Fróðskaparrit - 01.01.1995, Side 107

Fróðskaparrit - 01.01.1995, Side 107
WHALEWORMIN THE FILLETS OF SAITHE FROM FAROESE WATERS 111 Year 1991 1992 1993 1994 Totals: infected físhes 125 38 68 31 262 not inf. físhes 4 2 22 15 43 total right 4,96 4,71 4,40 0,97 4,31 total left 8,70 8,87 5,63 1,71 7,10 stat. diff. *** * n.s. n.s. *** right A 4,09 3,05 1,92 0,15 2,72 left A 7,31 5,95 2,29 0,61 4,64 stat. diff. ** n.s. n.s. * *** right D 0,52 1,23 1,00 0,41 0,74 leftD 0,91 1,98 1,61 0,50 1,18 stat. diff. * n.s. n.s. n.s. ** right B 0,13 0,15 0,19 0,02 0,13 leftB 0,19 0,23 0,24 0,02 0,19 stat. diff. n.s. n.s. n.s. n.s. n.s. right C 0,07 0,05 0,21 0,07 0,11 leftC 0,02 0,28 0,11 0,02 0,09 stat. diff. n.s. n.s. n.s. n.s. n.s. of the standard deviation compared to the mean values (Table 2) reflect a general pat- tem in parasitologic examination, the ten- dency of high levels of variation. A slight decrease in infection levels with the time for the same age-group can nevertheless be seen in Table 2. This may be explained by an increase in the immune response effect from the infected fishes, as is suggested by Priebe et al. (1991). Decreasing infection levels in saithe from length group 40-49 cm are also reported by Scott (1985). The pooling of all fishes examined in Fig. 2, showing the distribution of the Anisakis simplex larvae in the fillets could be critisized. However, in an extensive sta- tistical analysis Novotny and Uzmann (1960) found no dependence between age of fish or geographical place, and the distri- bution of Anisakis sp. larvae in chum salmon, Oncorhynchus keta. The higher abundance found in the left side of the fish is striking (Fig. 2 and Table 3). The ventral parts A, D were statistically Table 3. Values of the mean for paired two sample t-tests for the difference in the num- ber of Anisakis simplex larvae in the right and left sections of saithe fillets, A, D, B, C, as in Fig. 2; *: p<0.05; **: p<0.01; ***: p<0.001; n.s.: not significant; stat. diff.: statistical difference (the table is comparing infected fishes only). Talva 3. Tøl fyri miðalvirðir frá paraðari t-test fyri munin í tali av Anisakis simplex ormverum í vinstru (left) og høgru (right) pørtunum av upsaflaki A, D, B, C, eins í Mynd 2. *: p<0.05; **: p<0.01; ***: p<0.001; n.s.: ikki signifikantur munur; stat. diff.: hagfrøðiligur munur (talvan samanber bert fiskar, ið eru infiseraðir). different when comparing the right and the left side, but not the dorsal parts B and C. Brattey and Bishop (1992) report the same difference for Anisakis simplex in the fillets of cod from Canadian waters. They also found significant difference between the bellyflaps (referred to as “the napes”). A similar distribution for Pseudoterranva de- cipiens in Canadian cod is reported by Brattey et al. 1990. Why the two different fish species saithe and cod do have uneven distributions of the nematodes in the musculature remains to be explained. One possible reason for the difference between the left and the right side could be the assymetry of the organs inside the body cavity. But this hypothesis is difficult to prove by experimental infec- tion. The comparison of saithe from Faroese waters with other areas in the North At- lantic is justified in Joensen and Táning (1970), who report considerable migrations to and from the Faroe area to Icelandic wa-
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