February 15-18, 2009 Washington State Convention Center Seattle ...

21
CONTRIBUTION POTENTIAL FROM WINTER BURROWING BROODSTOCK IN
LOUISIANA CRAWFISH PONDS
W. Ray McClain
Rice Research Station
Louisiana State University Agricultural Center
1373 Caffey Road
Rayne, Louisiana 70578 USA
rmcclain@agcenter.lsu.edu
Because crawfish aquaculture in the South depends on natural recruitment to populate ponds, and because harvest and recruitment
are continual, many producers are apprehensive about harvesting mature females early in the season for fear of adversely
affecting subsequent recruitment and thus, yields. Some farmers will delay harvest or return captured mature females back to
the pond during early harvests – typically a time of highest marketing prices – to ensure the greatest possible production. Aside
from the low efficiency of trap harvests, information on winter reproduction in Procambarus clarkii is sufficiently lacking to
justify this practice. Hence, this study was initiated to ascertain the typical spawning dates for winter burrowing crawfish.
P. clarkii dominate commercial crawfish ponds in Louisiana and have evolved to reproduce in burrows rather than in open
waters. For this reason, freshly constructed burrows along the levees of experimental crawfish ponds were flagged during the
winter months over a 2-year period, and then excavated at the end of each month. The unearthed females were placed in artificial
burrows in a lab that closely simulated conditions of the natural burrow, and were examined monthly for spawning activity.
Results are presented in the table below.
Spawning dates were positively correlated to month of burrowing, and it is assumed that maturation and spawning were little
affected by the move to the lab. Although no fresh burrows were observed during December in year 2, it appears that crawfish
that burrow later than December will not likely contribute offspring to the harvestable population within the current season
that typically ends by mid June in Louisiana. Hatchlings are not released until at least 5 weeks after spawning and because
January burrowers did not spawn until mid March or later in this study, it is unlikely such hatchlings could reach market size
in large numbers before ponds are drained. Therefore, it may be futile for Louisiana producers to protect mature females from
the harvest after about December, if at all, in commercial crawfish ponds.
Table. Mean spawning period and young hatched from crawfish burrowing during the winter months in
Louisiana crawfish aquaculture ponds.
Avg.
Ind.
Spawning
Range
Year 1 Year 2
Avg.
Month 1 of
No.
Young
per
Avg.
Ind.
Spawning
Range
Avg.
Month 1 of
No.
Young
per
Overall
Means for
Month of
Spawning
Month of
Burrowing Wt. (Months) 1
Spawning gram Wt. (Months) 1
Spawning gram 2
Dec 19.4 2 - 3 2.5 18.8 - - - - mid Feb
Jan 15.9 3 - 5 4.0 16.0 20.3 3 - 4 3.4 11.5 late Mar
Feb 25.6 4 - 5 4.2 10.5 23.8 4 - 6 4.7 9.6 mid Apr
Mar 25.6 4 - 8 5.7 15.5 20.8 5 - 6 5.2 - mid May
1
Months are indicated by numerical representation, beginning with 1 for January.
2
Young died before release from all females of the March group in Year 2.