Arizona Game and Fish Department Region VI Fisheries Program

Transcription

1 Arizona Game and Fish Department Region VI Fisheries Program Saguaro Lake Fish Survey Report April 18 th 21 st, 2016 Author: Bryant Dickens Report Date: July 7, 2016 The Arizona Game and Fish Department (AGFD) prohibits discrimination on the basis of race, color, sex, national origin, age, or disability in its programs and activities. If anyone believes that they have been discriminated against in any of the AGFD's programs or activities, including its employment practices, the individual may file a complaint alleging discrimination directly to the AGFD deputy director, 5000 W. Carefree Hwy, Phoenix, AZ 85086, (602) or U.S. Fish and Wildlife Service, 4040 N. Fairfax Dr., Suite. 130, Arlington, VA Persons with a disability may request a reasonable accommodation, such as a sign language interpreter, or this document in an alternative format, by contacting the AGFD Deputy Director, 5000 W. Carefree Hwy, Phoenix, AZ 85086, (602) Requests should be made as early as possible to allow sufficient time to arrange for accommodation.

2 Summary The Arizona Game and Fish Department conducted a fisheries survey on Saguaro Lake April 18th-21st, This study was designed to evaluate trends in fish communities and determine fish population structure over time, while continuing the standardization of statewide monitoring. The survey was comprised of 14 shoreline gill nets, set for a total of hours and 19 electrofishing sites, totaling 4.64 survey hours. A total of 509 fish were collected from gill nets representing 7 species. Electrofishing resulted in 11 species with 595 fish collected. The most abundant fish species collected from gill nets were Yellow Morone mississippiensis (64.4%) followed by Largemouth Micropterus salmoides (17.8 %). Bluegill Lepomis macrochirus (54.6%) was the most abundant species caught electrofishing, followed by Largemouth (40.5%). The reservoir currently supports a quality Largemouth fishery. Largemouth were collected during our electrofishing survey at a rate of 51.7 fish per hour. Bluegill were captured at a rate 69.8 fish per hour. Introduction Saguaro Lake is the fourth reservoir on the Salt River and is formed by the Stewart Mountain Dam (Figure 1). Saguaro Lake was formed in 1930 and is located 64 kilometers northeast of Phoenix. At full capacity, Saguaro Lake is approximately 27 kilometers long and has 35 kilometers of shoreline. The mean depth is 27 meters and has a maximum depth of 36 meters (Table 1). Water levels within this reservoir rarely fluctuate due to the large amount of water stored within the upper reservoirs. Saguaro Lake contains variety of game fish including Largemouth Micropterus salmoides and Smallmouth Micropterus dolomieu, Walleye Sander vitreus, Black Crappie Pomoxis nigromaculatus, Yellow Morone mississippiensis, Bluegill Lepomis macrochirus, Redear Sunfish L. microlophus, Green Sunfish L. cyanellus, hybrid sunfishl. spp., Channel Catfish Ictalurus punctatus, Flathead Catfish Pylodictis olivaris, Smallmouth Buffalo Ictiobus bubalus, Common Carp Cyprinus carpio, Threadfin Shad Dorosoma petenense and Tilapia Oreochromis sp. The land surrounding Saguaro Lake is managed by the Tonto National Forest and the aquatic species within the lake are managed under the Arizona Game and Fish Department (Department). A lake management plan was created in 2016 and is awaiting further review. Golden alga was first discovered in Arizona in 2005 and has since been identified in all four reservoirs along the Salt River on the Tonto National Forest. Golden alga has been documented to be the cause of several fish kills that have occurred in these reservoirs,

3 which includes Saguaro Lake. Under certain environmental stresses, golden algae produce a toxin that negatively affects gill-breathing species such as fish, mollusks, arthropods, and the gill-breathing stage of amphibians (Stewart et al. 2011). Due to the extensive fish kills in the lower three reservoirs, the Department conducted intensive fish surveys, utilizing both electrofishing and gill netting techniques in Saguaro Lake following the Department s Standard Sampling Protocol (Bryan 2004). Fish stocking coincided with these surveys between spring 2007 and spring 2009 to augment largemouth bass population. As of May 2009, the Department has stocked 36,543 (150 to 200mm) Largemouth and 255,000 (50mm) Largemouth between the three reservoirs. All stocked Largemouth were marked with either a coded wire tag (subadult) or oxytetracycline (OTC; fingerlings) chemical mark (Stewart et al. 2011). Starting January 1, 2009, there was a protective slot placed on Largemouth and Smallmouth bass within Saguaro Lake due to the substantial golden algae fish kill. The protective slot ranges were between 330 and 406 mm, with a limit of harvesting one Largemouth/Smallmouth bass within the slot and five fish outside the slot. The slot was left on for the remainder of the regulation cycle and was removed January 1, This survey was designed to evaluate trends in fish communities and determine population structure over time, while continuing the standardization of statewide monitoring. The objectives of this study were: To monitor and evaluate the fishery and fish community structure in Saguaro Lake. To detect changes over time in the fish community with priorities set for largemouth bass. To detect if Gizzard Shad Dorosoma cepedianum have dispersed downstream from Roosevelt, Apache, and Canyon lakes into Saguaro Lake and to determine their population structure if they are identified. The information obtained will aid in the development of recommendations to protect and improve the sport fishery within Saguaro Lake. Methods The survey was conducted April 18 th April 21st, A total of 19 electrofishing sites and 14 experimental gill net sites were surveyed. All electrofishing sites were sampled beginning 30 minutes past sunset and were sampled in a counterclockwise direction for at least 900 seconds. If a site was found to be unsuitable for electrofishing, it was

