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Life-history Aspects of Notropis xaenocephalus (Coosa Shiner) (Actinopterygii: Cyprinidae) in Northern Georgia
Danielle M. Jolly and Steven L. Powers

Southeastern Naturalist, Volume 7, Number 3 (2008): 449–458

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2008 SOUTHEASTERN NATURALIST 7(3):449–458 Life-history Aspects of Notropis xaenocephalus (Coosa Shiner) (Actinopterygii: Cyprinidae) in Northern Georgia Danielle M. Jolly1 and Steven L. Powers1,* Abstract - The biology of Notropis xaenocephalus (Coosa Shiner) was investigated using 12 monthly collections from Moore Creek (Etowah River Drainage) in Cherokee County, GA. Specimens were collected primarily from pools with slow current and examined to determine age, growth, food habits, and reproductive cycle. The bulk of the diet consisted of Diptera adults, Chironomidae larvae, Hymenoptera, and unidentified insect parts. Feeding was greatest in the spring and lowest during winter months. Spawning occurred in spring to early summer, with 86–540 mature oocytes ranging from 0.9 to 1.3 mm in diameter present in specimens collected from March to June. Sexual maturity occurred at 1 year of age. The largest specimen collected was a female 63.8 mm SL and 4.4 g total weight. Two specimens estimated to be 38 months of age were the oldest specimens collected. As one of the most abundant minnows in the upper Alabama River Drainage, these findings provide a greater understanding of the ecology of this imperiled ecosystem. Introduction Notropis xaenocephalus (Jordan) (Coosa Shiner) was described in 1877 from specimens collected in a tributary to the Etowah River near Rome, GA (Gilbert 1998). It is a member of the N. texanus Girard (Weed Shiner) species group and appears to be sister to the widespread N. boops Gilbert (Bigeye Shiner) (Mayden 1989, Swift 1970). Notropis xaenocephalus is often abundant in small streams throughout the Coosa and Tallapoosa river drainages of northwest Georgia and northeast Alabama and is distinguished from other minnows within its range by its terminal mouth, large eye, and robust body. Little is known of the biology of N. xaenocephalus other than a spawning season from April to July as indicated by collections of tuberculate specimens during these months (Boschung and Mayden 2004). The primary objective of this study was to document selected aspects of the life history of N. xaenocephalus and briefl y compare them to those of its sister species N. boops. Study Area Fish were collected from Moore Creek upstream of its confl uence with Shoal Creek (34.3240°N, 84.5636°W), near Waleska in Cherokee County, GA (Fig.1). Moore Creek is a typical upland second-order tributary of the Etowah River between 3.1 and 6.4 m wide and less than 1.0 m deep at normal fl ows. Substrate is primarily gravel to cobble with sporadic bedrock in riffl es, gravel to sand in runs, and sand and silt in pools. Notropis xaenocephalus were collected primarily from pools with slow current. !Department of Biology, Reinhardt College, Waleska, GA 30183-2981. *Corresponding author - fishdoc.powers@gmail.com. 450 Southeastern Naturalist Vol.7, No. 3 Upstream of the study area, the Moore Creek watershed is mostly forested with moderate agricultural use and sparse residential development. Water temperatures during times of collection ranged from 5 °C in December 2004 and January to 26 °C in July 2005. Species richness of fishes within the study reach is relatively high, with 30 species collected during this study. A complete list of species collected from Moore Creek near its confl uence with Shoal Creek can be found in O’Kelley and Powers (2007). Methods Notropis xaenocephalus and vouchers of associated species were collected over a one-year period from August 2004 to July 2005 by monthly sampling near the end of each month using a 3.3-m x 1.3-m seine and a Smith-Root model 24 backpack electrofisher. A total of 305 specimens were collected, preserved in 10% formalin, rinsed with water, and transferred