Black Bass Age Appendix (1997-2005)
Total Page：16
File Type：pdf, Size：1020Kb
WARMWATER POPULATION ASSESSMENTS IN NEW HAMPSHIRE: BLACK BASS AGE APPENDIX (1997-2005) Michael Racine Fisheries Biologist New Hampshire Fish & Game Department Region 4 Keene, NH 03431 1 INTRODUCTION Black bass (Micropterus dolomieui, smallmouth and M. salmoides, largemouth) fishery resources in the State of New Hampshire have experienced increased pressure from anglers in recent years. The New Hampshire Fish and Game Department (NHFGD) requires clubs and organizations to apply for permits to hold bass tournaments and a database which tracks these permits has shown an increase in tournament pressure over time (Gries and Racine 2006). New Hampshire’s black bass fish populations are highly utilized by anglers, with smallmouth and largemouth bass ranking among the top four species fished for by anglers (Responsive Management 2004). Additionally, the state’s bass anglers are the most satisfied; 87% of smallmouth bass anglers and 81% of largemouth bass anglers were either very or somewhat satisfied with their fishing experiences for these species. Strong support for special black bass management regulations was also shown in the survey: 70% supported catch and release; 68% supported special length limits; 50% supported reduced bag limits; and 47% supported artificial lures and flies only (Responsive Management 1996). According to the 2001 National Survey of Fishing, Hunting, and Wildlife Associated Recreation, 116,000 anglers fished 1.4 million days for warmwater species in New Hampshire (panfish: 19,000 anglers fished 316,000 days; black bass: 97,000 anglers fished 1.084 million days) (U.S. Department of Interior, Fish and Wildlife Service and U.S. Department of Commerce, U.S. Census Bureau 2003). The level of angler participation in black bass fishing represented 38% of New Hampshire’s freshwater anglers and 44% of the total days of fishing. Since the average trip expenditure for anglers fishing in New Hampshire is $24 per day, the total expenditures by anglers fishing for warmwater species equals approximately $33.6 million. As black bass populations in the state are managed solely by natural reproduction, it is necessary to collect population assessments to monitor their status in response to existing or proposed management strategies and to ensure their continued health. Additionally, age analysis allows for growth comparisons among waterbodies and aids in making appropriate management decisions. This report summarizes age analysis of black bass sampled in New Hampshire water bodies by the NHFGD from 1997 –2005. METHODS Fish Capture/Scale Collection Fish were sampled by boat electrofishing (Smith-Root SR18 and SR12) and/or by fyke nets. Fyke nets were set for at least 2 nights before retrieval and fish were processed after capture and released. Boat electrofishing was conducted after sunset using two or three netters. Electrofishing equipment was adjusted according to water conductivity and observed fish behavior relative to their position in the electrode’s field. The study design incorporated timed 2 runs using the equipment’s “on” meter time when sampling for target species (black bass or other pre-determined species) and random or community runs, to assess the other fish species in the lake. Black bass were captured during both target and community runs. All fish were placed in a live well upon capture, processed and then released. Fish were measured to the nearest millimeter, total length (TL), and weighed to the nearest gram. Scales were taken above the lateral line immediately behind the left pectoral fin (DeVries et al 1996). Scale Processing All non-regenerated black bass scales (i.e. complete and normal) were pressed on acetate slides. Each slide held images of scales from a single fish and efforts were made to fit as many scales on each slide as possible. Scale impressions were aged using a microfiche reader. Age, annuli lengths, and distance to scale edge (nearest millimeter) were recorded for each fish. Roughly one quarter of both largemouth bass and smallmouth bass were assigned a confidence rating, which acted to gauge a reader’s impression of his/her aging accuracy. They are defined as: 1 = very confident 2 = confident 3 = + 1 year 4 = + 2 years Data were imported into MS-Access where the Fraser-Lee method of back-calculation was performed on all fish 8 years old or younger and then were exported to MS-Excel. The Fraser- Lee equation is: Li = Lc –a Si + a; Sc Li = back-calculated length of the fish when the ith increment was formed, Lc = total length of the fish at capture, Sc = radius of scale at capture, Si = radius of scale at capture, a = intercept parameter. The intercept parameter (i.e. correction factor; fish length at which scales begin to form) used was 20 for largemouth bass and 35 for smallmouth bass as suggested by Carlander (1982). Data from all fish without confidence ratings and from fish with ageing confidence ratings of < 3 were used to generate average total length at age by waterbody and species. Year classes were combined due to small sample sizes. An equal weighting method was used for each mean when determining final growth rate averages. Total length versus age plots in MS-Excel used average length at age per species and plots were fitted with a logarithmic trendline. Only values for ages < 6 were used to create the trendline in order to standardize this comparison among waterbodies. The equation for this trendline was used to obtain age at quality size (11.8 inches (300 mm) for largemouth bass and 11.0 inches (280 mm) for smallmouth bass; Gablehouse 1984). 