Big Indiana Bass

Melissa R. Wuellner (Melissa is a PhD student working under Dr. David Willis)
South Dakota State University

We continue to examine competition between walleye and smallmouth bass using basic approaches.  Anecdotal evidence suggests that smallmouth bass may displace walleye from rocky littoral habitats, thus forcing walleye to pelagic habitats.  In July 2008, we will begin a series of experiments that examines competition for limited habitat between walleye and smallmouth bass.  We will record habitat use and any agonistic behaviors that fish may display in defending their habitat.

We will also examine competition for food between age-1 walleye and smallmouth bass this summer.  Previous experiments showed that smallmouth bass may be the better competitor (as indexed by growth) of the two species.  However, fish were fed during daytime hours.  In the next round of experiments, we will feed fish during a period encompassing dusk, thus testing the effects of light level on food competition between walleye and smallmouth bass.

Finally, we are currently running experiments examining ontogenetic diet shifts of age-0 smallmouth bass.  We are examining growth rates and prey selectivity of four size categories (20, 40, 60, and 80 mm) of bass on three diets (zooplankton, amphipods, and larval fathead minnows).  We hope to present the results of these experiments during the upcoming 2008 Midwest Fish and Wildlife Conference.

The Natural Reproductive Cycle of Northern Largemouth Bass Micropterus salmoides salmoides in the Upper Midwest, with Applications to Out-of-season Production
Dan Spengler (M.S. student, advised by Dr. Mike Brown)

The objective of this project is to characterize the natural reproductive cycle in male and female northern largemouth bass.  Largemouth bass (five male and five female) have been collected monthly for one year (August through July 2008) from a private impoundment located approximately 9.5 miles northeast of Brookings, SD.  Blood from each bass was collected from the caudal vein and later centrifuged at 1000 x g to obtain plasma.  All plasma samples will be assayed using radio-immunoassay procedures to determine seasonal fluctuations among plasma sex steroid hormones 11-ketotestosterone, testosterone, and estradiol-17β.  Seasonal fluctuations of the egg yolk precursor protein, vitellogenin, will also be evaluated in females with ELISA analysis.  These assays will commence on 20 July.  Following blood procedures, all fish were necropsied to determine the following organosomatic indices: gonadosomatic, hepatosomatic, and visceral somatic indices, in addition to a mesenteric fat ranking.  Six gonads (three ovaries and three testes) were also taken from each monthly sample for histological processing.  These histological slides will allow us to determine ovarian and testicular maturity over a temporal regime.  In addition to these physiological parameters, key physical effects known to influence reproductive behavior (e.g. photoperiod and temperature) were monitored in situ using data loggers during the cycle.  Results from this study should be completed by fall 2008 and this information will ultimately be applied to out-of-season spawning procedures for northern largemouth bass, commencing this fall.

Evaluating smallmouth bass seasonal sampling dynamics and diets
Tom Bacula (M.S. student advised by Dr. David Willis and Dr. Brian Blackwell)

This project is over half way competed with a few more monthly electrofishing and modified-fyke net samplings to occur this year.  The preliminary results from Enemy Swim and Roy lake (completed in 2007) show that sampling in May resulted in the capture of a broad size distribution of individuals using nighttime boat electrofishing.  In the fall there was higher catch per unit effort using electrofishing, however the collection was dominated by fish shorter than stock length fish (180 mm).  The diet analysis was variable by size of individual and season, while small fish (less than 280 mm) consumed invertebrates in the spring and switched to fish in the summer and fall.  The larger fish consumed primarily crayfish across all seasons.  The results are preliminary with completion in the Spring of 2009.

Courtesy of Mike Knapp

There are several projects which are worthy of mention.  Carlson and Isermann are completing a statewide evaluation of mandatory catch and release and maximum length limits (12”) for largemouth bass that began in the mid 90’s.  They described the effects of these regulations using pre- and post-regulation data and compared these trends to similar lakes where no special regulations were in place.  They found that increased harvest regulation generally improved largemouth bass size structure, but statistically significant improvements in size structure indices were detected in only a few individual lakes.  Further, electrofishing CPUE (fish/h) of bass <15” remained unchanged while electrofishing CPUE of bass >15” generally improved, but improvements were only significant for 2 of the 3 lakes where the 12” maximum was implemented.  With the exception of one lake, increased harvest regulation did not appear to reduce growth rates.  These results suggest that despite increases in voluntary catch-and-release of largemouth bass, angler exploitation is still an important factor regulating size structure in some MN lakes and more intensive harvest regulations can improve size structure in some populations.

Radomski and Anderson finished up some of the work he was involved with using a written survey of fisheries biologists to judge the success of improving size structure of largemouth bass populations with additional harvest regulations.  Biologists were given population data from regulated and control fisheries and asked to judge whether they perceived that the population size structure had improved over time.  Based on perceptions about length frequency changes, 12 in maximum length limits and no kill regulations were about 4 times more likely to improve the size structure than just reliance on standard bag limits (the regulation on control fisheries). Improvement in size structure substantially beyond a statistically significant change was often needed before a regulation was considered successful by fisheries biologists. Also of note is that individuals differed in their propensity to see changes as improvements.

