Gill Netting

STATUS OF LAKE POWELL SMALLMOUTH BASS

STATUS OF LAKE POWELL SMALLMOUTH BASS and BLACK CRAPPIE with reference to REGULATION CHANGES

Catch and Release - Or Keep?

My career as a biologist is unique in that I have spent my whole time on one body of water. I love Lake Powell! It is the second largest reservoir in America and has incredibly diverse fishery dynamics. There has never been time to get tired of doing the same old thing. There is new challenge each day.

I wrote this in the summer of 2001.

"Spent yesterday morning by myself in meditation concerning "my lake" and how to help it. I went to Navajo Canyon fishing for smallmouth and stripers. Found both and really enjoyed it. But my reason for being there was to finally decide what to do about the smallmouth growth slowdown. We need to harvest more fish. Most folks do not keep smallmouth. Only 5-11% of all fish caught get harvested. We have been struggling with increasing the creel limit knowing that if anglers kept 6 fish (current limit) it would help. But if we don't keep 6 fish now how will raising the limit solve the over population problem.

Obviously the question is more about education and less about numbers. So I caught and kept 6 smallmouth. Then I filleted them. It reminded me of the good old days when I filleted crappie. Fillet size and time spent was very reminiscent of crappie. But my little pile of fillets was a few short of a meal. So I caught 6 more fish and filleted them. Caught two fish better than 12 inches and released them. When I added the next batch of fillets to the pile there was just enough for a meal of real prime, thin, bite-sized, eating. Really reminded me of crappie then.

But we are talking about most visitors staying here for 3-5 days. It would be nice to have two meals when you return to CA, AZ, NV, UT or wherever. Not every one is going to keep smallmouth. The problem will still be convincing anyone to keep and fillet small fish. Those that do need to be rewarded and be able to make an impact.

So on my boat in Navajo Canyon, I decided to increase the smallmouth limit to 20 fish per day with 20 in possession. Law enforcement types do not want to separate bag and possession so I will honor their concern.

At the same time we will restrict crappie bag and possession to 10 fish to protect that population until they can find a filling reservoir condition with flooded brush which will allow them to bring off a good year class.

On January 1, 2002 a new regulation was enacted on Lake Powell that allowed anglers to keep 20 smallmouth bass. The number was not important. It could have been 10 or 30. The philosophical statement was the clincher. I wanted anglers to know that it was okay to keep a bass. Catch and release was not working at Lake Powell. Catch and keep would help improve the fishery. Anglers responded to the new keeper philosophy by doubling the bass harvest. In 2002 and 2003 about 25% of bass caught were kept.

Fast forward to 2004. After only two years of "keeping bass" the fishery has responded in dramatic fashion. Shad forage is more abundant. Smallmouth bass are bigger and fatter. Bass tournaments held in 2002 saw winning average weights of less than 5 pounds for five 12-inch smallmouth bass. The first two tournaments held in 2004 had winning weights of over 9 pounds for five fish with a "big fish" over 3 pounds. The ratio of bass over 13 inches in the population (RSD) has improved from zero in 2000 to 20% in 2003. The outlook for 2004 is for continued bass growth and better quality fishing.

How does this work? Smallmouth targeted by our catch and keep program, those 9-11 inch bass, are the most aggressive predators. Young bass are naīve, fearless and always hungry. By keeping the smaller, most aggressive bass, more food was made available for the older, wiser fish that were more selective in feeding habits. Keeping the larger bass would have had the opposite effect of leaving the most efficient predators and not freeing up enough additional forage. Anglers were given information about the goal of the bass harvest program and the target size fish to harvest. They responded with enthusiasm. This was a victory for angler education in action.

While it seems impossible for anglers to have any impact on over populated striped bass or smallmouth bass in a lake the size of Powell, the results suggest just the opposite. With over a million angler-hours expended each year, given a direction and purpose, there was enough angler impact to make a difference. By harvesting more fish, anglers played a significant role in changing the population structure of both the bass and striper populations.

