Big Rivers Blue Catfish Final Report

Blue catfish (Ictalurus furcatus) are native to the Missouri and Mississippi rivers, and support extremely
important fisheries on these big rivers. The Missouri River supports a recreational fishery, and the
Mississippi River supports both recreational and commercial fisheries. Missouri’s big river, blue catfish
populations have not been intensively researched or managed in the past, and information needed to
inform management and regulatory decisions is lacking. Blue catfish were sampled in the Mississippi and
Missouri rivers using low-frequency electrofishing, and these data, along with tag return information,
were used to estimate exploitation and other population demographics (e.g., size structure, age and
growth, and total annual mortality). Management and regulatory recommendations focus on increasing
yield available to fishers and ensuring sustainability of big river, blue catfish populations.
During 2015 and 2016, a total of 6,639 blue catfish ranging in size from 3-53 inches (76-1,348 mm) total
length (TL) were collected from eight study sites. Pectoral spines were aged from 1,874 blue catfish;
ages ranged from 1-19 years on the Mississippi River and 2-18 on the Missouri River. In the Mississippi
River, fish reached 15 inches by age 4, 18 inches by age 5, 24 inches (5 pounds) by age 8, 30 inches (10
pounds) by age 11, and 38 inches (20 pounds) by age 17. Missouri River blue catfish were estimated to
take an additional year to reach the same lengths. To estimate exploitation, we tagged 759 blue catfish
in the Mississippi River and 915 in the Missouri River, with approximately 70 percent of tags having a
standard reward value ($25) and the remainder having a high reward value ($150). As of 1 January 2019,
311 blue catfish tags were reported by fishers. Reporting rates differed between sites and rivers;
reporting rates on the Mississippi River ranged from 63-100 percent and from 40-88 percent on the
Missouri River. Total annual exploitation was 10 percent (6 percent for recreational harvest and 4
percent for commercial harvest) on the Mississippi River and 12.7 percent (all recreational harvest) on
the Missouri River. On the Mississippi River local exploitation ranged from approximately 7 percent at
site 2 to 16 percent at sites 1 and 4. Local exploitation on the Missouri River was lowest at sites 5 and 7
(9 percent), slightly higher at site 8 (11 percent), and highest at site 6 (18 percent).
Growth or recruitment overfishing was not evident when we incorporated size-specific exploitation
rates in our simulations. If fishing effort remains steady, our models predict that a minimum length limit
(MLL) would offer the greatest improvement in yield and would have the added benefit of improving
trophy fishing potential. Furthermore, recreational anglers are thought to be more supportive of a MLL
to improve chances of catching a trophy-sized blue catfish as opposed to other regulations including
gear restrictions or reduced daily bag limits. Commercial fishers may also support a MLL given the
predicted increase in yield. Therefore, fisheries managers aiming to increase yield on the Mississippi and
Missouri rivers should consider a MLL (e.g., 18 or 21 inches TL). In our simulations a protected slot limit
of 26-34 inches, like that at Lake of the Ozarks and Harry S. Truman Lake, improved the trophy fishing
potential more than predicted with a MLL, but decreased yield by 20-34 percent. If public opinion favors
trophy fishing potential and fishers are willing to accept a minimal decline in yield, then restricting the
number of fish over 30 or 34 inches per day should be considered, as well. This option would be most
appropriate on the Missouri River where maintaining or improving yield is not currently a management
objective.2
Recommendations:
- Complete data analysis and final report for flathead catfish during FY2020.
- In coordination with Outreach & Education Division staff develop a communication plan during
FY2020. Inform stakeholders about the outcomes of this research and determine constituent
attitudes and opinions concerning catfish harvest regulations and management objectives.
o Survey recreational and commercial catfish fishers during FY2020, to determine
attitudes and preferences associated with catfish management, angling, and harvest.
o During FY2020 inform and coordinate with neighboring state agencies (IL, KS, KY, NE,
and TN) responsible for managing border water fisheries.
o Conduct public meetings during FY2021.
- Based on the results of this study (blue catfish and flathead catfish final reports), public input
(catfish harvest survey and public meetings), and discussions with neighboring state agencies:
o If public sentiment is similar to existing human dimensions data (i.e., fishers are in large
part harvest oriented):
▪ Coordinate communication, planning, and development of regulation change
proposals for blue and flathead catfish concurrently during FY2021.
▪ Propose a minimum length limit on recreationally harvested blue catfish from
the Missouri and Mississippi rivers during FY2021
▪ Propose a minimum length limit on commercially harvested blue catfish from
the Mississippi River and possibly the St. Francis River during FY2021
▪ Recreational and commercial minimum length limits should be set at the same
level on the Mississippi River and possibly the St Francis River.
o If public sentiment is different than existing human dimensions data (e.g., anglers are
willing to sacrifice yield to improve trophy fishing potential):
▪ Develop appropriate regulation change proposals (if necessary at all) for blue
catfish and flathead catfish concurrently during FY2021.
▪ If necessary, propose regulation changes on recreationally harvested blue
catfish from the Missouri and Mississippi rivers during FY2021.
▪ If necessary, propose regulation changes on commercially harvested blue catfish
from the Mississippi River and possibly the St. Francis River.
▪ Recreational and commercial length limits should be set at the same level on
the Mississippi River and possibly the St. Francis River.
- Update Missouri’s catfish management plan and objectives by FY2023. Consideration should be
given to drafting more quantitative management objectives (e.g., catch per unit effort, size
structure, or growth rates), and objectives that outline recommendations for reevaluation of
these fisheries.