FBA Issue 4: September / October 2005


Skeletal deformities in fish larvae





Marine fish are poorly developed at hatching. They undergo important functional and morphological changes during the larval period. Several parameters could influence this development and negatively affect the larvae quality.


In the wild, malformed animals rarely survive because of the forces of natural selection. But in hatcheries, larvae with many morphological anomalies survive.


Comparison of normal larva and larva with head deformities


The morphological deformities in larvae result from disruptions in the skeletal developmental process. They cause lowered growth, high mortalities, reduced market value of the product, and consequently a significant loss for the farmer.


The most common skeletal deformities observed in hatcheries include spinal malformations (lordosis, scoliosis, coiled vertebral column), deformed operculum and head (jaw and neurocranium) malformations.


Farmers often suspect that diets induce malformations. The link between nutrition and malformations has been difficult to demonstrate because marine larvae are fed on live prey and the nutritional composition of the live organisms cannot be easily manipulated.



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