Refuge

DeltaSmelt1The Fish Conservation and Culture Lab (FCCL) and Genomic Variation Lab (GVL) of UC Davis have developed a breeding and rearing plan for creating the Delta Smelt refuge population. The goal is to minimize the deviation from the wild population, both phenotypically and genotypically. Currently the refuge population is in the eighth generation. To develop and maintain the refuge population requires a highly managed and labor intensive operation with a limited number of wild fish collected to breed into the culture population each year. To further protect the refuge population, we provide another hatchery, Livingston Stone National Fish Hatchery, in Shasta City CA, with a representative sample of the population each year.

Brief Description of the Process:

 Brood stock are sub-sampled prior to and throughout the breeding period (Jan – May). They are uniquely tagged (visible alpha-numeric tag, injected sub-dermally, near the dorsal fin), and a tissue sample (small fin-clip of caudal fin) is taken for genetic analysis (by GVL, UC Davis). Tagged females are checked for maturity twice weekly and their tag numbers are sent to the GVL, and the GVL provides a list of best combination of males and females. Based on the list, eggs are expressed and fertilized in vitro. The GVL has developed a genetic management plan (GMP) for the refuge population to monitor and ensure that the population is genetically similar to the wild delta smelt population. The GMP functions within the constraints of the existing aquaculture facilities by selecting about 250 pair crosses, single male and female fish, from the refuge population, including the wild fish each year, with the following goals: 1) maximize genetic diversity in the refuge population 2) minimize inbreeding in the refuge population, and 3) incorporate wild fish into the refuge population to minimize genetic drift. To manage 250 different full-sibling families, the FCCL combines eight families for rearing, as a “multi-family group” (MFG). Each of the MFG has 5600 live eggs, 700 from each family. The FCCL is able to maintain about 33-36 MFGs (264 – 288 families) of Delta Smelt. Between 50-100 wild fish are caught and bred into the population yearly. Three sets of intensive rearing systems are used to house the Delta Smelt as they grow: early larval start out in 130L-tanks, late larval have 400L-tanks, and juvenile – sub-adult stage tanks are reared in 1100L (5’ diameter) tanks. The culture methods are described in more detail in a report by Baskerville-Bridges and others (2005) and in a publication by Lindberg and others (2013).

 

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