Effective Methods for Achieving Egg Take Goals

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 StrategiesEgg viability averages (green to eye-up).Eyed egg to smolt survival averages.Collecting adults needed based on annual

fecundity averagesUse adult age-class indicators for fecundity

average.Inventorying green eggsTake more eggs than needed to cover positive

virology testing results.Egg culling (surplus).

2010 ISSUERecord Fall Chinook returnGuidance 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 dam2. Natural origin parentage (integration

program)3. Sex ratio4. Limit the need to return excess adults (i.e.

hauling adults back up to LGR for release)*

Issues (cont’d)Pre-spawn mortalityGreen 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 OccuredEgg 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 200-300 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.

ConclusionsWhat 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?