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Old February 10th, 2005, 07:03 PM   #1
Dani
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AZ Game & Fish Tournament Mortality Study by AZGFD


Article Updated to add tournament mortality results from ABA night tournament held at Pleasant August 28th.


Background

Competitive fishing has become one of the most popular uses of freshwater fishery resources in North America over the last 30 years, especially for black bass. Nearly 25,000 certified bass tournaments are held each year on inland waters. Improved live-release practices have seemingly helped reduce the biological and sociological impacts of tournament fishing, however there is still a negative public and professional (among fisheries scientists) perception associated with competitive fishing. Even tournament participants are wary of the potential negative impacts to bass populations, particularly in the Southwest where both water and fishery resources are limited.

Initial mortality of tournament caught fish is typically recorded at weigh-in because most tournaments assess a penalty for bringing in dead fish. Advancements in fishing gear, live-wells, and weigh-in practices have helped reduce initial mortality, and tournament officials in Arizona routinely report mortality of less than 5%. However, not all released fish survive the stresses associated with capture, holding in live wells for extended periods, and weigh-in. This post-release mortality is termed delayed mortality and is rarely measured. Bass in Arizona reservoirs may be more susceptible to delayed mortality than other States because fish are taken from depths of greater than 30 feet during winter tournaments (causing an over-inflated swim bladder) and warm water temperatures during an extended summer.

Lake Pleasant

Black bass tournaments in Arizona are not regulated by the Arizona Game and Fish Department (AGFD), so there is no official record of the number of tournaments held annually. Biologists and Maricopa County Park officials estimate that there are as many 200 tournaments each year on Lake Pleasant alone. Although the economic impact of tournament fishing at Lake Pleasant is positive, biologists and anglers have expressed concern that the biological impacts may negatively impact the largemouth bass fishery. Timing of tournaments (especially during the spawn), post-release mortality due to high water temperatures, and intense fishing pressure are among the most frequently heard concerns.

AGFD Research biologists have designed a study to measure delayed mortality in five tournaments held throughout the year at Lake Pleasant. The study will not only allow us to estimate mortality caused by tournament fishing, but will also allow us to evaluate the various techniques used by tournament participants to ensure the survival of the fish that are caught. The overall goal for this research is not to restrict tournaments, rather we will make recommendations based on the results for timing of tournaments (i.e. is winter better than summer), transport of fish for off-site weigh-ins, efficient weigh-in procedures, and proper release of fish when decompression is needed (for fish taken deeper than 30-feet).


FLW – Everstart Tournament

The first tournament of the year chosen for this study was the FLW Everstart series tournament held on January 27-30, 2004.



Twenty largemouth bass were selected at random from the tournament release boat on both January 28 and January 29, 2004. On January 28, fish were weighed-in at the lake, while on January 29 fish were transported to Wal-Mart on 83rd Ave and Union Hills, approximately 15 miles from Lake Pleasant. These days were chosen for the study to assess differences in total mortality associated with the transport of fish to the Wal-Mart location. Of the twenty fish selected at random each day, ten were floating and ten were upright. Floating fish were likely unable to gain equilibrium (decompress) after being caught in deep waters and subsequent over-expansion of their swim bladders.

Twenty control fish (not subjected to angling stresses) were captured by electrofishing the shoreline on the same day tournament fish were collected. Electroshocked fish received an anal fin punch in order to differentiate them from tournament caught fish.

Ten tournament caught fish ranging from 12”–18” and ten control fish ranging from 12”–22” were placed in each of four holding pens. The rectangular holding pens measured 8 ft x 6 ft x 6ft and were floated on the water surface in a covered slip in Pleasant Harbor Marina. Bass were held in the pens for six days and monitored daily to check mortality and to remove dead fish.



FLW-Everstart Results

During the four-day tournament, 1462 largemouth bass were officially weighed-in. Initial mortality was recorded by tournament organizers and corroborated by AGFD; 19 (1.3%) were reported dead at weigh-in. Among the tournament-caught fish held in pens, only one fish died (2.5%). This fish was caught on January 28 and was weighed-in at the lake. In addition, three of the 20 tournament-caught fish with expanded swim bladders (floating) died during days two and three of the study; however, we believe that if properly decompressed, they would have survived (therefore, they were not included in mortality estimates). One control fish died from unknown causes on the fifth day of the study.

During the two days that fish were transported to Wal-Mart, initial mortality was 2.9% while non-transported fish experienced 1.1% initial mortality. The table below describes initial and delayed mortality for each day of the tournament, including control fish.



