WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2012 55 After laboratory techniques were developed (Guitreau et al. 2012), high-throughput imaging to directly monitor ovarian morphological changes (Fig. 2) was conducted in collaboration with commercial hatcheries to select female broodstock for hormone-induced spawning in the production of hybrid catfish. The goal of the initial commercial trials was to assess the utility of ultrasonography as a noninvasive production tool to improve efficiency of egg collection. In May 2006, the reproductive condition of adult females (n = 84, 1.4 ± 0.3 kg [mean ± SD]) at Baxter Land Company commercial hatchery in Arkansas was assessed based on interpretation and subsequent classification of ultrasound images of ovaries prior to injection with carp pituitary extract. Females were grouped into three classifications: category 3, fair (developing ovary and oocytes, not likely to be strip-spawned, and minimal egg collection expected), category 4, good (advanced ovarian development, likely to be strip-spawned and to collect eggs), and category 5, excellent (mature ovary and oocytes, therefore highly likely to be stripspawned and to collect high quality eggs). As predicted, based on interpretation of the ultrasound images and consequent grouping of fish into classifications based on ovarian development, there were distinct differences in the number of fish that were strip-spawned and the number of fish from which eggs were collected among the three injected groups (Fig. 3). No eggs were collected from any (n =11) of the fish classified as having fair ovarian development (category 3). Of the total number of fish (n = 73) expected to be stripspawned for egg collection, 69 percent (n = 50) were manually strip-spawned (Fig. 3). Specifically the group of fish classified FIGURE 3. Adult channel catfish (n = 84) were grouped in three categories of ovarian development using ultrasonography. The number of fish injected with carp pituitary extract (green bars), strip-spawned (blue bars), and the volume of eggs (yellow bars) were recorded. Fish grouped in category 3 were representative of fish with ovarian development that would not be receptive to induced ovulation. Fish grouped in categories 4 and 5 were representative of fish with ovarian development close to or at physiological readiness for spawning. The strip-spawning and egg collection data demonstrate a clear division among the three groups by use of ultrasound imaging. Adapted from Guitreau et al. 2007. TABLE 3. The following table summarizes fish handling procedures used in studies of fish reproduction with ultrasonography 1. Common name Killed Submersed Restrained Anesthetized Position Time/Fish sturgeons N,Y Y NR N, Y D < 30 sec Neosho madtom N NR NR Y D NR Murray cod Y Partially Y Y D < 1 min Pacific herring Y Y Y N L Within s Atlantic cod N NR NR Y NR 20 - 40 s Atlantic halibut N Y N N L NR flounders N Y Y N, Y L 2 min haddock N Y NR Y D NR Atlantic salmon N Y NR Y D NR coho salmon N, Y Y Y Y NR NR steelhead N, Y Y Y Y D 4 min striped bass N Y NR Y V, D 1-4 min red hind N, Y NR Y NR NR NR sharks N, Y Y Y N, Y D, tilted ≤ 10 min thornback ray Y Y Y N V NR 1 Fish positioning was in dorsal recumbency (laying on its backbone), ventral recumbency (laying on the abdomen), and lateral recumbency (laying on one of its sides). N = No; Y = Yes, NR = not reported. Data was adapted from Table 4 (Novelo and Tiersch 2012). (CONTINUED ON PAGE 54)
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