into 70% EtOH for long-term storage. Specimens were accessioned into the University of Alabama Ichthyological Collection (UAIC 14729-14740). Observations of behavior were conducted by snorkeling in multiple 10-minute intervals on 26 May and 28 June 2005 with qualitative descriptions of behavior noted immediately following snorkeling. Standard length (SL) of preserved N. xaenocephalus was measured using digital calipers and recorded to the nearest 0.01 mm. Sexual size dimorphism was detected using a two-sample t-test of SL; therefore, all age and growth analyses were performed separately for sexes. Specimens were blotted dry and total weight (TW), eviscerated weight (EW), and gonad weight (GW) were measured using a digital analytical balance and recorded to the nearest 0.001 g. All statistical analyses were executed using Data Desk 6.0 (Data Description, Inc., Ithaca, NY) at a significance level of alpha equal to 0.05. In reference to regressions, independent variables are listed first and dependent variables second unless otherwise noted. Figure 1. Map of Notropis xaenocephalus study area in Moore Creek (34.3240°N, 84.5636°W), near Waleska in Cherokee County, GA. 2008 D.M. Jolly and S.L. Powers 451 Standard length and EW were plotted against month. Gaps of 3 mm or more in the SL of specimens from a single month were considered indicative of different age classes (e.g., for March, all specimens were 29.52–38.06, 47.74–54.71, or 61.34–63.76 mm SL with each cluster lacking gaps approaching 3 mm). If 3 mm gaps in SL did not occur in a particular month, age classes were delineated by extrapolating lines from gaps in adjacent months. Gaps indicative of age classes appear in a frequency distribution of selected months (Fig. 2). Due to high gonadosomatic index (GSI) values found in specimens collected in April and May, we assumed spawning occurred in June for estimating age of individuals. Specimens less than 12 months of age were counted as age 0+, specimens 12–23 months were counted as age 1+, specimens 24–35 months were counted as age 2+, and specimens greater than 36 months were counted as 3+. Proportion of total specimens collected represented by each age class was calculated to approximate the age-class distribution of the population. A chi-square goodness-of-fit test of age in months was used to test differences in lifespan among sexes. Regressions by least sum of squares were performed for SL and the natural log of EW. The anterior third of the gastrointestinal track was opened and its contents were removed and weighed using a digital analytical balance and recorded to the nearest 0.001 g. Weight of gut contents for specimens with empty guts was recorded as “0.” One-way analysis of variance was performed on weight of gut contents/EW to test differences in feeding among different months. Variety of gut contents was the total number of different food items in each specimen. Regressions by least sum of squares were performed for EW and Figure 2. Frequency distribution of standard length (SL) in categories of 3 mm increments for Notropis xaenocephalus collected in August and December 2004 and March 2005 from Moore Creek. 452 Southeastern Naturalist Vol.7, No. 3 weight of gut contents as well as for EW and variety of gut contents to test infl uence of size on feeding. Food items were counted and identified to the lowest taxonomic category possible following Thorp and Covich (1991) and Merritt and Cummins (1996). Due to mastication by pharyngeal teeth, most food items were not identifiable below the level of family, order, or class. Gonadosomatic index (GSI) was calculated by dividing GW by EW. One-way analysis of variance was performed to test mean differences in GSI among months. In gravid females, greatly enlarged (≈1 mm in diameter), fully yolked, mature oocytes were counted, and five representative oocytes were measured to provide an approximation of ova size and number (see Heins and Baker 1988). Smaller oocytes (<0.5 mm in diameter) were not counted or measured. Regression of SL as a