4 moved in a counterclockwise direction until suitable habitat was encountered and then surveyed. Fish were collected using two netters stationed on the bow of the boat. The boat used for the survey delivered electricity from an 8K watt water cooled generator through a Smith-Root model VVP-15B for an average output of 12 Amps and 120 Volts at a frequency of 60 Hz and a duty cycle of 30% Sportfish total lengths were measured to the nearest millimeter. All fish species above 100mm were also weighed to the nearest gram. The first 30 individuals of each species per site were measured and, if greater than 100mm, weighed to the nearest gram. The remaining individuals were then counted. This did not include largemouth bass, in which every individual was measured and weighed if greater than 100mm. Threadfin shad and common carp were collected, identified, and counted during the survey. Percent composition and catch per unit effort (CPUE) were calculated for all fish species in fish per hour. If more than 30 individuals were collected, standard error and 95% confidence intervals for CPUE were also calculated. Relative weight and proportional stock density (PSD) were also calculated for sportfish when more than 30 individuals were collected. Length frequency histograms were made to show distribution of year classes of species that had sample sizes of 30 fish or more. Results A total of 595 fish, comprising 11 species, were captured during the electrofishing survey on April 18 th -April 21 st, 2016, which equated to fish per hour. Species included Largemouth, Yellow, Bluegill, Green Sunfish, hybrid sunfish, Channel Catfish, Flathead Catfish, Threadfin Shad, Common Carp, Tilapia and Yellow Bullhead (Table 1). A total of 509 fish, comprising 7 species, were captured during the experimental gill net survey, which equated to 1.96 fish per hour. Species included Largemouth, Yellow, Bluegill, Channel Catfish, Flathead Catfish, Common Carp, and Tilapia, (Table 2). Sunfish (i.e. Bluegill, Green Sunfish, and Hybrid Sunfish) provide the bulk of the prey species within Saguaro Lake. Bluegill comprised 54.62% of the species observed while electrofishing, while all sunfish contributed roughly 57.65% of the electrofishing catch (Table 1). Bluegill was most common of the sunfishes, making up 54.62% of the electrofishing catch. In total, 325 Bluegill were caught electrofishing at a rate of 69.8 (SE 14.5) fish per hour (Table 1). Green Sunfish and Redear Sunfish were captured at a much lower rate and therefore condition and structural indices were not analyzed. The mean relative weight of bluegill was 95.8 for those caught by electrofishing (with 100 being considered

5 good condition), indicating a healthy overall condition for the species (Table 7). The 2016 data shows healthy reproduction of Bluegill and good distribution among size classes, with the majority of the population occurring in the mm size ranges (Figure 4). The Relative Stock Density () values are documented length groups that determine recruitment into the preferred, memorable, and trophy size ranges, while evaluating the balance of fish populations as a whole. The PSD value for Bluegill sampled was for electrofishing (Table 5). A total of 241 Largemouth were sampled during the electrofishing survey. Largemouth were caught electrofishing at a rate of 51.7 (SE 5.5) fish per hour (Table 1). The length range of Largemouth collected from both electrofishing and gill netting was mm (Figure 1). The PSD value for Largemouth sampled was for electrofishing (Table 5). The PSD-P for Largemouth was 36.28, and is currently in the range of acceptable stock density index range of There were only 6 memorable or trophy class largemouth bass captured during the electrofishing survey therefore PSD-M was relatively low at The data shows that there is currently a limited amount of growth into the memorable and trophy size classes, however, the population may continue to develop into the trophy size ranges in the future. The mean relative weight of Largemouth was (with 100 being considered good condition), for those caught by electrofishing. A total of 328 Yellow were sampled using experimental gill nets. Yellow were caught at a rate of 1.28 (SE 0.30) fish per hour (Table 2). The majority of the Yellow caught with the experimental gill nets were between mm (Figure 3). The overall mean relative weight for yellow bass captured during the gill net survey was 93.9 (Table 8). The PSD value for Yellow sampled was (Table 6). There were a total of 106 Yellow sampled that were memorable size (280 mm) or larger. A total of 51 Channel Catfish were sampled using experimental gill nets. Channel Catfish were caught at a rate of 0.19 (SE 0.056) fish per hour. The majority of the Channel Catfish caught were between 440 mm and 580 mm (Figure 4). The overall mean relative weight for Channel Catfish captured during the gill net survey was (Table 8). The PSD value for Channel Catfish sampled was 98. There were no Gizzard Shad collected in either electrofishing or gillnetting. The department will continue to monitor the spread of Gizzard Shad from the upper Salt River chain lakes. Discussion

