Rate and efficiency of yolk utilization in developing eggs of the sole Solea solea

Abstract

1. The eggs of Solea solea, like many other marine planktonic fish eggs, are characterized by a high water content (91%) and a relatively low calorific content (5800 cal/g dry organic substance). Demersal fish eggs, on the other hand, have, according to the information available from literature, a low water content (about 75%) and a high calorific content (6500 cal/g dry organic substance). 2. Older embryos and freshly hatched larvae of Solea solea secrete large quantities of slime upon brief exposure to distilled water; this makes the estimation of their dry weight and calorific content difficult. Slime secretion could be reduced to a certain extent by killing the larvae in 5% sea-water formalin prior to distilled water exposure (to remove adhering salt water). 3. At 10°C, incubation lasts 176 hours and freshly hatched larvae contain 85.2% of the energy contained in a freshly laid egg (0.49 cal/egg); at 15°C and 20°C, the corresponding values are 80 hours, 79.0% and 53 hours, 75.5%, respectively.