How weather affects crawfish harvests

Date:
August 31, 2020
Source:
Louisiana State University
Summary:
To help inform farmers, researchers have quantified how rainfall
and temperature affect crawfish harvest yields.



FULL STORY ==========================================================================
The life cycle of a crawfish can be fairly straight forward. In the
summer months, crawfish reproduce in underground mud burrows with a
plug of mud on top of the burrow to protect them from predators. In
late summer and early fall, rain softens the mud plugs so the crawfish
can push their way out of the burrows and enter ponds, where they feed,
molt and grow throughout Louisiana's typically mild winters. Spring then
brings crawfish harvest season.


========================================================================== However, temperature and seasonal weather changes can affect this
life cycle.

Variability can have a costly effect on the industry, which has
experienced considerable growth over the past two decades. For example,
the 2018-19 Louisiana crawfish season produced 151.8 million pounds of
crawfish with an economic value of $209.5 million compared to 82 million
pounds valued at about $45 million in the 2004-05 season, according to
the LSU AgCenter. To help inform farmers, researchers at LSU are the first
to quantify how rainfall and temperature affect crawfish harvest yields.

"Providing farmers and producers with more information on how their
catch and livelihood may fluctuate due to environmental conditions
can help make them more resilient in the future," said LSU Assistant Professor-Research and the Southern Climate Impacts Planning Program
Climate Research Director Vincent Brown, who is the lead author on this
study published in Climate Research.

Brown and his colleagues analyzed eight years of crawfish harvest data
from six LSU Aquaculture Research Station ponds. They used a statistical
model to identify the most significant temperature and weather variables
that impact crawfish.

"The timing of precipitation is really important. The statistical
model shows that if you have heavy rainfall in August or September,
the crawfish harvest yields will be suppressed in the spring," Brown said.

Heavy summer rains can trigger the crawfish to emerge from their burrows
too early. When this happens, they enter ponds that could potentially
have low oxygen due to decaying plant matter and high summer heat as
well as a host of other things that could be harmful to their survival.

"We have seen how the low amount of dissolved oxygen in a pond can
directly affect the survival rate of crawfish. This issue is something
that we are continuing to study and develop best practices with the
farmers to combat," said C. Gregory Lutz, LSU AgCenter Aquaculture
Research Station professor, Louisiana Sea Grant College Program marine extension agent and study co-author.

Additionally, winter temperatures that drop below freezing can slow
crawfish growth.

This information can benefit farmers. For example, if excessive
precipitation occurs in August and September followed by a dry October
and November plus freezing conditions in January, farmers may not need
to set aside time and resources to harvest two to four days per week
in February, which is generally prescribed. It is possible that only
harvesting twice a week is sufficient, which can save farmers money on
bait, labor, gas and other costs, write the researchers.

"This study can also serve as a template to investigate the impacts
of weather on other farm-raised seafood products," said Mark Shirley,
Louisiana Sea Grant College Program and LSU AgCenter marine extension
agent and co-author of this study.


========================================================================== Story Source: Materials provided by Louisiana_State_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. VM Brown, MG Shirley, BD Keim, BD Marx, CG Lutz. Effect of
meteorological
variables on crawfish harvest in Louisiana, USA. Climate Research,
2020; 81: 15 DOI: 10.3354/cr01608 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200831094727.htm

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