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| Conservation
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PROJECT SUMMARY FOR THE OHIO RIVER BASS STUDIES
Studies of Largemouth Bass Habitat Use, and Stocking Evaluation in the West Virginia waters of the Ohio River
06 November 2001
Prepared by: Dr. Kyle J. Hartman, Jason Freund, Eric Janney, and Elizabeth Hoffman. Wildlife & Fisheries
Resources Program, Division of Forestry, West Virginia University, 322 Percival Hall, Morgantown, WV 26506-6125.
(304) 293-2941. hartman@wvu.edu
General Introduction.
Angling for black bass is an important recreational pursuit in West Virginia. In 1991, 53% of all fishing
effort was expended in quest of black bass (U.S. Dept. of the Interior 1993). During 1992, a total of 2.5 million
angler days and 109.2 million dollars were expended on fishing related activities (USDI 1993). Assuming that black
bass anglers expended at least as much money per day as other anglers, about 57.8 million dollars per year is expended
by bass anglers towards the state's economy. As the Ohio River represents 50% of the total acreage of fishable
warm water in the state, the Ohio River bass fishery is an important recreational and economic resource to the
state. Therefore, declines in bass populations, whether real or perceived, have important social, if not biological
impacts.
Following low tournament angler catch rates in 1997 the West Virginia Division of Natural Resources, Department
of Wildlife received pressure from anglers and political leaders to improve the largemouth bass fishing in the
West Virginia waters of the Ohio River. Although there was grassroots support to initiate a stocking program for
largemouth bass in the river, the DNR resisted and decided to explore possible habitat-related limitations to largemouth
bass population sizes. Political pressure continued and by summer of 1998 the agency was forced to conduct a limited
stocking of the Ohio River. The agency did so, but insisted on an evaluation study of the stocking. Dr. Kyle Hartman
of West Virginia University was enlisted to evaluate the stocking program and to conduct a study of the habitat
use of largemouth bass in the Ohio River. This research led to the completion of three Master's Theses at WVU,
which form the basis for the following final report for these studies. The Executive Summary and final report are
organized following the specific tasks of these two Bass Studies.
Study 1. Largemouth Bass Habitat Use in the Belleville Pool of the Ohio River
Task 1. Sub-adult largemouth bass habitat use
The initial study design for sub-adult largemouth bass called for collections of young-of-year (YOY) and juvenile
bass in each of three macrohabitat types (mainstem river, embayment, and tributary habitat) to evaluate the importance
of these habitats to this life stage. A combination of electrofishing and seines were to be used to collect these
fish and compare catch per unit effort across habitats. However, seines proved impractical due to vegetation, soft
bottom, and snags, and young bass were never collected with this gear in preliminary sampling. Electrofishing CPUE
for young bass was extremely low in all habitats. This necessitated the switch in study design away from YOY in
favor of sub-adult fish that could be captured and implanted with radio tags to increase habitat observations.
Perhaps the most important finding of the study is that sub-adult largemouth bass are rare in the Ohio River, embayments,
and tributaries. Very low catch per unit effort (CPUE) in electroshocking surveys necessitated the switch to radio
telemetry because we could not gain enough observations of bass and habitat use without following tagged individuals.
This suggests young bass are either very rare or else they are in habitats in which we could not sample (e.g. too
shallow for the boat). We believe sub-adult bass abundance in the Ohio River is low because these fish do not "suddenly"
become abundant in the recreational catch or in lock rotenone surveys. A sudden abundance would suggest they are
just inaccessible to our gear. However, the data suggest that young bass are just uncommon.
Sub-adult Bass Macrohabitat Use
Sub-adult largemouth bass generally use embayment habitats in the Ohio River. This is supported by telemetry results
for 51 radio-tagged fish and electrofishing CPUE. Overall, 61% of observations with telemetry were in embayment
macrohabitats, 38% tributary and 1% main river. Electrofishing CPUE data verified the telemetry results with embayment
CPUE > tributaries except in spring. Seasonally, tributaries were most used in spring when over 70% of observations
were from tributaries and 30% were from embayments.
We were unable to assess the habitat use of juvenile largemouth bass during winter with radio telemetry due to
catchability, tag life, and surgery limitations. Due to the small size of the tag required for young fish, the
battery, and consequently tag life, was limited. This prevented us from implanting fish during summer or fall and
following movements through winter. Further, low catches of young bass in winter with electrofishing gear limited
our ability to catch fish and implant them during this period. Winter implantation was further hampered by the
fact that surgical procedures are reported to heal poorly in temperatures below 15 C resulting in mortality and
tag loss in bass (R. Pitlo, personal communication). However, despite low electrofishing success, winter habitat
use from the electrofishing surveys showed that juvenile bass used embayments in winter.