predictor of number of mature oocytes was performed to test the infl uence of size on fecundity. Results The largest specimen collected was a female 63.8 mm SL and 4.4 g TW taken in March. The smallest specimen collected was a female 25.1 mm SL and 0.26 g TW taken in September. The September collection also provided the earliest capture of young-of-the-year specimens ranging from 25.1–33.5 mm SL (mean = 30.5, SD = 2.98). For all collections, females were outnumbered by males 0.85:1. Sexual size dimorphism was detected, with mean SL for females and males 47.7 (SD = 7.18) and 44.4 (SD = 6.55) mm, respectively (P < 0.001). Due to this sexual size dimorphism, the following results are presented for females and males, respectively, unless otherwise noted. Standard length increased with age in months (R2 = 80.6%, P < 0.001; R2 = 71.8%, P < 0.001). Visual inspection of the data suggested a curvilinear relationship between SL and EW, so we log transformed EW before regressing it with SL (R2 = 96.8%, P < 0.001; R2 = 96.1%, P < 0.001). Mean SL and EW by month are presented for each sex in Figures 3 and 4. Growth rates appear to increase in spring as indicated by length and weight increases in specimens approximately 1, 2, and 3 years of age (Figs. 3 and 4). Of the 305 specimens collected, 23.9% were age 0+, 62.6% were age 1+, 12.5% were age 2+, and 1% were age 3+. Median age in months was different among sexes (P = 0.001) with the median age for males being 14 months (SD = 6.03) and for females being 19 months (SD = 7.20). Maximum age of specimens captured was 38 months and did not differ among sexes. During snorkeling, Notropis xaenocephalus were observed in pools with slow current and in the lowermost reaches of runs mostly facing upstream feeding on benthic and drifting material. They were generally located downstream of Campostoma oligolepis Hubbs and Greene (Largescale Stoneroller) and N. chrosomus (Jordan) (Rainbow Shiner), feeding in riffl es and the uppermost reaches of runs. Unidentified insect parts made up 26.7% of all food items in N. xaenocephalus examined. Diptera adults, Chironomidae larvae, and Hymenoptera (Formicidae) made up 26.3%, 19.5%, and 9.2% of all food items, respectively (Table 1). Of all specimens examined, 59% of GI tracks were empty. Feeding was not uniform across all months (F = 2.35, 2008 D.M. Jolly and S.L. Powers 453 P = 0.009) and appeared to be greatest in May, with both variety of food items (n = 7) and weight (0.005 g, SD = 0.006) of gut contents at their peaks then. Feeding appeared to decrease during July with a low mean weight of Figure 3. Standard length (SL) in mm ± one standard deviation by age in months for Notropis xaenocephalus collected from Moore Creek between August 2004 and July Figure 4. Eviscerated weight (EW) in g ± one standard deviation by age in months for Notropis xaenocephalus collected from Moore Creek between August 2004 and July 2005. 454 Southeastern Naturalist Vol.7, No. 3 gut contents (0.001 g, SD = 0.003), low total variety of food items (n = 3), and 76% of GI tracks empty. Of the specimens collected in December, 84% had empty guts, with three specimens (12%) containing detritus only, and a single specimen containing a single nematode and unidentified insect parts. A low proportion of the variation in the weight of gut contents was explained by EW (R2 = 9.3% for females and 2.9% for males), but the relationship was significant (P < 0.001 for females, P = 0.029 for males). Little of the variation in variety of gut contents was explained by EW as regressions were not significant (P = 0.196 for females, 0.0515 for males). No spawning behavior was observed during snorkeling, but mean and individual GSI peaked in spring with values greater than 0.05 only in specimens from March to June. Water temperatures during collections for these months were 11 ºC, 15 ºC, 16 ºC, and 25 ºC, respectively. The highest GSI for a single individual was 0.39 in a female measuring 51.2 mm SL from April (Fig. 5). Mean GSI was not uniform among months for females (F = 71.1, P < 0.001) or males (F = 29.1, P < 0.001) as April had the highest mean GSI for both sexes, with values of 0.288 (SD = 0.087) for females and 0.025 Table 1. Gut contents of Notropis xaenocephalus from Moore Creek by month. Numbers for each food item indicates total number of individuals for that item. Detritus and unidentified insect parts are exceptions due to the difficulty quantifying them. These two items are noted by occurrence within a single gut (e.g., the occurrence of detritus in two guts from a month is denoted as “2”). % all = percent of all contents. Month % Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total all # of specimens 26 28 25 25 25 25 25 28 25 25 25 25 307 Detritus 6 1 1 1 3 12 4.6 Nematoda 1 1 0.4 Arachnida Hydrachnida 1 1 0.4 Diplopoda 1 1 0.4 Insecta Unidentified 5 2 2 9 11 16 5 9 10 1 70 26.8 Collembola 1 1 0.4 Odonata 1 1 2 0.8 Ephemeroptera 4 1 1 6 2.3 Plecoptera 1 1 2 0.8 Hemiptera 1 1 2 0.8 Coleoptera 1 1 2 1 5 1.9 Hymenoptera 3 7 8 5 1 24 9.2 Trichoptera 1 2 1 2 6 2.3 Diptera Larvae Chironomidae 5 3 6 21 3 1 11 1 51 19.5 Simulidae 2 1 1 4 1.5 Tipulidae 1 1 0.4 Pupae 1 1 1 3 1.1 Adults 10 2 3 21 16 9 8 69 26.4 Empty 13 23 21 16 12 8 19 14 13 12 8 21 180 Items/specimen 0.81 0.36 0.24 0.72 2.32 1.68 0.56 0.68 0.48 1.32 0.92 0.20 % empty 50.0 82.1 84.0 64.0 48.0 32.0 76.0 50.0 52.0 48.0 32.0 84.0 2008 D.M. Jolly and S.L. Powers 455 (SD = 0.007) for males (Figs. 5 and 6). The lowest mean GSI values were in September for females (0.008, SD = 0.004) and November for males (0.005, SD = 0.002) (Figs. 5 and 6). Gravid females were collected from March to Figure 5. Gonadosomatic index (GSI) by month of the year (1 = January, 2 = February, etc.) for Notropis xaenocephalus females collected from Moore Creek between August 2004 and July 2005. Figure 6. Gonadosomatic index (GSI) by month of the year (1 = January, 2 = February, etc.) for Notropis xaenocephalus males collected from Moore Creek between August 2004 and July 2005. 456 Southeastern Naturalist Vol.7, No. 3 June and contained between 86–540 (mean = 256.7, SD = 108.1) mature oocytes ranging from 0.9 to 1.3 mm in diameter. Ovaries of gravid females appeared to contain a single group of mature oocytes. Standard length was not a significant predictor of number of mature oocytes in gravid females (R2 = 6.3%, P = 0.06), and the youngest specimens approaching sexual maturity appeared to be 10 months of age. Discussion Much of the biology of N. xaenocephalus appears similar to that of N. boops. The above results allow us to conclude that N. xaenocephalus live to a maximum age of approximately three years, increase feeding and growth during spring, spawn from May to June, and feed primarily on aquatic and terrestrial insects. By understanding aspects of the life history of this key component of the upper Alabama River Drainage, we are better able to understand the ecology of this imperiled ecosystem allowing for the composition and implementation of more effective conservation and management strategies. The increase in size at approximately 1, 2, and 3 years of age (Figs. 3 and 4) coincides with increases in feeding and indicates increased growth rate in the spring. The low proportion of age 2+ and 3+ specimens suggests that few individuals survive to the maximum age as is typical of most species in the N. texanus group (Boschung and Mayden 2004), and the low number of age 0+ specimens collected is likely due to the ease at which small specimens pass through the 9.5-mm mesh of the 3.3-m x 1.3-m seine. While maximum age does not appear to be different among sexes (38 months for both males and females), median age was greater for females. Only 28% of specimens greater than 24 months in age were males despite the sex ratio for all specimens collected being 0.85:1 in favor of males. This shift in sex ratio by age class is similar to that of N. rubellus (Agassiz) (Rosyface Shiner) and N. lutipinnis (Jordan and Brayton) (Yellowfin Shiner), hypothesized to be due to increased behavioral energetic costs for