To accurately assess delayed mortality, and ultimately total mortality, there must be a correction made to account for mortality caused by holding fish in pens. In this study, mortality of control fish is attributed to being held in pens and is used to correct for delayed mortality. Therefore, the death of the tournament caught fish was negated by the death of the control fish making total delayed mortality equal to 0 and total mortality equal to 1.3%.

FLW-Everstart Summary

Total mortality (initial + delayed) of largemouth bass caught in the FLW Everstart tournament was low (1.3%) compared to other similar studies. There were likely several reasons for the low mortality. First, surface water temperatures were 56°F during the tournament, so there was no heat stress put on the fish. Second, tournament regulations were relatively stringent for holding and transporting fish (i.e. live-well standards, use of fish conditioner, no-fizz policy, efficient weigh-in procedures, specialized release boat) and likely ensured high survival rates. Finally, although fish were often taken from depths greater than 30 feet and suffered from extended swim bladders, the operators of the release boat ensured that fish were decompressed in a non-lethal manner (crating).



It appears as though transporting fish to an off-site weigh-in increased initial mortality of tournament-caught bass from 1.1% on-site to 2.9% off-site. However, only 175 fish were transported to the off-site weigh-in, so stressors to the fish were kept at minimum. If fish had been transported on the first two days of the tournament, we might have expected to see higher mortality due to crowding and other factors associated with moving large numbers of fish.


Western Outdoor News (WON) Tournament

The next tournament chosen for this study was the WON Bass tournament held on February 21-22, 2004. Thirty-six largemouth bass were selected at random from the tournament release boat on February 22, 2004. Of the 36 fish selected at random, 12 were floating and 24 were upright. Floating fish were likely unable to gain equilibrium (decompress) after being caught in deep waters and subsequent over-expansion of their swim bladders.

Thirty control fish (not subjected to angling stresses) were captured by electrofishing the shoreline on the same day that tournament fish were collected. Electroshocked fish received an anal fin punch in order to differentiate them from tournament caught fish.

Ten tournament caught fish ranging from 12”–17” and ten control fish ranging from 11”–21” were placed in each of three holding pens. Bass were held in the pens for six days and monitored daily to check mortality and to remove dead fish.

As a side-experiment, ten additional fish were “fizzed” by piercing the swim bladder, which allows for decompression. These ten fish were held in a separate pen and monitored for six days.

WON Bass Results

During the two-day tournament 895 largemouth bass were officially weighed-in. Initial mortality was recorded by tournament organizers and corroborated by AGFD; 4 (0.45%) were reported dead at weigh-in. Among the tournament-caught fish held in pens, no fish died and delayed mortality was 0.

Among the “fizzed” fish, eight fish were released with no apparent effects, the remaining 2 fish were alive, but unable to swim upright and likely perished after release

The table below describes initial and delayed mortality for each day of the tournament, including control fish.



WON Bass Summary

Total mortality (initial + delayed) of largemouth bass caught in the WON Bass tournament was low (0.45%) compared to other similar studies and lower than the Everstart tournament held in January (1.3%). Surface water temperatures were approximately 58°F during the tournament, so there was no heat stress put on the fish. Also, efficient weigh-in procedures and a specialized release boat probably contributed to the high survival rates. Finally, although fish were often taken from depths greater than 30 feet and suffered from extended swim bladders, the operators of the release boat ensured that fish were decompressed in a non-lethal manner (crating).



Although all “fizzed” fish were released, there was likely 20% mortality associated with puncturing the swim bladder. Due to the variability in the position of the swim bladder (depending on such factors as size of fish, gut fullness, sexual maturity, etc.), it is difficult for even the most experienced anglers to correctly puncture the bladder while avoiding vital organs in each individual fish. Therefore, we recommend crating the fish for decompression whenever possible.


Bill Luke Big Bass Days (BLBBD)

The third tournament chosen for this study was Bill Luke Big Bass Days (BLBBD), held on March 26-28, 2004. This tournament differs from the previous tournaments in that prizes are given each hour for the top ten bass weighed-in, regulations for live-well standards are relaxed, use of live-bait is legal, and anglers have a possession limit of one fish. The format of this tournament is “family-friendly” and typically generates a great deal of interest from amateur anglers.

To address concerns brought about by the public, we interviewed each angler as fish were weighed-in. Questions were targeted at knowledge of bed fishing (sight fishing), type of bait used, and disposition of fish upon weigh-in.

Forty largemouth bass were selected at random from the tournament release tanks on March 26, 2004. Of the 40 fish selected at random, 20 were caught by anglers using live-bait, and 20 were caught by anglers using artificial bait (to determine if there was a difference in delayed mortality among baits used).

