The morphology and occurrence of jaw and operculum deformities in cultured barramundi ( Lates calcarifer) larvae

Morphological deformities are a problem that hinders the production of cultured finfish worldwide. Barramundi Lates calcarifer, like many other cultured species, suffers from a range of skeletal deformities including those of the jaw and opercula. This study describes the morphology of jaw and opercula deformities and their occurrence during the larval development of L. calcarifer. Samples of a minimum of 65 larvae were collected every second day at a commercial hatchery from 2 days after hatch (DAH) until 38 DAH. The jaw deformities recorded included shortened upper jaw, shortened lower jaw, twisted lower jaw and a deformity not previously described for any other species, termed ‘pinched jaw’, which affects both the upper and lower jaws. All jaw deformities were first observed at 18 DAH, 12 days after ossification of the affected structures. Deformities ranged in frequency between 4.24% and 35.71% of samples with no discernable pattern over time. The maximum frequency of the shortened upper jaw and shortened lower jaw deformities was 9.09% and 7.35%, respectively. ‘Pinched’ upper and lower jaw had a maximum frequency of 0.65% and 9.30%, respectively, while the co-occurrence of upper and lower ‘pinched’ jaw on an individual ranged in frequency between 0.00% and 3.90%. The twisted lower jaw deformity ranged between 0.00% and 7.79%. Jaw deformities co-occurred on the same individual for a significant proportion of the deformed population including shortened lower jaw and ‘pinched’ lower jaw, and ‘pinched’ lower jaw and ‘pinched’ upper jaw.