males increasing post-spawning mortality (Meffe et al. 1988, Reed 1955). This increase in mortality may also explain the shorter median lifespan for male N. xaenocephalus and scarcity of age 2+ males in our collections. As age estimates were based on size, an alternate hypothesis is that females grow faster than males, making them appear to be longer lived when they actually are not. This possibility is unlikely due to distinct gaps in SL by month throughout the year (Fig. 2). These gaps would be obscured if females had elevated growth rates, making it impossible to discern age groups without sex identification. Increased feeding during the spring appears to coincide with increased energetic requirements associated with gamete production, spawning, and increased growth noted earlier. The relatively even occurence of several food items in N. xaenocephalus suggests that feeding is not particularly selective (Table 1) and is in stark contrast to that of Hypentelium etowanum Jordan (Alabama Hog Sucker) within the study area. O’Kelley and Powers (2007) found that Chironomidae larvae made up 88.8% of gut contents of H. etowanum. The large proportion of gut contents of N. xaenocephalus as terrestrial insects and adult Diptera suggests many food items are picked while drifting 2008 D.M. Jolly and S.L. Powers 457 in the current. This hypothesis is also supported by our observation of N. xaenocephalus feeding on drifting items during snorkeling. The significant regression between EW and weight of gut contents may suggest that feeding increases with size. However, low R2 values suggest that any increase in feeding associated with growth is slight. Eviscerated weight also appears to be a poor predictor of variety of food items, suggesting that diet does not become more variable as individuals get larger. High GSI values in specimens collected from March to June and low values in specimens from July (Figs. 6 and 7) indicate spawning most likely occurs from May to June. A single specimen collected in August contained a single mature oocyte larger than 1 mm in diameter. This specimen only had eight identifiable mature oocytes in the ovaries and had apparently passed peak spawning condition. All specimens from fall and winter months were latent or maturing (see Heins and Machado 1993), indicating a single spring-to-early-summer spawning season. While tubercles did appear to be less conspicuous in specimens collected during the late fall and winter, tubercles were present on specimens from throughout the year. Previous reports indicate tubercles present from April to July (Boschung and Mayden 2004, Etnier and Starnes 1993), but may not have included examination of specimens from other months. The water temperatures of the spring collections for this study suggest spawning occurs in water 16–25 °C. No spawning activity was observed, but most specimens collected during months when spawning appears to occur were taken in similar habitat (slow pools) to specimens collected throughout the study. Examinations of gonads and length-frequency distributions (Fig. 2) indicated that sexual maturity occurs in the first year of age and first complete spawning season. The biology of N. xaenocephalus shares many similarities to that of its sister species N. boops. Both species appear to have similar lifespans and survival curves, as few maximum age (3+) individuals were encountered in this study and that of Lehtinen and Echelle (1979). Ova appear similar in size for both species as Lehtinen and Echelle (1979) report mature oocytes of N. boops ranging from 0.8–1.2 mm in diameter, while we observed mature oocytes from 0.9–1.3 mm in diameter in this study. Lehtinen and Echelle (1979) suggested that rapid growth occurred in N. boops from March to June and slowed through the late summer to very little growth occurring in fall and winter, similar to the pattern observed in this study. Lehtinen and Echelle (1979) also reported GSI values for N. boops began increasing in March and peaked in summer during June and July before falling