Thirty-eight control fish (not subjected to angling stresses) were captured by electrofishing the shoreline on the same day that tournament fish were collected. Electroshocked fish received an anal fin punch in order to differentiate them from tournament caught fish.

Ten tournament caught fish ranging from 11”–21” and ten control fish ranging from 13”–19” were placed in each of four holding pens. Bass were held in the pens for six days and monitored daily to check mortality and to remove dead fish.



BLBBD Results

During the three-day tournament, 904 largemouth bass were officially weighed-in. Initial mortality was recorded by tournament organizers and corroborated by AGFD; no fish (0.00%) were reported dead at weigh-in. Among the tournament-caught fish held in pens, only one fish died (2.5%). This fish was caught using live-bait and died on the fifth day of the study. In addition, one control fish died (2.6%) from unknown causes on the sixth day of the study. The table below describes initial and delayed mortality for each day of the tournament, including control fish.



To accurately assess delayed mortality, and ultimately total mortality, there must be a correction made to account for mortality caused by holding fish in pens. In this study, mortality of control fish is attributed to being held in pens and is used to correct for delayed mortality. Therefore, the death of the tournament caught fish was negated by the death of the control fish making total delayed mortality equal to 0 and subsequently, total mortality also equal to 0 (because there was no initial mortality).

To obtain information on angler fishing habits, we conducted 892 interviews in the three day period, which accounted for 98.6 % of the fish weighed-in. Because anglers could weigh-in multiple fish, some anglers were interviewed more than once. Therefore, answers to the first question are probably only valid for the first day (because anglers were told the definition of sight fishing if it was not known). The four questions were as follows (with results):



BLBBD Summary

There were no mortalities (initial or delayed) of largemouth bass weighed-in during BLBBD. Unfortunately, like all tournaments, there is no way of determining the number of dead fish that are removed from live wells by tournament participants prior to weigh-in (to avoid penalties). However, since fish may be weighed-in every hour and dead fish are not allowed to be weighed-in, we believe that participants are likely to immediately weigh-in fish that may be in jeopardy of dying. Furthermore, we believe that mortality associated with “culling” dead fish during BLBBD is not significant.

Some anglers and other public are concerned that BLBBD may have a negative effect on the bass population because many of these fish are caught using live bait, live-wells are not regulated, and fish are sometimes caught in restricted areas of the reservoir and transported illegally to the weigh-in location. Although we found that 36% of fish were caught using live bait, our experiment shows that there was no initial or delayed mortality of fish weighed-in at BLBBD, regardless of the type of bait used. Several factors likely contributed to the low mortality rates. For example, surface water temperature was approximately 66°F, which was not warm enough to cause heat-induced stress or mortality. Also, weigh-ins were held every hour, so fish were not likely held in live-wells for long periods of time. Also, the efficient weigh-in procedures and careful release of fish (including use of fish conditioner and “crating”) likely ensured high survival rates. Finally, law enforcement officials reported no citations for illegally catching or transporting fish during the three-day tournament.

Another point of contention for concerned anglers and public is the timing of the tournament, which is typically during the spawn. The concern is that fish will either fail to spawn or lose their brood due to the displacement, which may ultimately affect bass abundance and/or quality. Our surveys show that 55% of fish were caught while the tournament angler was sight fishing. In creel surveys of the general angling public conducted during the week of the tournament, 47% of fish were caught by anglers that were sight fishing. So, the proportion of fish caught while sight fishing was similar among tournament and non-tournament anglers during the week of BLBBD. Literature (from previous studies in other states) indicates that both sight fishing (bed fishing) and displacement of fish (from tournaments) likely has little to no effect on population abundance or size structure. However, most of these studies are done on northern lakes and the true effects of sight fishing and displacement of fish in Arizona lakes will not be known until a comprehensive study can be completed.



B.A.S.S. Federation Open

The fourth tournament of the year chosen for this study was the B.A.S.S. Federation Open, held from 6 p.m. on July 10 through 6 a.m. on July 11, 2004. This report provides the preliminary results. A final report will be published when data from all tournaments has been collected (December 2004).

This tournament was a 12-hour night tournament. Due to the high water temperatures, anglers were encouraged to circulate their live wells often and use ice to keep water cool. Tournament organizers also encouraged anglers to “fizz” any fish that were caught in deep waters.

