Three tag types were tested: anchor tags, cheek tags and Coded Wire Tags (“CWT”s are tiny coded metal pieces injected into cheek muscle) externally identified by fluorescent elastopolymer tags (see Figure 1). A set of fish were also injected with oxytetracycline, a bone marker which is used for age analysis. This past February, after a year and eight months, we convened in San Francisco to end the study. NRFTS and Steinhart personnel worked side-by-side, capturing and sedating fish for photographing, inspecting tag sites, and drawing final blood samples. We had developed a method of cheek tagging rockfish which we assumed would produce less infection than the more invasive anchor tags. However, preliminary results suggest that any anchor tag infections were localized and encapsulated. Also, the retention rate for cheek tags was very disappointing. Almost all cheek tags (24 out of 26) were shed, or lost due to mortalities. Placing anchor tags through maxillary (lip) cartilage also fared poorly, with 15 out of 16 tags shed. Anchor tags attached through back muscle were retained comparatively well, with only 7 out of 20 tags lost, while only 1of 13 CWTs was lost. We found similar anchor to cheek tag recapture ratios in the field, confirming the laboratory results. Initially, the recapture rate of anchor vs.cheek tags was 1:1; however, the ratio now stands at 2:1 favoring anchor tags as the method of choice. Mortality was primarily among china (9 of 41 died) and black (5 of 14 died) rockfish, with gopher rockfish proving extremely hardy - only one death out of 44 animals. Complete blood counts, analysis of growth rates, and histology
of infection induced by tags are yet to be completed. Interesting findings
to date include high levels of fat revealed by necropsy; and
blood protein levels were about twice the baseline readings. Both conditions
probably reflect the comparatively plentiful feedings these fish enjoyed
at the aquarium. |