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STOCKTON FWO: Methods Developed for Marking Juvenile and Adult Delta Smelt
California-Nevada Offices , September 30, 2011
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Figure 1. Trays sitting on top of a circular holding tank during calcein marking of delta smelt. Shown are the pre-treatment to anesthetize fish (front tray), treatment (right tray covered with black plastic) and tray for washing off excess calcein from fish after completion of marking (back left).
Figure 1. Trays sitting on top of a circular holding tank during calcein marking of delta smelt. Shown are the pre-treatment to anesthetize fish (front tray), treatment (right tray covered with black plastic) and tray for washing off excess calcein from fish after completion of marking (back left). - Photo Credit: Gonzalo Castillo (USFWS).
Figure 2. Marking tray containing juvenile delta smelt. Fish are inside an egg incubation tray immersed in calcein.
Figure 2. Marking tray containing juvenile delta smelt. Fish are inside an egg incubation tray immersed in calcein. - Photo Credit: Gonzalo Castillo (USFWS).
Figure 3. Photonic marking for adult delta smelt. Photo on the right-bottom shows fish being marked in the anal fin. From left to right: Galen Tigan (FCCL), Michael Trask, Rene Reyes and Brandon Wu (U.S. Bureau of Reclamation).
Figure 3. Photonic marking for adult delta smelt. Photo on the right-bottom shows fish being marked in the anal fin. From left to right: Galen Tigan (FCCL), Michael Trask, Rene Reyes and Brandon Wu (U.S. Bureau of Reclamation). - Photo Credit: Gonzalo Castillo (USFWS).
Figure 4. Calcein-marked and unmarked delta smelt.
Figure 4. Calcein-marked and unmarked delta smelt. - Photo Credit: Jerry Morinaka (DFG).
Figure 5. Photonic marks on fins of adult delta smelt: A (green-dorsal), B (white-dorsal), C (blue-anal) and D (blue-caudal). Horizontal lines denote 1 cm.
Figure 5. Photonic marks on fins of adult delta smelt: A (green-dorsal), B (white-dorsal), C (blue-anal) and D (blue-caudal). Horizontal lines denote 1 cm. - Photo Credit: Jerry Morinaka (DFG).

By Gonzalo Castillo, Stockton FWO

As part of a three-year project funded by Delta Science, the Stockton Fish and Wildlife Office and cooperators evaluated marking methods for juvenile and adult delta smelt. Development of these methods played a critical part in the 2008-2009 mark-recapture evaluations of entrainment losses at the south Delta’s State Water Project, as reported in the U.S. Fish and Wildlife Service Journal on February 25, 2008 and August 7, 2009. A previous evaluation of striped bass predation further revealed no differences in consumption of marked and unmarked delta smelt (U.S. Fish and Wildlife Service Journal, June 24, 2010).

Culture and marking of delta smelt were conducted in close collaboration with staff from the University of California (UC Davis), the Fish Conservation and Culture Laboratory (FCCL), the California Department of Fish and Game and the U.S. Bureau of Reclamation.

Researchers evaluated the use of calcein as a primary mark for batch marking juvenile and adult delta smelt. Although photonic marking was not deemed feasible for juveniles, it was evaluated as a secondary mark for adult delta smelt. Laboratory trials were conducted on delta smelt raised in captivity to examine: 1) calcein mark intensity and post-marking survival for juveniles and adults (Figures 1, 2) and 2) photonic mark retention and post-marking survival of adults (Figure 3). The green fluorescence characteristic of calcein (Figure 4), and its intensity, were assessed with a calcein detector at six locations: scales, jaw, opercle, and pectoral, pelvic and caudal fins.

Adults were photonically marked in the fins: green-dorsal, white-dorsal, blue-caudal and blue-anal (Figure 5). Survival of calcein marked fish was high in juveniles (mean= 90.0%, SD= 5.1) and very high in adults (mean= 99.2%, SD=1.3). All marked juveniles and adults, and none of the control fish, showed marks seven days after exposure to low (2.5 g/L) and high (5.0 g/L) calcein concentrations and all immersion times (1-7 minutes). Calcein mark intensity was significantly higher in the jaw and pelvic fin of juveniles, and in the pectoral and pelvic fins of adults. Photonically marked adults (marked with 5.0 g/L calcein for 5 minutes) had very high post-marking survival at 70 days, ranging from 96.8% (blue-caudal) to 99.7% (white dorsal). Adult delta smelt had 100% mark retention at 102 days (calcein) and 97 days (photonic) following marking (95.3% of photonic marks were visible to naked eye and the remaining 4.7% were detected under a dissecting scope.

The main conclusions of this study were: 1) juvenile and adult delta smelt can be readily batch marked with calcein, resulting in high survival and mark retention over a period of weeks to months, and 2) the combined use of calcein and photonic marking for adult delta smelt resulted in high post-marking survival and 100% retention of both marks, for at least up to 3 months. These marking methods further enable identification of multiple groups while improving mark detection.

 


Contact Info: Gonzalo Castillo, 209-334-2968x323, gonzalo_castillo@fws.gov



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