The first-feeding response of larval southern bluefin tuna,Thunnus maccoyii(Castelnau, 1872), and yellowtail kingfish,Seriola lalandi(Valenciennes, 1833), to prey density, prey size and larval density

Abstract

We investigated the first‐feeding success of two species: southern bluefin tuna (Thunnus maccoyii) and yellowtail kingfish (Seriola lalandi) to determine if similar culture parameters can be used for both, especially when S. lalandi are held in the same tanks as prey for T. maccoyii. The feeding performance (proportion and intensity) was examined in three short‐duration (4 h) experiments: prey density, prey size and larval density. Increasing prey density from 0.5 to 25 rotifers mL−1 increased the proportion of T. maccoyii and S. lalandi larvae feeding. Prey size alone did not affect feeding in either species. Seriola lalandi had a decreased proportion of larvae feeding when larval density reached 50 larvae L−1 concurrent with a gradual increase in feeding intensity between 2 and 50 larvae L−1. In T. maccoyii, there was no pattern to the effect of larval density on the proportion of larvae feeding. The overall feeding performance of larvae was higher in T. maccoyii than S. lalandi. Increased prey density improved the first‐feeding ability of T. maccoyii and S. lalandi larvae. The effect of larval density on S. lalandi feeding requires further investigation, to ensure that they remain feeding when provided as prey in T. maccoyii culture. The identification of factors in this study, which increase first‐feeding success, will improve the culture of both species.

Factors affecting the feeding response of larval southern bluefin tuna,Thunnus maccoyii(Castelnau, 1872)

“…First‐feeding in T. maccoyii occurs at 3 dph (Hilder et al . ). For this paper, first‐feeding experiments refer to 3 dph larvae when larvae are exposed to live prey items for the first time.…”

“…The experiments were conducted in an experimental system comprising 24 individual 3 L black aquaria, as described in Hilder et al . () where optimum experimental conditions including larval density, prey density and prey size were determined. Briefly, the standard conditions, unless otherwise stated were: the aquaria were static with no water or air flow; light was provided by a single fluorescent tube (NEC tri‐phosphor 18 W, FL20SSBR/18‐HG, T8) with a light intensity of 30 ± 2 μmol s −1 m −2 ; larval density was 30 larvae per aquaria (for 3 and 4 dph experiments) and 20 larvae per aquaria (for 6 and 9 dph experiments).…”

“…Based on the first‐feeding results of this study and Hilder et al . (), early‐feeding experiments investigated the effect of light intensity and prey density on larval feeding response over an extended larval development stage encompassing 3–9 dph larvae.…”

“…The provision of optimum feeding parameters in culture leads to reduction in early mortality and improvement in health, growth and viability of marine fish larvae during their early life history (Naas, Naess & Harboe ; Parra & Yufera ; Downing & Litvak ; Benetti, Nakada, Shotton, Poortenaar, Tracy & Hutchinson ). An earlier study of first‐feeding T. maccoyii found an increasing proportion of larvae fed with increasing prey density, but there was a limited increase in feeding intensity (Hilder, Cobcroft & Battaglene ). It is important to investigate the potential benefit of high prey density to the response of older larvae, and whether feeding response changes during larviculture.…”

“…In addition , under comparative experimental conditions, T. maccoyii had a higher feeding response than other marine fish with oceanic larvae, including yellowtail kingfish, Seriola lalandi (Carton ; Hilder et al . ) and striped trumpeter, Latris lineata (Shaw ), which highlights the need to study the species‐specific early‐feeding requirements of bluefin tuna larvae.…”