For the delayed mortality experiment, 40 largemouth bass were selected at random from the tournament release tanks on July 11, 2004. Of the 40 fish selected at random, 12 were floating and the remaining 28 were upright. Floating fish were likely unable to gain equilibrium (decompress) after being caught in deep waters and subsequent over-expansion of their swim bladders.

In addition, 24 control fish (not subjected to angling stresses) were captured by electrofishing the shoreline on the day after tournament fish were collected (electroshocking did not occur on the same day as the tournament due to equipment failure and adverse weather conditions). Due to the warm waters, collection of control fish was difficult (fish were not shallow enough to be effectively electrofished) and as a result, fish were held in the live-well longer than we had anticipated (over 1 hour). Electroshocked fish received an anal fin punch in order to differentiate them from tournament caught fish.

Ten tournament caught fish ranging from 12”–19” and 5-9 control fish ranging from 9”–19” were placed in each of four holding pens. The rectangular holding pens measured 8 ft x 6 ft x 6ft and were sunk to a depth of 20-28’ in a covered slip in Pleasant Harbor Marina. Surface water temperature was 83oF, while water temperatures at the depth of the pens ranged from 78-80oF. Bass were held in the pens for six days and monitored daily to check mortality and to remove dead fish.




B.A.S.S. Federation Open Results

For the 12-hour tournament, 163 largemouth bass were officially weighed-in. Initial mortality was recorded by tournament organizers and corroborated by AGFD; 17 fish (10.43%) were either reported dead at weigh-in or were dead prior to release. For reasons unknown to us, 7 tournament caught fish and 4 control fish escaped from the cages. They may have escaped through a small hole in the cage, which was not detected by the biologists. However, among the remaining tournament-caught fish held in pens, only two fish survived (94% mortality). In addition, all 20 remaining control fish died (100%). The table below describes initial and delayed mortality for the tournament, including control fish.



B.A.S.S. Federation Open Summary

The high mortality experienced by fish held for six days was likely a result of being confined in a relatively small area while experiencing high water temperatures, rather than actual tournament effects. The fish should have been held in cages approximately 15 feet lower in the water column, where the water temperature was about 10oF cooler. However, we were concerned that decreased oxygen below the thermocline may cause increased stress and mortality. We also wanted to hold the fish at a similar depth to where anglers were catching the fish, 20-30 feet.





Although this particular experiment did not provide the true delayed mortality estimate caused by the summer tournament, there were some interesting results to consider. For example, the 10.4% initial mortality was higher than the three previous experiments. Tournament anglers took great care in an attempt to reduce initial mortality (using ice in live-wells and recirculating water) and tournament organizers ran an efficient weigh-in (including fish holding tanks with fish conditioner), but ultimately, the length of time many of these fish spent in live-wells with the warmer temperatures caused higher initial mortality. In addition, 64% of tournament caught fish held in cages, and 45% of control fish, all died within the first two-days of the experiment. This suggests that the stress of being held in a live well, even for one-hour (control fish), may be too much for these fish to survive in warm summer temperatures.

The fact that tournament anglers caught these fish in 8-30’ of water, yet a majority of them died when held for an extended period at those depths indicates that largemouth bass likely use deeper, cooler waters, but move to more unfavorable waters (warmer) for feeding.

Tournament organizers encouraged anglers to “fizz” bloated fish to decompress air bladders. Although this is an accepted practice among anglers, we would prefer that bloated fish be decompressed by crating them to a depth at which they can release air on their own. Although there is no evidence that “fizzing” caused higher mortality rates in this tournament, results from the WON tournament suggest that crating may be a better method for decompression.



Due to questionable results of the summer B.A.S.S. Federation Open, we included a second summer tournament, the ABA Summer Nights tournament, held from 5 p.m. on August 28 through 1 a.m. on August 29, 2004. This report provides the preliminary results. A final report will be published when data from all tournaments has been collected (December 2004).

This tournament was a 6-hour night tournament. Due to the high water temperatures, anglers were encouraged to circulate their live wells often and use ice to keep water cool. Tournament organizers also encouraged anglers to “fizz” any fish that were caught in deep waters.

For the delayed mortality experiment, 30 largemouth bass were selected at random from the tournament release tanks on August 29, 2004. Of the 30 fish selected at random, all were upright, but most were lethargic and some had visible hemorrhaging around the caudal fin. Anglers were very cooperative and allowed us to measure dissolved oxygen and temperature of their live-wells at the completion of the tournament. We were able to measure water quality from 14 randomly selected live-wells.

