 |
| FishTails |
Bass Heading Home
The final chapter
[August 25, 2004]
As all of you well know, ecological issues surrounding bass tournaments focus largely on the fate of displaced
fish, whether defined in terms of mortality or a return to previously held home ranges. Although, we as a Federation,
have increased our focus on mortality and displacement issues relating to our tournaments, the attitude of non-tournament
anglers remains skeptical, with respect to the survival chances of tournament caught fish. A recent summary of
mortality in black bass tournaments has shown a reduction in mortality over the last thirty years, with the implementation
of better handling procedures and guidelines for anglers as well as tournament organizers to follow to help insure
the release of as many tournament caught bass a possible. Despite increased attention, however, the interaction
between water temperature and handling procedures continues to be a persistent challenge in reducing tournament
related mortality. This challenge seems to stem from the exponential relationship between water temperature and
mortality in tournaments. It has also been thought by some that since tournaments are held in locations with very
high summer temperatures, the temperature mortality relationship may represent a barrier through which current
tournament practices cannot significantly improve survival. Displacement in bass tournaments occurs following handling,
when fish are not returned to sites of capture, also there appears to be differences in return rates between smallmouth
bass and largemouth bass in biotelemetry studies that displace fish. In a 1996 study, in Ontario Canada, 15 out
of 18 or 83% of the displaced smallmouth bass fitted with ultrasonic transmitters, returned to previously held
home ranges. In New York, the average percent return of largemouth bass to capture sites in three tournament locations
was 26%. In the upper Chesapeake Bay region, 43 per cent and 33 percent of displaced largemouth bass returned to
the Susquehanna and Northeast Rivers, respectively, after displacement. Mortality in bass tournaments occurs following
handling (initial mortality) and after fish are returned to the water (delayed mortality). The survival of bass
continues with the dominating question of the fate of tournament caught fish and what we as Federation members
can do to insure an increase in survival rates of the black bass we love and enjoy so much.
The objective of Mr. Ridgway's study is to determine the effects of displacement on the movements, home range,
and survival of largemouth bass fitted with radio and ultrasonic tags in a northern lake. Largemouth bass were
displaced in a tournament fashion to determine if they returned to previously held home ranges. Survival was established
over the summer and fall following displacement, using the disappearance of radio tags as a means of calculating
seasonal patterns of survival. Data was collected on the movement of 55 largemouth bass from early June through
October in 1996,1997, and 1998 in Rideau Lake in eastern Ontario. The lake is 14,236 acres and has an average depth
of 43.6 feet, also the lake contains both cold water fish community and a warm water fish community. In this study,
efforts were largely restricted to the sallow warm water areas of the lake, because competitive tournaments focusing
on bass occur in the summer months. Movements and home range area were determined for a set of reference fish,
for the purpose of comparison to displaced fish, data from nondisplaced largemouth bass were collected in the year
preceding (1996) and following (1998) the displacement experiment (1997) in large part because of the logistical
difficulty in targeting and capturing specific fish. So the data on movements and home range from nondisplaced
largemouth bass were used in comparison with displaced largemouth bass. In the third week of June 1997, 27 largemouth
bass from a variety of locations in Rideau Lake were captured by a group of volunteer anglers, then surgically
implanted with radio tags, and displaced to predetermined locations. Angler's marked capture and release locations
on maps. They were assigned predetermined release locations (bays and points of land) to ensure a range in displacement
distances. Exact locations of release within predetermined sites were left to the discretion of the anglers. Data
collected in 1996 and 1998 indicated that largemouth bass remained in restricted home ranges into the fall of each
year. This information on movements in an undisturbed state (1996 and 1998) was used in 1997 to assign the capture
location of largemouth bass as being within their home range. Thirteen displaced largemouth bass had sufficient
data to calculate home range. The sixteen-week period from 29 June 1997 to 18 October 1997 was divided into eight,
two week long periods. The potential disappearance of the 27 displaced largemouth bass implanted with radio tags,
in each of the eight time periods, was used to determine seasonal patterns of survival of this group of fish. First,
6 of the 27 bass were caught and kept by anglers based on a return of the radio tag or information provided by
anglers and observers (four fish) of by locating the bass in a holding tank (one fish) or on a stringer (one fish).
