014-03-04
Last Modified:2014-03-04

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