40. Strontium and calcium levels in Japanese eel otoliths were described by Tzeng. Incorporation rates reflect the environment and changes in microchemistry are seen during migration from ocean to fresh water. In discussion, it was noted that the Japanese elvers move more rapidly into fresh water than does A. anguilla which may move between fresh and saline environments more than once.
41. Studies of body composition of A. bicolor and A. nebulosa in Sri Lanka presented by Ranawickrama showed gonadosomatic indices were strongly correlated with body length. The high protein content emphasized the value of both species as a food source. It was noted in discussion that the fat contents of yellow eels were too low for smoking.
42. Vithanage showed that weight and length of otoliths of A. bicolor and A. nebulosa increased linearly with body length of yellow eels. The nucleus, glass eel region and a number of fine rings were discernible under light microscopy.
43. Eel farmers in the Far East (as in Europe) often claim there are variations in performance of glass eels caught at different times and locations. A north-south cline of isozyme genotypes of A. japonica was found by Chan et al., possibly relating to differences in distances between spawning grounds and capture sites. Genetic variations were, however, not statistically significant. In discussion, reference was made to studies which suggested that there were no differences between Irish and Italian A. anguilla.
44. PCR amplification and RFLP studies of 5S ribosomal DNA of A. anguilla were reported by Martinez. He recommended appropriate DNA markers for future population/gene mapping studies.
45. Peters presented Verhijen and Flight's paper on commercial methods of slaughter. Salting, icing and spinal transection do not render eels brain-dead and the application of methods of humane killing should be considered. A video of the experiment was shown.
POSTERS
46. Tagliavini analysed genetic variability of cytochrome by sequences, using PCR techniques and showed that comparisons of eel from within Italy gave little evidence of variability while samples of A. rostrata were clearly distinct, supporting the theory of the existence of two species.
47. Gelin's poster giving estimates of production of eel by intensive culture in Europe led to the recording of additional information (Annex D). Over 6 000 t are produced, requiring an estimated 15 to 20 t of glass eel.
48. Appelbaum presented information on sex ratios among eels raised in culture. Morphometric parameters could be used to distinguish the sexes, in particular head length and body shape.
49. Hegedis described the effects of food deprivation and feeding on different sizes of eel fed with different levels of protein on ammonia production and oxygen uptake.