Juvenile Bass Microhabitat Use
To evaluate the microhabitat use of juvenile bass we classified the availability of microhabitat (open water, woody
debris, and vegetation) using transects in all 3 macrohabitats. After quantifying microhabitat composition and
availability in each macrohabitat we compared availability versus use of microhabitat. Analysis identified that
the "mixed" habitat type (vegetation and wood) was preferred (mixed habitat was used in a greater proportion
than it's availability) by sub-adult bass. These results suggest the limited "mixed habitat" may be a
limiting habitat type in the Ohio River. As there were no significant differences in the quantity of large woody
debris (LWD) between macrohabitats, it appears that the lack of aquatic vegetation in the mainstem river in conjunction
with the LWD, (ie. mixed type) limits habitat for sub-adult bass in the Ohio River.
Core-use areas
This study used the minimum convex polygon method to define core-use areas for sub-adult largemouth bass in the
Ohio River. Core use areas ranged from 88 - 59,400 m2. There were significant differences in core use area size
between seasons, but there was no significant relationship with bass size. Core use areas were smallest during
spring and largest during summer. Bass used between 0.2 - 89.0% of available habitat within study locations. Core
use areas of Ohio River juvenile bass were larger than those reported in the literature, suggesting poorer habitat
quality in the Ohio River than these other systems.
Management Implications
This study has shown that embayments are important to sub-adult largemouth bass and that recruitment of young bass
appears poor in the study areas. Further, size of core-use areas by sub-adult bass are extremely large compared
to other bass studies suggesting poor overall habitat quality for sub-adult bass on the river. Finally, "mixed
habitat" types are preferred and these mixes of vegetation and LWD are rare habitat types in the Ohio River.
These findings suggest that management efforts should focus on protecting embayments through easements and improvements
in basin-wide water quality through reductions in sedimentation, and perhaps herbicide use, which may limit growth
and survival of aquatic plants needed for the "mixed" microhabitat habitat type. Additional research
is needed to examine why recruitment of Ohio River largemouth bass is poor and what might be done to improve it.
Task 2. Adult Habitat Use and Movements.
Previous research has demonstrated the importance of off-channel areas as over-wintering and spawning habitats
for largemouth bass in other large river systems. However, in comparison to other large river systems, the Ohio
River has relatively little embayment and tributary surface acreage. In this study our objectives were to determine
critical over-wintering and spawning habitats of largemouth bass in the Belleville Pool of the Ohio River. To meet
our objectives we surgically implanted radio transmitters in 39 adult largemouth bass and tracked them over a 23-month
period. Main river, tributaries, and embayments comprised 84.8%, 10.2%, and 5.0% of the total surface area, respectively.
However, 17.7% and 46.8% of all estimated fish locations were in tributaries and embayments, respectively. Differences
in habitat use between main river and off-channel habitats were even more pronounced during spring and winter seasons
where off-channel habitats comprised 75.8% and 60.3% of recorded fish locations, respectively. Capture method (electroshocking
or tournament angling) may have influenced habitat use. However, even for fish released in main river habitats
following bass tournament weigh-ins, fish used main river habitats much less frequently than the availability of
that habitat would dictate. An interesting side note of this study was that for two fish we were able to document
spawning locations over two consecutive years. Each fish used the same location in both years suggesting spawning
site fidelity. The results of this study support the findings of studies on the Hudson River, Mississippi River,
and Illinois River, demonstrating the importance of off-channel habitats in the life-history of adult bass in large
river systems. Sedimentation, resulting in a loss of embayment quality and surface area, is an important problem
and thus merits increased attention. Restoration and protection efforts to improve largemouth bass fisheries in
large river systems should be concentrated in embayment habitats.
Study 2. Evaluation of a Fall Stocking of Two Sizes of Largemouth Bass In Two Ohio
River Embayments
On October 20, 1998 the West Virginia Division of Natural Resources stocked adult and intermediate size hatchery
reared largemouth bass into two Ohio River embayments in an attempt to supplement existing populations. Prior to
stocking each fish was fitted with an anchor tag and a visible implant elastomer mark to help ensure recognition
as a hatchery-origin fish. The objective of this study was to evaluate the effectiveness of this stocking event
for enhancing largemouth bass populations and improving angling opportunities in Ohio River embayment areas. Results
of other studies in rivers and reservoirs suggested that stocked bass often moved very little following stocking.
If similar results were found here it may suggest that embayments could be stocked as discrete areas to improve
angling opportunities. This was a potentially attractive management option since the Ohio River is believed to
be too large to effectively stock with bass.