The wild card is forage status. Natural cycles often determine good and bad shad production years. The bass harvest program was instituted at a time when shad numbers were low. Shad numbers improved in 2002 and 2003. There may have been improvement in bass growth without any harvest emphasis. But one thing is for sure. There were fewer mouths to feed when the shad population exploded meaning more shad for each predator. Smallmouth bass and striped bass health and growth improved in record time to levels beyond our wildest hopes.

We nailed this one perfectly! Thanks to every angler who kept a 9-inch bass from Lake Powell. Your reward awaits. Make a fishing trip here in 2004 and see what happened!

Creel limits changed in 2002.

SMALLMOUTH BASS LIMIT IS 20:

Please keep 20 bass of the most common size (9-12 inch). Release larger bass that are large enough to eat smaller bass and will help restore the proper size balance within the smallmouth population.

LARGEMOUTH BASS LIMIT IS 5:

Largemouth have declined in number due to lack of brushy cover and declined in size due to competition for forage with other game fish. Please release all largemouth which will allow these faster growing bass to represent a larger portion of the bass community.

BLACK CRAPPIE LIMIT IS 10:

Decline in flooded brush during spawning season has caused a decline in crappie numbers. The limit has been decreased to still allow some limited harvest but to protect crappie until higher lake levels cover new brush and allow crappie populations to expand.

Details of growth slowdown of smallmouth bass:

Average size of smallmouth bass in lake Powell is smaller now than it was from 1990 to 1997. Proportional Stock Density (PSD) defined in this study, as a ratio of number of smallmouth bass in the population greater than 11 inches has declined from a high of 81% in 1993 to a low of 33% in 2000. Relative Stock Density (RSD-p) which is angler preferred size fish greater than 13.7 inches has declined from 32% in 1992 to 0% in 2000.

Smallmouth are smaller in size for one or all of the following reasons:

Growth has slowed for most fish probably due to competition with each other for limited food. One year old fish caught in 1992-1995 were 8.8 inches long (11.2 inches at age 2). One year old fish caught from 1996-2000 were only 7.2 inches long (8.8 inches at age 2). Lake Powell smallmouth that once entered the "stock" (11 inches) at age 1+ now don't get that big until age 2+. Quality lengths (13.7 inches) once attained at age 3 now requires 5 years growth.

Excessively high reproduction does not appear to be driving average size down. Recent measurement of annual production by electrofishing collection has found less age 0 fish than previous surveys.

Fish physical condition (relative weight) is declining along with growth. One possible problem is the largemouth bass tapeworm which infects most of the population and has since smallmouth were introduced. While the parasite is NOT outwardly visible, and does NOT effect eating quality, it may have a negative effect on reproduction and growth. It is felt that the parasite has a compounding effect during periods of slow growth and intense competition. Parasite effect is worse when food is scarce. Crayfish are the mainstay of the diet and eating the hard shelled crayfish helps purge the adult parasite from the gut. It is only intermediate parasite life stages that live in the organs and tissues that are taxing for the fish.

Anglers at Lake Powell voluntarily released 83% of all smallmouth caught in 1997 and 89% in 2000. Over 573,000 smallmouth were caught and only 63,000 kept. Very few fish already in hand are kept due to angler philosophy, and smaller size of average fish. This voluntary return persisted even when average size of bass was larger.

DISCUSSION:

The obvious response to the problem is that there are too many smallmouth bass with not enough food. With striped bass in similar conditions we have recommended maximum angler harvest to bring predator numbers in balance with forage supplies. That seems to be exactly what is needed to meet this challenge.

Increased harvest is a good step without irreversible ramifications since it is the present nature of the angler not to keep bass. If it turned out that smallmouth populations began to plummet due to harvest and/or natural causes, we could simply say "don't keep smallmouth" and that would happen.

Increasing limits to allow a substantial harvest is a biological statement made to address the growth slow down. The bigger challenge is to educate anglers to keep smallmouth bass and particularly the 9-11 inch smallmouth bass that are so abundant. The limit increase is a message to the angling public that managing agencies recognize a problem and have assigned a regulation to address the problem realizing that a change in angler attitude will ultimate determine the success or failure of the regulation.