Second, 4 of the 27 bass disappeared in midsummer after following their movements and fixing their locations continuously
for a number of weeks. This kind of disappearance was unusual since all non-displaced bass (1996 and 1998) had
never made moves of a magnitude that could lead to a disappearance. When these fish disappeared, lake-wide searches
were undertaken repeatedly in an attempt to locate the messing fish. Searches included capture sites and all possible
routes of return from release sites. Searches also included areas of the lake beyond the limits of the displacement
experiment. It was concluded that, these fish were either captured by an angler or died and settled into deeper
areas of the lake that were inaccessible for detection using radio technology. The results of Mr. Ridgway's study
address two important questions concerning the fate of largemouth bass displaced in a tournament fashion: First,
most largemouth bass displaced in this study did not return to areas of initial capture. Only fish within 4.9 miles
of their original capture site returned (7 out of 15 bass displaced within 4.9 miles) with three fish not returning
until the following spring. Overall, 37 percent of displaced largemouth bass in this study returned to original
capture areas. Second, this study provided a survival estimate of largemouth bass following displacement that represented
the duration of the fishing season. Incorporating natural mortality, based on an earlier tagging study of a sanctuary
population of largemouth bass, the annual estimate of survival in this study is higher than an estimate from 1981
in Rideau Lake. There also appear to be clear differences between largemouth and smallmouth bass in their movements.
In an earlier study, a high percentage of smallmouth bass returned to previously held home ranges when displaced
over a range of distances used in the study. With the exception of two largemouth bass that returned 11.2 miles
to capture sites in the New York study, data from Ontario and New York indicate that few if any, fish return from
displacement greater than 4.9 miles from the site of original capture.
The apparent reduction in fishing mortality observed in this study relative to samples in 1981, may be due to a
number of factors. Certainly different gear types can sample different size distributions of a fish population
that in turn can lead to different estimates of population parameters. A more likely interpretation of the decline
in fishing mortality is the current prevalence of catch- and -release practices relative to twenty years ago. An
important component of catch-and-release seems to be an increased interest in minimizing stress in fish, among
most bass anglers and angling associations such as BASS and the BASS Federations. In this study, volunteer bass
anglers displaced the fish to pre-selected sites for release, although the exact location of release in these sites
was left to the discretion of the anglers. Largemouth bass were kept in livewells and transported following normal
handling procedures. Based on the estimate of survival from radio-tagged bass and the role of volunteer anglers
in this study, it is possible to achieve minimal effects of tournaments on the survival of largemouth bass over
the course of a fishing season.
These conclusions must come with details to be considered when evaluating the study to prevent mis-interputation.
First, this study displaced single fish and not large groups of bass that normally occur in most post tournament
releases. In the latter case, many fish are typically released in relatively few locations so post release movements
away from these sites may differ from what was observed in the Rideau Lake study. Furthermore, because multiple
tournaments can occur on a lake, these releases can occur multiple times in a fishing season although not necessarily
at the same location each time. Second, this study occurred near the northern distribution of largemouth bass where
relatively moderate water temperatures are known to be beneficial for survival in the short term. The density of
released largemouth bass and the frequency of tournaments on a water body under normal tournament scenarios, as
well as the generally sub-lethal water temperatures that occur in northern sites, are important considerations
when interpreting the results of this study. The effects of multiple captures and repeatedly releasing high densities
of bass in limited locations are important issues for future work. For example, the vulnerability of largemouth
bass to angling when released in large groups may differ from what was occurring in the Rideau Lake study where
individual fish were released at different sites. Increasing or decreasing catchability will have a direct effect
on survival estimate. The improvement in survival in 1997 relative to 1981 was also evident in the estimate of
annual survival based on the age distribution of radio-tagged bass. Indeed, the estimates of annual survival in
1997 utilizing two different methods were closely matched. A full examination of the effects of tournament handling
on survival of bass would require tracking the fates of individuals in two groups of radio-tagged bass, one handled
in tournament fashion and the other released at site of capture, to tease apart any possible effects of tournaments
on seasonal survival. Despite a sharper focus on the operation of mortality in bass tournaments, there is clearly
a need to continue to investigate the survival of bass caught in tournaments in a variety of formats. The most
important need may be to repeat this season-long approach at other sites where the fates of displaced fish are
followed for many weeks.
The West Virginia BASS Federation has worked the last few years on new ways to handle tournament caught bass and
our release procedures. We have oxygen pumps and a bottle of oxygen with a diffuser system hooked to our holding
tank and an oxygen pump hooked to our tubs to put oxygen on your fish while waiting line to get weighed in. Some
people think we are being to controlling by saying we will not weigh fish in any other weigh in bags but ours.
This is our way of insuring there are not to many fish waiting in bags without oxygen on them and to insure the
survival of the fish. We give out ten bags at a time and that is all. We do the Bass Festival with ten bags and
150 boats and have an outstanding record of live release and have been praised by the WVDNR for our efforts and
even have the Ohio River biologist Chris O'Bara assisting with the release. The Federation also does not have any
mid-summer tournaments, which also helps with our 97 percent release rates from year to year. May God Bless You
All and keep you and your families safe throughout the year.
Sincerely, Jim |
|
|
|