In addition, 30 control fish (not subjected to angling stresses) were captured by electrofishing the shoreline on the night before tournament fish were collected (electroshocking did not occur on the same day as the tournament due to logistical constraints). During the previous tournament, control bass were held in a recirculating live well for a period of over one-hour. For this tournament, we reduced handling stress on largemouth bass with ice-cooled water, constant aeration, and periodic recirculation. Control fish were not held in the live well for more than 30 minutes.

Fifteen tournament caught fish ranging from 12.7”–17.9” were placed in each of two holding pens. Additionally, 15 control fish ranging from 11.7”-19.1” were placed in each of two pens. The four rectangular holding pens measured 8 ft x 6 ft x 6ft. One pen containing tournament fish and one pen containing control fish were held at the surface, the remaining two pens were submerged to a depth of 20-28’ in a covered slip in Pleasant Harbor Marina. Surface water temperature was 81.7oF, while water temperatures at the depth of the submerged pens was 80.5oF. Bass were held in the pens for five days and monitored daily to check mortality and to remove dead fish. Following the experimental period of 5 days, 10 control fish and 8 tournament fish were transported to the AGFD Fish Health Lab in Pinetop, AZ to test for virus (especially Largemouth Bass Virus), and other pathogens and parasites.


Results

Water quality in anglers’ live-wells was generally good. Dissolved oxygen of over 4.0 mg/L is adequate for fish survival; nearly 30% (4 of 14) of live-wells had DO levels below the tolerable range. Water temperatures were equal to that of lake temperatures, which was expected due to recirculation practices. Anglers using ice had only slightly lower live-well temperatures than those not using ice.



For the 6-hour tournament, 136 largemouth bass were officially weighed-in. Initial mortality was recorded by tournament organizers and corroborated by AGFD; 12 fish (8.82%) were either reported dead at weigh-in or were dead prior to release. Delayed mortality for tournament caught fish was relatively high, as 23 of the 30 (76.7%) fish died. It is interesting to note that all 15 fish held in the submerged cage died, while 8 of the fish in the surface cage died. Only four control fish died (13.3%); 3 of which where held in the surface cage and 1 in the submerged cage. Of the fish that died during the experiment, 6 tournament fish and 0 control fish died within the first 72 hours. The table below describes initial and delayed mortality for the tournament, including control fish.



To accurately assess delayed mortality, and ultimately total mortality, there must be a correction made to account for mortality caused by holding fish in
pens. In this study, mortality of control fish is attributed to being held in pens and is used to correct for delayed mortality. Therefore, when corrected for the 4 tournament fish that died, delayed mortality was 63.3% and total mortality was 66.6%.

All fish sent to the AGFD Fish lab tested negative for largemouth bass virus, bacterial infection, and external parasites.

Summary and Conclusion

During this experiment, bass were held for five days, rather than the six-day holding period used for previous tournaments at Lake Pleasant. We did this to more closely mimic summer tournament mortality studies completed in the Southeastern U.S. during 2002-2003.

The pre-release mortality experienced by fish during the ABA tournament (8.8%) was higher than during spring tournaments at Lake Pleasant, and only slightly higher than the mean initial mortality of southeastern tournaments (6.7%). Delayed and total mortality were high in this experiment (63.3% and 66.6%, respectively), but slightly lower than experienced in southeastern tournaments (74.4% and 75.9%).

We cannot explain the higher mortality experienced by tournament-caught fish held in submerged cages compared to surface cages, especially since the same pattern of mortality was not observed in control fish. Initially, we speculated that confinement and stress may be causing an outbreak of disease, possibly even Largemouth Bass Virus. However, all fish tested negative. Therefore, we believe that the total mortality of tournament-caught fish is related to the stress of tournament handling (being caught, handled, held in live-wells, carried in bags, weighed-in, and released).

Most tournament anglers took great care in an attempt to reduce initial mortality (using ice in live-wells, aeration, and recirculating water) and tournament organizers ran an efficient weigh-in (including fish holding tanks with fish conditioner, ice and aeration). This careful handling of fish is likely the reason for lower mortality rates than observed in southeastern U.S. tournaments. However, mortality rates for this, and probably other summer tournaments in Arizona are very high. Recent research by Shimano, Inc. has concluded that the stress of the weigh-in procedure may be the greatest cause of mortality for largemouth bass. Therefore, they have devised a new weigh-in system that ensures that stress in minimized during that critical period, which may be of interest to Arizona bass anglers.

Conclusions

We will reserve our final conclusions until the remaining tournaments have been completed. We would like to thank the tournament organizers and the participants for their cooperation with this study.

Last edited by Delw; February 10th, 2005 at 11:05 PM..
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