HISTORICAL INFORMATION BEYOND THIS POINT

Spent yesterday morning (June 2001) by myself in meditation concerning "my lake" and how to help it. I went to Navajo Canyon fishing for smallmouth and stripers. Found both and really enjoyed it.

But my reason for being there was to finally decide what to do about the smallmouth growth slowdown. We need to harvest more fish. Most folks do not keep smallmouth. Only 5-11% of all fish caught get harvested. We have been struggling with increasing the creel limit knowing that if anglers kept 6 fish (current limit) it would help. But if we don't keep 6 fish now how will raising the limit solve the over population problem.

Obviously the question is more about education and less about numbers.

So I caught and kept 6 smallmouth. Then I filleted them. It reminded me of the good old days when I filleted crappie. Fillet size and time spent was very reminiscent of crappie. But my little pile of fillets was a few short of a meal. So I caught 6 more fish and filleted them. Caught two fish better than 12 inches and released them. When I added the next batch of fillets to the pile there was just enough for a meal of real prime, thin, bite-sized, eating. Really reminded me of crappie then.

Now the public comment period begins. If you have concerns let me know. Both UT and AZ will be in the process of amending angling proclamations in the July-August time frame.

Speak up! This will be your last chance to have input on fishing rules at Lake Powell for 2002.

There are certain locations that need more "smallmouth harvest" than others. As you return from a trip think about sizes and locations. My experience at the Rincon last fall is really a main point for my decision to raise limits. We found an unending supply of 9-11 inch bass here. In one drift down the rockslide below the Rincon we caught 68 bass all just the same size. They were small and thin. The Rincon needs harvest. Please stop there and do your duty. There are other places where bass are consistently larger. Perhaps there is better balance here and not as much harvest is needed. Use discretion and selectively harvest smb from those areas that need it the most. Notice there is a better ratio of smb:lmb in the upper San Juan where more brush exists in flood plain habitat. It just proves the point that habitat will determine which fish thrive. It also follows that with limited amounts of food a certain "biomass" of fish can be produced. The Rincon can produce X amount of fish which can be more numerous and short (1000 ten inch fish); or less numerous and represented by the next size bigger bass (500 twelve inch bass). Suggest areas where we need to harvest fish (all bass less than 11 inces) and where the balance seems to be quite good (good representation of 12 inch plus bass).

Utah Division of Wildlife (Compilation and simplification of technical report)

By Georg Blommer and Wayne Gustaveson

PROBLEM:

Smallmouth are smaller in size for one or all of the following reasons:

Excessively high reproduction does not appear to be driving average size down. Recent measurement of annual production by electrofishing collection has found less age 0 fish than previous surveys.

Anglers at Lake Powell voluntarily release 83% of all smallmouth caught. Very few are kept due to angler philosophy, ethics and maybe due to smaller size of average fish. This voluntary return persisted even when average size of bass was much higher.

DISCUSSION:

The obvious response to the problem is that there are too many smallmouth bass with not enough food. With striped bass in similar conditions we have recommended maximum angler harvest to bring predator numbers in balance with forage supplies. That may be exactly what is needed to meet this challenge.

However, the lack of young fish surviving in 2000 may mean that nature is responding to take care of the oversupply of small fish. The stunting problem may be eliminated in time with no action if less smallmouth recruit to the population each year until adequate food lets them survive in larger numbers. But it is also possible that bass tapeworm has reduced fecundity to the point that smallmouth reproduction may be very low in the future despite forage conditions.

Another consideration is my feeling that all of these assumptions have been made on a relative small number of samples compared to the millions of bass in Lake Powell. We may not really know about the health and well being of the actual smallmouth population.

ACTION:

Increased harvest seems like a good step without irreversible ramifications since it is the nature of the angler not to keep bass. If it turned out that smallmouth populations began to plummet due to harvest and/or natural causes, we could simply say "don't keep smallmouth" and that would happen.

Increasing limits to allow a substantial harvest is a possibility. The bigger challenge is to get anglers to keep the current bag limit of 6 bass, especially the 9-11 inch fish. Perhaps it is not a worthy effort to increase the bag limit until it is shown that anglers are willing to catch and keep the current allowable limit.

