Abstract
Evaluation of the movement patterns of small-bodied fish is often hindered by the lack of a suitable long-term mark. We evaluated several techniques for long-term group and individual identification of adult (40–70 mm total length [TL]) Oregon chub (Oregonichthys crameri). We marked Oregon chub with one of two different sized passive integrated transponder (PIT) tags (a 9 × 2.12 mm, 0.067 g PIT tag [PIT-tag] or a 8.4 × 1.4 mm, 0.033 g PIT tag [PICO-tag]), a red visible implant elastomer (VIE) tag, or a freeze brand. We monitored survival, tag retention, and mark quality over 150 days. In addition, we assessed the minimum length and weight thresholds to achieve 80% and 90% survival of PIT-tagged fish. Marking with a freeze brand, PICO-tag, or VIE tag had no effect on survival (P >0.05). In contrast, marking with a PIT-tag was associated with significantly lower (P <0.05) survival than in the control group. Survival was significantly higher (P = 0.002) for fish implanted with a PICO-tag than with the larger PIT-tag. The initial minimum TL for 80% and 90% survival was 54 mm and 64 mm TL, respectively, for the PIT-tag treatment. The 90% survival threshold for PICO-tagged fish was 44 mm TL. The 80% survival threshold was outside the range of sizes used in our experiment (<40 mm TL). Similarly, the 80% and 90% survival weight thresholds for the PIT-tag treatment were 1.5 g and 2.4 g, respectively, and the 90% survival threshold for PICO-tagged fish was 0.9 g. Tag retention was 94% and 95% in the PIT-tag and PICO-tag treatments, respectively; 80% of the freeze branded fish had easily recognizable tags after 150 days and 88% of the fish marked with VIE had easily recognizable tags after 150 days. PICO-tags, VIE marks, and freeze brands are all feasible long-term marking techniques for Oregon chub with negligible effects on survival through 150 days. The selection of a particular technique should be based on the study design and objectives (e.g., individual versus group identification), cost, ease, speed of tagging, and survival.
Highlights
Evaluation of the movement patterns of small-bodied fish is often hindered by the lack of a suitable long-term mark
At day 30, we observed no mortality in the control and freeze brand treatments and very low mortality in the sham injection and visible implant elastomer (VIE) treatments, which were not significantly different from the control (Figure 1, Table 2)
Our results suggest that PICO passive integrated transponder (PIT)-tags, VIE tags, and freeze branding are all effective methods for the long-term marking of small bodied fishes like Oregon chub
Summary
Evaluation of the movement patterns of small-bodied fish is often hindered by the lack of a suitable long-term mark. The small- and large-scale movements of small bodied fish (
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