Fecundity Management Strategies

Why Talk About This? As managers, we utilize various methods in managing broodstock collection – we never want to be short, but we usually do not want to be (too) over program! A two-edged sword. This discussion is based on past years experiences, most notably, the 2010 Snake River fall Chinook brood, and to establish the most effective methods for achieving egg take goals. This excludes low return years when adequate numbers of adults are available for broodstock.

Common Strategies Egg viability averages (green to eye-up). Eyed egg to smolt survival averages. Collecting adults needed based on annual fecundity averages Use adult age-class indicators for fecundity average. Inventorying green eggs Take more eggs than needed to cover positive virology testing results. Egg culling (surplus).

2010 ISSUE Record Fall Chinook return Guidance from M&E on adult needs based on age classification and historical length/fecundity criteria. Trapping protocols developed with respect to: 1. Handling and sampling at the dam 2. Natural origin parentage (integration program) 3. Sex ratio 4. Limit the need to return excess adults (i.e. hauling adults back up to LGR for release)*

Issues (cont’d) Pre-spawn mortality Green egg survival to smolt calculation for need THIS YEAR (2010) Adult length used as a guide for total number of females actually needed to meet green egg take goal. PIT tag data on adult returns – determining age structure of current run. Sampling rate at LGR – limits ability to “take” larger fish due to random protocol.

What Occured Egg size was near avg. / lower than expected fecundity. Fecundity average established for this collection site did not match hatchery 10-year overall averages Trapping rate was adjusted in-season (12% to 10%), potentially decreasing ability to collect “larger” adult females. Bigger 3–year-old females (a trend). 97.5% eye-up rate (historical avg. is 96%). Still came up nearly 200,000 eyed eggs short of program goal after all picking and inventoring.

How’s our inventory accuracy? We counted individual eggs in 12 random incubator trays to compare with average weight disposition – 1. One tray was 500 long, one 300 long, two 100 short – 2. Most trays were within eggs (on the plus side) of the average weight disposition. 3. First sub-yearling fry split (1.85 million) was approx. 1.47% under the population estimate from hatch to ponding. We have what we need. 4. M&E pick and sample a small portion of take based on tag data – does not account for overall picture!

What we’ll do next year! We’ve determined the composite average for fecundity of this stock over a 10-year cycle. It matches what we had in 2010, regardless of varying age/size criteria. We’ll collect enough females to meet the 10-year average AND the 10-year viability. Random green egg sample. Should be close!!! All adults collected at LGR utilized, minimizing or eliminating need to haul un-needed broodstock back for release. Late fish are in poor condition, anyway.

Conclusions What methods do you use? Historically Established #’s(virology, culling, viability) Provide some flexibility in broodstock management? Ability to cull eggs from hatchery stocks? We can do this for hatchery steelhead stocks (IHN sampling). Unfed fry releases relative to surplus? (current management policies prohibit this action). Raising excess fish can be costly, too! 1. Potential impacts to fish health (i.e. densities) 2. Potential costs associated with feed and chemicals.

Conclusions (cont’d) Transportation costs. Additional tagging costs. Additional operational costs (e.g. pumps).  We were within 5%, well below HGMP guidlelines.  Does not reflect well on hatchery management considering availability of broodstock to meet release goals.  With respect to M&E recommendations, the Hatchery needs to be more proactive in providing broodstock collection needs.

END! Questions and/or Comments?