6 Region IV personnel surveyed Saguaro Lake for changes in sportfish populations over time. We are also monitoring the potential increasing population of Gizzard Shad in Saguaro Lake by setting gill nets each survey. Gizzard Shad have not yet been identified in Saguaro Lake during a Department survey. A total of 36 were captured during the Canyon Lake survey in 2011 and 2 of those measured over 425 mm. During the 2014 survey at Canyon Lake, a total of 99 Gizzard Shad were sampled and 57 of those were over 425 mm. The population is increasing in Canyon Lake and Gizzard Shad are expected to move down into Saguaro Lake. The length range of Largemouth collected from both electrofishing and gill netting was mm (Figure 1). The PSD value for Largemouth sampled was for electrofishing. This value is currently above the recommended range of focusing on achieving large, lowdensity individuals within the Largemouth population (Gabelhouse 1984). Increased competition in similar year classes could show a reduction of prey base in the future from increased predation. The PSD value for Bluegill sampled was for electrofishing. This value is far below the recommended range of for achieving a high-density population of preferred length panfish (Gabelhouse 1984). This indicates poor recruitment of quality size bluegill. Only 25 out of the 325 sampled made it to quality length (150 mm). Saguaro Lake provides excellent fishing for Largemouth and Yellow, yet trophy size classes are lacking in both species. This could be from the lack of prey base in the reservoir. Yellow are continuing to show healthy sizes and numbers. The average size Yellow collected was 247 mm, which falls above the preferred size class of 230 mm. Threadfin Shad numbers were very low during our survey for both gill netting and electrofishing. Region IV will continue to survey Saguaro Lake in the spring every three years.

7 Literature Cited Bryan, S Standard Fish Sampling Protocol for State of Arizona Waters. Arizona Game and Fish Department. Page 133. Gabelhouse, D.W., Jr A length categorization system to assess fish stocks. North American Journal of Fisheries Management. 4: Jaeger, J Saguaro Lake 2013 Spring Survey Report. Arizona Game and Fish Department. 4-5 Stewart, W.T., A.S. Makinster, A. K. Vasey, and L.D. Avenetii Salt River Reservoir Golden Alga Project. Arizona Game and Fish Department, Research Branch, Technical Guidance Bulletin No. 13. Phoenix. 148 pp.

8 Table 1. Species composition and relative abundance (CPUE) data from electrofishing at Saguaro Lake, April Species Number Percent of Total Sampled (%) CPUE (fish/hr) Standard Error Bluegill Channel Catfish Common Carp Green Sunfish Flathead Catfish Hybrid Sunfish Largemouth Threadfin Shad Tilapia Yellow Yellow Bullhead Table 2. Species composition and relative abundance (CPUE) data from gill net sets at Saguaro Lake,April Species Number Percent of Total Sampled (%) CPUE (fish/hr) Standard Error Bluegill Channel Catfish Common Carp Flathead Catfish Largemouth Tilapia Yellow

9 Table 3. Minimum and maximum lengths and weights of fish caught during electrofishing at Saguaro Lake, April Length (mm) Weight (g) Species Min Max Mean SE Min Max Mean SE Largemouth Bluegill Table 4. Minimum and maximum lengths and weights of fish caught during gill netting at Saguaro Lake, April Length (mm) Weight (g) Species Min Max Mean SE Min Max Mean SE Largemouth Channel Catfish Yellow Table 5. Proportional stock density and incremental stock densities for fish caught electrofishing at Saguaro Lake, April Species PSD S-Q Q-P P-M M-T Largemouth Bluegill Table 6. Proportional stock density and incremental stock densities for fish caught Gill netting at Saguaro Lake, April Species PSD S-Q Q-P P-M M-T Largemouth Yellow Channel Catfish

10 Table 7. Relative weights ( ) of fish caught electrofishing at Saguaro Lake, April Species Stock Quality Preferred Memorable Largemouth Bluegill Trophy Table 8. Relative weights ( ) of fish caught gill netting at Saguaro Lake in April Species Stock Quality Preferred Memorable Trophy Largemouth Channel Catfish Yellow

11 Number of fish Sampled Length (mm) Figure 1. Size distribution of Largemouth electrofishing catch from the Saguaro Lake survey, April 2016.

12 Number of fish sampled Length (mm) Figure 2. Size distribution of Largemouth gillnetting catch from the Saguaro Lake survey, April 2016.

13 60 50 Number of fish sampled Length (mm) Figure 3. Size distribution of Bluegill electrofishing catch from the Saguaro Lake survey, April 2016.

14 Number of fish sampled Length (mm) Figure 4. Size distribution of Channel Catfish gillnetting from Saguaro Lake survey, April 2016.

15 Number of fish sampled Length (mm) Figure 5. Size distribution of Yellow gillnetting from Saguaro Lake survey, April 2016.