3 Corresponding growth per species was characterized as “slow”, “average” or “fast” using the 25th and 75th percentiles, as breakpoints, of age at quality size (11.8 inches (300 mm) for largemouth bass; 11.0 inches (280 mm) for smallmouth bass) from waterbodies using maximum back-calculations of fish aged to 5 and 6 years old. Age at quality size determination is of interest to fisheries managers as it is the age at which bass reach a size favorable to anglers and allows comparisons to be made among waterbodies. RESULTS Scales were aged from 2,394 largemouth bass, representing 80 water bodies, and 800 smallmouth bass, representing 28 water bodies. Back-calculated Lengths at Age of Largemouth Bass and Smallmouth Bass Mean back-calculated length at age, number of fish aged, and age at quality size varied by waterbody and species (Tables 1a. –1c., 2 and Figures 1 –108). Average maximum aged used in determining age at quality size for largemouth bass was 5.6 (SD = 0.6, n = 79) and was 5.4 (SD = 0.8, n = 25) for smallmouth bass (Figure 109 and 110). Statewide averages of back-calculated length at age (1997-2005) varied by species (Tables 3 and 4 and Figures 111 and 112). Black Bass Growth Categorization Back-calculated age at quality size and corresponding correlation coefficients of the logarithmic trendline for largemouth and smallmouth bass are presented in Tables 1a. –1c. Average age to reach quality size for largemouth bass was 3.74 (SD = 0.62, n = 79) and was 4.47 (SD = 1.66, n = 25) for smallmouth bass. All largemouth bass correlation coefficients were > 0.92 for all water bodies. Smallmouth bass correlation coefficients were > 0.90 for waterbodies having fish aged at > 4 years. The lowest correlation coefficient, 0.89 for Island Pond, only had back-calculations from age one through four. Largemouth and smallmouth bass growth categories of “slow”, “average” or “fast” are presented in Tables 5 and 6. The distribution of largemouth bass age at quality size values (n = 72 water bodies) was normal (Shapiro-Wilk W test, P = 0.28; Figure 113). The distribution of smallmouth bass age at quality size values (n = 25 waterbodies) was not normal (Shapiro-Wilk W test, P < 0.0001, Figure 114). These growth characterizations may allow for identification of waters in need of alternative management regulations. The eight waterbodies with the fastest largemouth bass growth to 300 mm in order of increasing age were Turkey Pond, Concord (2.41), Pleasant Pond, Francestown (2.60), Crystal Lake, Gilmanton (2.70), Rainbow Lake, Derry (2.72), Bolster Pond, Sullivan (2.84), Bow Lake, Strafford (2.86), Sportsman Pond, Fitzwilliam (3.01) and Pawtuckaway Lake, Nottingham (3.06). The eight waterbodies with the slowest largemouth bass growth to 300 mm in order of decreasing age were Naticook Lake, Merrimack (5.48), Sandy Pond, Richmond (5.22), Otternick Pond, Hudson (4.99), Greenwood 4 Pond, Kingston (4.98), Willand Pond, Somersworth (4.94), Crooked Pond, Loudon (4.80), Lake Potanipo, Brookline (4.79) and Little Island Pond, Pelham (4.68). The five waterbodies with the fastest smallmouth bass growth to 280 mm in order of increasing age are Clement Pond, Hopkinton (3.00), Swains Lake, Barrington (3.14), Cunningham Pond, Peterborough (3.28), Pleasant Lake, Deerfield (3.37) and Pawtuckaway Lake, Nottingham (3.38). The five waterbodies with the slowest smallmouth bass growth to 280 mm in order of decreasing age are Goose Pond, Cannan (10.77), Laurel Lake, Fitzwilliam (7.31), Skatutakee Lake, Harrisville (5.68), Highland Lake, Stoddard (5.60) and Spofford Lake, Spofford (5.41). DISCUSSION This report summarizes age analysis of black bass sampled in New Hampshire waterbodies by the NHFGD from 1997 –2005 by listing individual water body’s length at age and age at length growth categorization by species and by also creating statewide averages by species. An important implication of this report is the potential to use the growth categorization as a screening tool to identify poor or exceptional growth waters that could benefit from alternative management strategies. There may be a need to perform more in depth studies and more detailed analyses in future years, including year class comparisons.