Electroshocking and PIT Tagging of Juvenile Atlantic Salmon: Are There Interactive Effects on Growth and Survival?

Abstract

Electroshocking and tagging of fish with passive integrated transponder (PIT) tags are two commonly used methods for conducting mark-recapture studies in freshwater environments and are frequently used in combination. We conducted an experiment to test for the effects of electroshocking, tagging, and a combination of electroshocking plus tagging on the growth and survival of Atlantic salmon Salmo salar parr. We used five treatments that included the presence or absence of PIT tags and electroshocking at 300 or 500 V plus a control group. Fish were measured, weighed, and electroshocked on four occasions separated by approximately 2-month intervals. The average (Ϯ1 SD) fork length was 62.1 Ϯ 1.9 mm and the average weight was 2.5 Ϯ 0.3 g at the start of the experiment; at the end of the experiment, length averaged 120.5 Ϯ 11.6 mm and weight averaged 20.9 Ϯ 6.1 g. We did not detect any significant effects of electroshocking on growth or survival over the course of the experiment. However, there was evidence that tagging negatively influenced survival over the first interval after initial tagging and that survival was positively correlated with fish size. In addition, tagged fish seemed to suffer a minor depression in growth over the first interval, although differences in size among tagged and untagged fish were nonsignificant throughout the course of the experiment. We suggest that the size at tagging may have a greater effect on survival and growth of small (Ͻ80-mm) Atlantic salmon parr than the amount of exposure to electroshocking.

Effects of passive integrated transponder tags on survival and growth of juvenile Atlantic salmon Salmo salar

“…The majority of mortality (80%) occurred in fish 80 to 84 mm FL. This is in agreement with results from other studies that typically report higher mortalities in smaller individuals following tagging [18,21,24,25]. For example, Acolas et al [21] demonstrated that increases in length of juvenile brown trout (41 to 70 mm FL) significantly enhanced the probability of survival after implantation of 11.5 mm PIT tags.…”

“…For example, Acolas et al [21] demonstrated that increases in length of juvenile brown trout (41 to 70 mm FL) significantly enhanced the probability of survival after implantation of 11.5 mm PIT tags. Similar results have been reported for Atlantic salmon parr (60 to 69 mm FL) using 11.5 mm PIT tags [24].…”

“…However, this was compensated for 30 days after tagging by increased growth of the tagged fish. Similar results have been found for juvenile brown trout (41 to 70 mm FL) and Atlantic salmon (60 to 69 mm FL) up to 60 days after implantation with 11.5 mm tags [21,24]. Tatara [13] demonstrated that the probability of experiencing positive growth in steelhead parr (45 to 96 mm FL) implanted with 12 mm PIT tags was size-dependent, and it was concluded that length at implantation should be above 74 mm FL to avoid negative growth.…”

“…Several other studies have reported depressed growth after tagging, but there is much variation in the extent and duration of this impact, depending on factors such as species, size, and environmental conditions [12,14,18,21,24]. Bateman and Gresswell [14] showed decreased growth in juvenile steelhead (73 to 97 mm FL) during the first 20 days after surgical implantation of a 23 mm PIT tag.…”

The use of visual and automatized behavioral markers to assess methodologies: a study case on PIT-tagging in the Alpine newt

“…The absence or delay of growth can be explained by stress induced by tagging. In fish studies, while some authors did not report any effect of PIT-tagging on growth (Acolas et al, 2007;Lee et al, 2009;Navarro et al, 2006), others researchers found a reduction in short-term growth (Baras, Westerloppe, Mélard, & Philippart, 1999;Lacroix, Knox, & McCurdy, 2004;Sigourney, Horton, Dubreuil, Varaday & Letcher, 2005). Cucherousset, Paillisson, and Roussel (2007) found that the effect on growth was independent of the size of their studied fish, whereas Greenstreet and Morgan (1989) determined that a minimum size of 160 mm for Atlantic salmon prevented a tag effect on growth.…”