NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Oscawana Lakeand Triploid Grass Carp

Lake Oscawana Civic Association Meeting

Putnam Valley Firehouse – 26 August 2012

Michael J. Flaherty – Region 3 Fisheries Manager

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Triploid Grass Carp

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Grass carpNatural Range:

• Native to the larger rivers of east Asia

Biology:

• Life Span: 14+ years in U.S. (mortality rate of 0.2)

• Growth: Stocked at 10" in spring and commonly grow to 18" by the fall

• Size: Up to 70 lbs in NY, reportedly up to 100 lbs in their native range

• Diet: By 8 inches in length they are "strictly" herbivorous– Reported to eat more than their weight in vegetation per day

• Sexual maturity: Age 3 or 4

• Spawning: Spring, in large river channels

• Tolerant of a wide range of environmental conditions (ponds, rivers, brackish)

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

• Introduced in US in Arkansas in 1963 and dispersed through Mississippi drainage

• Reproduced

• Diploid hybrid developed in 1970s but not effective

• Triploid hybrid developed in 1983 and effective

Stocking

History - US

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

• NYS study on Long Island 1985 – 1988

• Walton Lake EIS and multi year study

initiated in 1987

• First legal stocking under permit began 1990

Stocking History - NYS

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Triploid grass carp

(42 inches, 35 pounds)

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Triploid grass carp in NY

Current policy:

• The current simplified permit procedures apply for ponds meeting the following criteria:

● Pond is 5 acres or less in size

● Pond does not have a permanent outlet

● Pond lies wholly within the boundaries of lands privately owned

– Permits are issued for up to 15 fish/acre, all fish must be stocked on the same day between March 1 and November 30 for the year of the permit. After a pond has been stocked with triploid grass carp (TGC), two years must pass before additional TGC may be stocked

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Triploid Grass Carp Permits

Ponds not meeting the previous criteria must be reviewed following the procedures outlined in the State Environmental Quality Review Act (SEQRA)

• Ponds < 10 acres: Submit Short Environmental Assessment Form (EAF)

• Ponds > 10 acres: Submit Full EAF

• An addendum to each of these EAFs require additional information, that is specific to TGC stocking permit review, be sent along with the application to stock. (This may vary between DEC Regions)

• Occasionally a permit requirement may include post stocking monitoring

• For controversial or extremely large projects, a full Environmental Impact Statement (EIS) may be necessary

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Triploid Grass Carp in Lakes with

Permanently Flowing Outlets

• A barrier to triploid grass carp outmigration

will be necessary

• A permit may be needed for any

modification to a dam

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

•Over 5400 permits issued since 1991

(many reissued for the same waterbody)

•217 in Putnam County

•25 in Putnam Valley

(permit numbers through 2010)

Waters stocked in Region 3

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Lake Mahopac, Seven Hills Lake, Lower

Nimham, Palmer Lake, Lake Casse, Lake

Ossi, Lost Lake, Kentwood Lake, Lake

Sagamore, Tibet Lake, Lake Secor, Peach

Lake, Tonetta Lake, Lake Carmel, Spring

Lake

Larger Waters Stocked in

Putnam Co

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Vegetation control variable

Gradual results

Rapid results

Complete removal of vegetation in some larger waters

Incomplete removal in other large waters

What happened in southeastern NYS?

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Possible reasons for variable results

Stocking rates - stocking less than permitted

Vegetation biomass differences

15 – 19 TGC/veg ac = 30% reduction at

Walton compared to 100% at Mahopac

Initial wet wt veg biomass in Walton Lk

260% higher than Mahopac

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Vegetation type

Preferred species consumed first

Non-preferred species increased

in biomass and distribution

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Ecosystem Impacts

Reduced aquatic vegetation diversity

Walton Lk - Eurasian milfoil – increased as %

composition of aquatic veg from 43% to ~ 100%

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Reduction in vegetation-dependent fish

Walton Lake results

•Largemouth bass electrofishing catch rate decreased

47 % after all vegetation was removed

•Sunfish species electrofishing catch rate decreased

45 % after all vegetation was removed

Increase in non vegetation dependent fish

Walton Lake results

smallmouth bass catch rates increased 150%

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

2003 Walton Lake electrofishing results

suggest fisheries decline continued since the

eradication of vegetation:

•Largemouth bass catch rates declined 73%

compared to pre TGC stocking

•Sunfish catch rates declined 92% compared to

pre-TGC stocking

Many people feel fishing improves, or at least

does not decline, as long as vegetation is not

reduced to less than 30% of the littoral zone

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Water clarity

•Variable results – no net change in secchi readings in

Walton Lake and Lake Mahopac

•reduced clarity in 2 other southeastern NY waters

•For most waters we do not here of any change

•No net increase in nutrient cycling documented in studies -

possibly due to phosphorous uptake by TGC

NYS Department of Environmental Conservation

Fish, Wildlife & Marine Resources

Triploid Grass Carp -Nuisance or

Cure?

Bass anglers may say nuisance if

over stocked

Lake front owners may say cure

Biologists might say – it depends!

Beauty is in the

eye of the

beholder !