A total of 4,527 bass were stocked into French Creek and Little Mill Creek. Following stocking a multifaceted sampling
approach was incorporated to: (1) evaluate the persistence and return of stocked bass to anglers' creel relative
to that of wild largemouth bass, (2) estimate fidelity of stocked largemouth bass to embayment release sites, and
(3) compare return rates and cost effectiveness of the two size classes used for stocking.
Although stocked bass comprised the majority (81%) of bass captured in electrofishing surveys conducted during
the first 30 days after stocking, the percent composition declined to 50% in January 1999, and continued to decline
at an exponential rate throughout 1999. Relative survival of the adult size class was estimated to be 2.9 times
higher than that of the intermediate class based upon returns to electrofishing gear. A total of 203 angler interviews
corresponding to 1,085 hours of angling effort were recorded during creel surveys conducted at public access landings
during which only two tagged largemouth bass were reported. Tagged fish only contributed slightly to the tournament
catch during the 2000 tournament season. Anglers weighed in 7 (1.4% of total LMB catch) tagged largemouth bass
during attended tournaments. Low return rates of stocked bass in electrofishing and angler surveys indicate that
stocked fish did not make a substantial contribution to the fishery after fall, 1998. These data suggest that fall
stocking of largemouth bass into Ohio River embayments in this manner only provided limited, short-term benefit
to the Ohio River largemouth bass fishery. Rapid loss of stocked fish in embayment areas was most likely due to
emigration of stocked fish to the Ohio River mainstem (suggested by angler tag call-in reports) and post-handling
and natural mortality over the winter of 1999. This lack of fidelity to stocking sites means the embayments cannot
be thought of as discrete areas to stock-in other words if you stock an embayment you are really stocking the whole
river.
So why not stock the whole Ohio River? Well, to maintain the fish stocking rates used in this study would require
1.67 million, 6-8 inch and an additional 0.63 million, 8-10 inch fish and cost $9 million to stock the two study
pools. Similarly, using these same values it would cost an estimated $36.5 million to stock the over 117,000 hectares
(47,000 acres) of the Ohio River bordering West Virginia - provided enough fish could be produced or purchased
to provide for these stockings. Regardless of whether the funds could be generated to do this, or whether sufficient
numbers of fish of this size could be grown, it should be stated that the stocked bass did not contribute much
to local bass tournaments. By summer 1999 many of the larger fish should have been large enough to show up in tournaments
and by summer 2000 likely all stocked bass should have attained 12 inches (the minimum size limit for tourneys).
However, in a total of 6,132 angler hours in 2000, only 7 stocked bass were weighed in at tournaments. It took
876 hours to catch a stocked largemouth bass and 9 hours to catch a wild fish. The 4,500 stocked fish contributed
only 1.4% of the catch by anglers in 2000 bass tournaments.
We conclude that embayments cannot be thought of as discrete areas to stock and that the fish stocked in 1998 contributed
little to the Ohio River fishery. Other stocking methods (other sizes or seasons) may prove more effective, but
more may be gained by learning why reproduction of wild fish appears so low.
Overall Conclusions and Management Recommendations From the Bass Studies
Several facts have emerged from the bass studies conducted by West Virginia University that may help to identify
management and research priorities for the Ohio River largemouth bass fisheries. Evaluation of macrohabitat use
by adult and sub-adult bass showed the importance of embayment, and to a lesser extent tributary habitats, to Ohio
River largemouth bass life history. Sub-adult fish used embayments extensively in all seasons except spring when
tributaries were important. Adult fish utilized these same macrohabitats, particularly during spawning season implicating
the importance of these macrohabitat types to the reproduction and recruitment of bass in the river. Sub-adult
bass also used embayments to overwinter. Thus, during many of the key life history events (spawning, nursery, and
overwintering) embayments were the most oft-used habitat. However, large core-use areas by sub-adult bass suggests
that even the better embayments (e.g. French Creek) may be of poor overall habitat quality. Microhabitat use by
sub-adult bass indicated a preference for a habitat type that was mixed including LWD and vegetation. A lack of
significant differences in LWD amounts between macrohabitats may indicate that the lack of vegetation may limit
preferred habitat of sub-adult bass.
These findings suggest that management efforts should focus on protecting embayments with easements and improvements
in basin-wide water quality through reductions in sedimentation, and perhaps herbicide use, which may limit growth
and survival of aquatic plants needed for the "mixed" microhabitat habitat type. Additional research
is needed to examine why recruitment of Ohio River largemouth bass is poor and what might be done to improve it. |
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