to minimum levels during September. They suggested that the cool temperatures during sampling might have caused spawning to continue anomalously into July. Our data suggest a similar pattern in N. xaenocephalus as GSI increased in March, peaked in April, and was low by July, suggesting spawning occurs within a period of several weeks during spring and early summer. Both species appear to spawn in waters approaching 25 °C. In contrast to N. boops, which appear to reach sexual maturity approaching two years of age (Lehtinen and Echelle 1979), N. xaenocephalus appear to reach sexual maturity as they approach one year of age. Drifting insects at or near the surface of streams appear to be large components of the diets of both N. xaenocephalus and N. boops. The prevalance 458 Southeastern Naturalist Vol.7, No. 3 of adult Diptera in the diet may suggest that N. xaenocephalus shares the behavior of leaping from streams to capture fl ying insects as reported in N. boops by Trautman (1957). This leaping behavior was not observed during this study, leaving the possibility that adult Diptera eaten by N. xaenocephalus were drifting at the surface of the water. Acknowledgments We thank C.T. O’Kelley, C.K. Ray, and J.J. McLaughlin for assistance with field and lab work. We thank J.M. Scott, B.R. Kuhajda, and M.C. Bennett for suggestions and assistance regarding analyses and manuscript preparation. Fishes were collected under Georgia Scientific Collecting Permit number 16494 issued to S.L. Powers. This study was conducted as an undergraduate independent research project by D.M. Jolly. Literature Cited Boschung, H.T., and R.L. Mayden. 2004. Fishes of Alabama. Smithsonian Institution. Washington, DC. 736 pp. Etnier, D.A., and W.C. Starnes. 1993. The Fishes of Tennessee. University of Tennessee Press, Knoxville, TN. 681 pp. Gilbert, C.R. 1998. Type Catalogue of the Recent and Fossil North American Freshwater Fishes: Families Cyprinidae, Catostomidae, Ictaluridae, Centrarchidae, and Elassomatidae. Florida Museum of Natural History Special Publication No. 1. Gainesville, FL. 284 pp. Heins, D.C., and J.A. Baker. 1988. Egg sizes in fishes: Do mature oocytes accurately demonstrate size statistics of ripe ova? Copeia 1988(1):238–240. Heins, D.C., and M.D. Machado. 1993. Spawning season, clutch characteristics, sexual dimorphism, and sex ratio in the Redfin Darter Etheostoma whipplei. American Midland Naturalist 129(1):161–171. Lehtinen, S., and A.A. Echelle. 1979. Reproductive cycle of Notropis boops (Pisces: Cyprinidae) in Brier Creek, Marshall County, Oklahoma. American Midland Naturalist 102(2):237–243. Mayden, R.L. 1989. Phylogenetic studies of North American minnows, with emphasis on genus Cyprinella (Teleostei: Cypriniformes). Miscellaneous Publications of the University of Kansas Museum of Natural History 80:1–189. Meffe, G.K., D.L. Certain, and A.L. Sheldon. 1988. Selective mortality of postspawning Yellowfin Shiners, Notropis lutipinnis (Pisces: Cyprinidae). Copeia 1988(4):853–858. Merritt, R.W., and K.W. Cummins. 1996. An Introduction to the Aquatic Insects of North America. Third Edition. Kendall/Hunt Publishing Co., Dubuque, IA. 862 pp. O’Kelley, C.T., and S.L. Powers. 2007. Life-history aspects of Hypentelium etowanum (Alabama Hog Sucker) (Actinopterygii: Catostomidae) in Northern Georgia. Southeastern Naturalist 6(3):479–490. Reed, R.J. 1955. Phases of the life history of the Rosyface Shiner, Notropis rubellus, in Northwestern Pennsylvania. Copeia 1957(4):286–290. Swift, C.C. 1970. A review of the eastern North American cyprinid of the Notropis texanus species group (subgenus Alburnops), with a definition of the subgenus Hydrophlox, and materials for revision of the subgenus Alburnops. Ph.D. Dissertation. Florida State University, Tallahassee, FL. 515 pp. Thorp, J.H., and A.P. Covich. 1991. Ecology and Classification of North American Freshwater Invertebrates. Academic Press, Inc. San Diego, CA. 911 pp. Trautman, M.B. 1957. The Fishes of Ohio. Ohio State University Press. Columbus, OH. 683 pp.