To calm my fears that the current smallmouth bass population is not fully understood, we have made available to all interested anglers a place where total length of all fish, particularly smallmouth bass, can be entered in a data base. If the stock (11 inch) and quality (13.7 inch) population of smallmouth bass is actually larger than our data base indicates then no further action is required. If average size continues to decline then more determined action is needed.

PROCEDURE:

In the left index you will find "Report Your Catch". Here any and all fish caught can be recorded by length and weight and species. I am specifically interested in LENGTHS of smallmouth bass. If weights are recorded too that is a bonus that helps us determine relative weight (physical condition). Recording data for other species, particularly striped bass is a second priority and will be helpful.

The problem is accuracy and fidelity of data. If someone decides to enter 400 fictitious smallmouth bass in excess of 13 inches, we may make unwarranted management decisions based on erroneous data. Please participate in this action only if you are willing to record lengths and weights accurately in the field. You must write down lengths and weights of ALL BASS at the time of capture. It is just as important to record the 6 incher as it is the 15 inch bass. Do not try to remember and then guess at the end of the day or week.

I recommend that all participants in the study keep 6 smallmouth per day if they are willing to fillet and use them. Dave Fordham has included a spot for number of fish kept to track how successful an increased limit proposal may be in the future. If no one will keep fish then we will have to think of other ways to reduce numbers if that is what is needed.

If anglers can give us 5000 accurate lengths during this year that will really help to fully understand the smallmouth population and assist normal UDWR sampling which will continue to validate the data we receive on the web page.

THANK YOU.

ANNUAL GILL NETTING - LAKE POWELL - November 2000

Every November Utah Division of Wildlife biologists sample the adult game fish population by setting gill nets for two nights at each of four sampling locations on Lake Powell. The nets are set in the same places at the same time of year to reduce variability in the results. Fish numbers and species are compared over time to illustrate the trend in fish abundance.

After fish are removed from the net they are taken back to the big boat for collection of biological data. Each fish is weighed and measured. From the ratio of length to weight a physical condition index called K Factor is determined. Fish are then autopsies to determine sex, stage of maturity, stomach contents, amount of fat, and other items such as parasites or other unusual findings. Then fish are filleted so there is no waste of game fish. The remains are discarded in deep water to recycle the nutrients through fish, birds and crayfish.
Results for 2000 GOOD HOPE BAY Station

Inclement weather reduced catch. This anomaly happens every few years and is part of the long term results that must be considered before drawing conclusions. We will not make a drastic judgement that striped bass and smallmouth numbers have been dramatically reduced when it is noted that weather conditions were awful. Fish don't move much and do not get caught in stationary gill nets as often in bad weather. Numbers caught is important but must be weighed with results of other surveys to understand the real meaning of increase or decease in number of fish caught..

Most important data comes from the autopsies. We found that striped bass were in good health. That is the goal of our management program and it appears to be working. There are still many more numbers to crunch but we are extremely happy with these preliminary results.
Shad and crayfish were found in stomachs. Forage is still available for all fish. More good news.

Smallmouth bass were not sampled in large enough numbers to make any inferences about the population. Those individual fish handled were in good health but small size is still a concern. Analyzing scales for age and growth will let us understand if growth has slowed, or if good survival of young fish is the reason for so many small fish. We will work on this during the winter and come up with a plan to enhance the smallmouth population.

The net survey always produces some surprises. We caught a kokanee salmon adult at Rincon the day after the Good Hope survey. This is the second occurrence of kokanee (!987) in the survey. There is not much likelihood that a population will ever establish. An occasional lake trout and rainbow and brown are caught but these fish do not have prime spawning conditions here and are not expected to establish a viable population.
Walleye are found in modest numbers. They are real predators and often eat other game fish. Stomachs of stripers always contain shad, crayfish or plankton. Stripers do not eat other bass or sunfish except on very rare occasions.

Return to the Lake Powell Home Page

Return to Widlife Resources Home Page