Onondaga Lake – Recruitment Discussion

Onondaga Lake Technical Advisory Committee

October 31, 2012

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YOY Community Structure from Seining Events

L09.28_YOY-CPUE_Community_over_time.xlsx L09.27-Fig_A8-15_YOY_CPUE.xlsx

• Lowered reproduction in Lepomis since 2006– Number of nests remains high, with little evidence of

recruitment during seining events

• Several other species also have lower reproduction

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Lowered Reproduction in Lepomis

• Factors to consider to evaluate causes– Alewife predation– Nest predation by round goby and other

predators– Increased macrophytes

• Protection from wave action on eggs• Cover for fry and juveniles• Other species that benefit from increased

macrophyte coverage, including brown bullhead, largemouth bass, and yellow perch, have been increasing in abundance in electrofishing surveys

• Evaluate population status in nearby lakes– Is this a regional observation?

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Sampling in 2012

• Larval trawls replaced with larval seines (two events)

• Juvenile seining – Additional location within each stratum with little or no

macrophytes– Started 2 weeks later in mid-July

• Added one littoral zone juvenile electrofishing event in late July at five transects (one per stratum)

• Modified pelagic gillnet sampling– Two net sets per stratum perpendicular to shore at

night

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Future Sampling Considerations

• Diet sampling in alewife • Macrophyte surveys

– Conduct two times within 5-year timeframe• 5-year assessment and one additional aerial survey

at year 2 or 3

• Additional alewife sampling in fall– Gillnetting, hydroacoustics, or both?

• Zebra mussels– Is current program sufficient to understand

how they may be impacting Onondaga Lake?