Laserfiche WebLink
<br />auxiliary mark to the newly PIT tagged fish ~ 150 mm (Van Haverbeke and <br />Coggins 2002). Unfortunately, this type of auxiliary mark was found to be <br />unreliable as a diagnostic tool, because some marked fins regenerated and were <br />unidentifiable, and some fins thought to have been marked (punched) were never <br />in fact marked. Our experience with elastomer dye tags thus far has shown that <br />they are too unreliable to use as a long term secondary mark (Stone and <br />Sponholtz 2003). However, there may be potential for using elastomer dye to <br />test for short term loss of PIT tags (i.e., tags that are lost before the wound <br />heals). It was assumed during these studies that tag loss was probably <br />negligible, but concluded that future investigation might be warranted (i.e., other <br />type of secondary marking might be investigated). <br /> <br />The fifth assumption relates to the ability of field personnel to detect the <br />presence of a tag in a fish. This assumption was not evaluated directly; however, <br />our staff is trained in the proper operation of the PIT scanners and is exceedingly <br />careful to ensure that PIT scanners are in good working order. <br /> <br />Abundance estimates were calculated with the formulae presented by Seber <br />(1982) as: <br /> <br />NO = (M+IXC+l)_1 (1) <br />R+l ' <br /> <br />V[NO]= (M +lXC+IXM -RXC-R) (2) <br />(R+lY(R+2) , <br /> <br />Where NO, is the estimated number of fish in the population, V[NO] is the <br />estimated variance of the number of fish in the population, M is the number of <br />fish marked during the marking events (April and September trips), G is the <br />number of fish captured during the recapture events (May and October trips), and <br />R is the number of fish recaptured from the marked population during the <br />recapture events. The 95% confidence limits on our abundance estimates <br />assume a normal distribution and are appropriate given the ratios of RIG and <br />RIM observed (Seber 1982). <br /> <br />17 <br />