While not specifically about centrarchids, I just finished up a project evaluating fish community responses to the introduction of muskellunge across MN.  No significant decreases in mean CPUE were found among the lakes for any species after muskellunge stocking, either for the stocked lakes as a whole or within lake classes. There was a significant increase in mean CPUE for bluegill sampled by trap net over the entire group of lakes and within a single lake class, in addition to an increase in mean CPUE for black crappie sampled by gill nets in another lake class. Nevertheless, there was large variability in the changes in CPUE among lakes, and several individual lakes had significant increases or decreases in mean CPUE for some species following muskellunge stocking. The lack of consistent negative changes in mean CPUE after stocking suggests these fish species have generally coexisted well with muskellunge in these lakes at the densities that have resulted from stocking.

There are lots of interesting studies that are either underway or are being completed here in the Midwest. I'll take the next few days to highlight many of them, starting with a report from right here in Indiana:

Courtesy of Ed Braun, District 4 Fisheries Biologist

Robinson Lake is a 59 acre natural lake on the Kosiusko/Whitley County line in Northern Indiana.  It is a rather unique resource for Indiana in that there are no houses on the lake.  The majority of the shoreline is the former Crossland Scout Camp.  The only access open to the public was a private access that was not very accessible.  A general fish population survey and largemouth bass population estimate was conducted in 1993 and found an excellent bass population.  DNR (combination of Nature Preserves & DFW) purchased the property in late 1993.  DFW (Tri-County and Access North) removed all the buildings, constructed parking areas and converted the camp beach to a launch site, with no ramp.  The property was opened to the public in the summer of 1994.

In 1994, Robinson Lake was under the statewide 12-inch largemouth bass size limit and bag limit of six.  In August 1996, statewide bass size limit was increased to 14 inches and the bag limit reduced to five.  Quality bass lakes (Robinson, Tri-County FWA and Ball) were placed under an 18-inch size limit, bag limit of 2.  The Robinson Lake work plan called for bass population estimates, open water creel surveys (April through September) and general surveys in 1996, 1999, 2002, 2005 and 2208.  A creel survey was not conducted in 2005 due to budget limitations.  The goal was to maintain the existing quality bass fishery.

What Happened?

Under the 12-inch size limit, bag limit of 6, the bass population declined between 1993 and 1996.  Under the 18-inch size limit, bag limit of 2, the bass population quickly recovered.  The density of bass is well above the natural lakes average of around 20 per acre and appears to be staying at 40+ per acre.

The 1997 year class is the first one protected under the 18-inch limit throughout its life.  As these fish grew, PSD increased until this year.  RSD-18 also declined this year.  Age and growth has not been completed for 2008.  We now have an Isomet saw and associated equipment to use bony structures for age determination.  Besides scales, we collected the first 3 dorsal spines and a pectoral fin from over 150 bass this spring.  The pectoral fin rays do not appear to be useful for age determination but the dorsal rays may prove to be easier to age then scales.  The Northern Lakes Research biologist will be doing some comparison analysis.

Total fishing pressure increased from 60 h/a (1996) to 146 h/a (2002).  As of mid-July 2008, fishing pressure was 81 h/a with 2 ½ months left in the creel survey.  Fishing pressure is expected to equal the 2002 figure.

Bass anglers accounted for about ¼ of the anglers and fishing pressure in 1996.  That increased to about 40% of anglers and pressure in 2002.  That translates to an increase in bass fishing pressure from 15 h/a to 58 h/a.  While total fishing pressure increased 142% from 1996 to 2002, bass fishing pressure increased 287%.  So far this year, bass anglers have accounted for almost 50% of the anglers and fishing pressure.  Robinson Lake continues to be very popular with bass anglers.

Bass harvest in 1996 under the 12-inch limit was 206 (33 >= 18 inches).  Under the 18-inch limit, harvest declined to 22 in 1999 but increased to 31 in 2002.  So far, an estimated 24 bass have been harvested this year.  Exploitation of the stock size population (>=8 inches) declined from 17.5% in 1996 to about 1% and looks like that will not change this year.  Exploitation of 18+ inch bass declined from 38% in 1996 to 21% in 1999 and increased slightly to 23% in 2002.  That has increased to 34% already this year.

Catch and release of bass increased from 871 in 1996 to 2504 in 1999 and 2926 in 2002.  The number of bass released so far in 2008 is less then previous surveys.  199 or 7% of the bass released in 2002 were 18+ inches.  That remains unchanged.  Catch rate of bass by bass anglers went from 0.51/h in 1996 to 0.61/h in 1999 and 2002.   As of July 2008, the catch rate of bass by bass anglers has declined to 0.47/h.

The number of bluegill harvested and catch rate have declined since 1996, but the average size of bluegills harvested has increased from 6.5 in to 7.0 in 2002 and 7.5 in this year.

I came across a very good fishery research read that is published in its entirety online. Lots of interesting research papers, even if a bit dated. Use the following link to access: Warmwater Fisheries Symposium I (1991).

Key Chapters include:

• Management Opportunities and Challenges: Keys to Better Service
• Warmwater Fisheries: A Resource to be Managed
• Artificial Structures - Where They Work and How to Build Them
• Where the Fish Come From - Is the Cat out of the Bag?
• Water Level Management - Cool Management for More Fish
• Warmwater Streams - A Strong Current for Quality Management
• Non-Traditional Fishing Holes - The Old Fishing Hole Ain't What it Used To Be
• Fertilization and Forage Fish Management - Even Fish Respond to Proper Diet
• Hooking Mortality - Are We Kidding Ourselves?
• Harvest Regulations - One Is Not Enough
• Recreational Fishing - Who We Are and What We Need
• The Role of Education in Fisheries Management - We All Live Downstream