Graduation Year

2011

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Marine Science

Major Professor

Frank E. Muller-Karger

Keywords

Centropomus undecimalis, larvae, Snook, standard length, temperature, yolk volume

Abstract

In an effort to determine the optimal temperature for rearing Centropomus undecimalis larvae during the yolk resorption period, larval development was measured under four different temperature regimes (23, 25, 28 and 31 °C). The eggs were incubated at 28 °C until hatching, which occurred at about 17 hours post-fertilization. After hatching, temperatures were adjusted to the respective treatment levels. Measurements were collected from 25 individual larvae across rearing temperatures at the following pre-determined time intervals: at hatching, 24 hours post hatch (hph), 48 hph, and 72 hph. Morphometric measurements were obtained from photomicrographs, including yolk sac length and height, oil globule diameter, standard length, body height at anal pore, and eye diameter. Larvae in the 25 °C treatment had longer median standard length, body height, and more energy reserves than those larvae reared at other temperatures. The yolk sac and oil-globule were present up to 72 hph at 23 and 25°C, while these were entirely consumed after 48 hph in treatments at 28 and 31 °C. Centropomus undecimalis larvae had the highest growth rates during the first 24 hph, and this period corresponded to the highest energy consumption as determined by the decrease in yolk-sac and oil-globule volume. Survival was assessed during the third trial only. The 31 °C treatment presented the worst survival percentages, with a maximum survival of 37.2% at 24 hph, and 100% mortality at 72 hph. The 25 °C treatment featured higher survival at the end of the trial than the other treatments with 1.7% survival. Eye diameter didn't vary significantly with time and was not a useful parameter for tracking development during yolk resorption. These results led to the conclusion that 25 °C was the optimal temperature to raise snook larvae during the yolk-resorption period.

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