Reproductive Behavior and Spawning Microhabitat of the Flagfin Shiner Pteronotropis signipinnis.
ABSTRACT. -- The reproductive behavior and spawning microhabitat of the flagfin shiner, Pteronotropis signipinnis, was described from aquarium observations, instream observations and microhabitat specific seining collections. Based upon aquarium observations, P. signipinnis is a broadcaster and exhibits a spawning clasp. Although spawning was never observed in nature, a high frequency of spawning related behavioral acts was observed in shallow, densely vegetated habitats ("vegetated riffles"). The spatial distribution of males and females with gonads in advanced stages of development was additional indirect evidence that vegetated riffles were an important microhabitat for reproduction. The physical characteristics of vegetated riffles may enhance the males' ability to clasp females, increase the survival of eggs and provide refuge from predation for spawning adults. Behavior related to foraging was frequently observed in "vegetated runs", indicating that P. signipinnis relies upon different habitat types to complete its life cycle and meet its resource needs.
Information on reproductive ecology is limited for many fishes including the North American cyprinid fauna (Mayden, 1991; Johnston and Page, 1992). Within the genus Pteronotropis reproductive behavior has only been published for one species, P. hubbsi (bluehead shiner) (Fletcher and Burr, 1992). Pteronotropis hubbsi is 1 of about 10 cyprinids known to spawn over centrarchid nests. Johnston and Knight (1999) examined the life history of P. welaka (bluenose shiner). Eggs and larvae were collected in sunfish nests, indicating that P. welaka is also a centrarchid nest associate.
Pteronotropis signipinnis (Bailey and Suttkus), the flagfin shiner, is a small colorful cyprinid distributed in coastal plain blackwater streams from Louisiana to Florida (Bailey and Suttkus, 1952). Baker and Ross (1981) found that P. signipinnis was strongly associated with aquatic macrophytes. Other than basic habitat requirements, littie is known of its biology (Dimmick and Lawson, 1991). I examined the reproductive ecology of P. signipinnis by qualitatively describing behavior observed in aquaria and quanitatively measuring behavioral acts in different microhabitats during instream observations. Additionally, I compared the reproductive condition of P. signipinnis collected from different microhabitats.
Aquarium observations. -- Aquarium observations were made at the University of Southern Mississippi. Specimens were collected from Parkers Greek at Hwy 13, Pearl River Go., Mississippi, on 17 April 1995. Two to four fish of unknown sex were placed into each of four 38 L aquaria containing Parkers Greek stream water, a sand-gravel substratum and a few aquatic plants (Sparganium americanum). Fish were fed a variety of foods including stream invertebrates, frozen bloodworms and flake food. Photoperiod was maintained at 14L:10D. Following seasonal changes in stream conditions, temperature was gradually raised from 17 C to 22 C during the first month of captivity and then held at 22 C ([pm]2 C).
I selected the largest fish (ca. 45 mm SL) in each aquarium for focal observations because these fish initiated most of the activities associated with spawning. Because of a lack of pronounced sexual dichromatism, it is difficult to know the sex of live Pteronotropis signipinnis. However, adult males grow larger than females so my observations were likely directed at males (Albanese, 1997). Observations were either made directly (writing notes or speaking into a microcassette recorder) or by video camera. A list of frequently observed behavioral acts possibly related to reproduction was compiled. A description of spawning behavior was prepared by integrating all observation periods.
One male and female were notable for displaying a high number of spawning-related behavioral acts in the early morning; their sex was verified through observation of egg deposition and collection of larvae. To increase the probability of observing reproductive behavior I focused many (11/24) of the observation periods on this pair of fish between 0700 and 1000. I documented male-to-male interactions by placing an additional large individual into the aquarium with this pair during one observation period.
Field, observations.--Instream behavioral observations were made in Parkers Greek near Hwy 13 between 5 June and 27 July 1996. Observations coincided with the reproductive season, which extends from April to mid-Aug. (Albanese, 1997). Five microhabitats were selected for observations: vegetated pools, vegetated riffles, vegetated runs, woody runs and sunfish nests. I selected three representative sites within each of these microhabitats and characterized their physical attributes (Albanese, 1997). Vegetated pools were deep (mean = 57 cm, range 28-103), had virtually no current (mean = 0 cm/sec, max 1), with a substratum dominated by Sparganium americanum and silt. Vegetated riffles were shallow (mean = 16 cm, range 6-32), had moderate current (mean = 7 cm/sec, range 0-25), with a complex substratum consisting of S. americanum, Orontium aquaticum, Typha spp and lots of aquatic plant detritus. Vegetated runs were of moderate depth (mean = 42 cm, range 12-58), had moderate to swift current (mean 5 cm/sec, range 0-38), with a substratum dominated by sand and S. americanum. Woody runs were moderate to deep (mean = 56 cm, range 11-92), had moderate current (mean = 6cm/sec, range 0-24), with a substratum consisting of woody debris and sand. Sunfish nests were shallow to moderate in depth (mean = 25 cm, range 8-45), had virtually no current (mean = 0 cm/sec, max 1), with a substratum consisting of gravel, silt and cobble. Woody runs were restricted to densely canopied sections of stream, whereas the vegetated microhabitats were found in open canopied areas such as bridge crossings and forest gaps (Albanese, 1997).
After delineating several representative areas within each microhabitat I randomly selected sites in which to make snorkeling observations. Observations began after I had been laying still in a microhabitat for 2 mm and lasted around 50 mm. I always positioned myself facing upstream so that any detritus stirred up would not influence the behavior of fish in the observation area. Continuous observations were made on individual focal fish from a fixed position within the site.
If a focal fish remained in my field of view for longer than 10 mm I selected a new focal fish so attributes of a single fish could not unduly influence the data. Individuals were difficult to tell apart, so it was possible that behavioral data were collected on the same fish more than once during an observation period. By observing the largest fish in my field of view ([greater than]40 mm SL) I decreased the probability of accidentally observing female behavior.
I developed an "audio snorkel" to record behavior without losing sight of focal individuals. This device consists of a Cressi-Sub SCUBA mask (covers entire face), a PVC snorkel, 5.2 m of flexible vinyl tubing (inside diameter = 0.95 cm), a microcassette recorder and a microphone with 6.1 m of wire. The audio snorkel was assembled by fitting the snorkel into the mouthpiece of the face mask, running the microphone wire through the plastic tubing (waterproofing) and inserting the recording end of the microphone into the snorkel.
Sunfish nests could not be observed underwater due to low light levels. Hosts were also very sensitive to any movement near their nests, which can be difficult to avoid while snorkeling. My procedure for observing nests was to stand motionless about 1 m from the nest and speak observations directly into a tape recorder. When possible, I would conceal myself to minimize my effect on the host or potential nest associates. Only nests that were actively maintained (i.e., swept free of fine sediments) by adult sunfish were selected for observation.
Because the number of representative sites for each microhabitat was limited, it was necessary to repeat observations within the same sites on several occasions. Thus, observation periods within microhabitats were independent in time but not always independent in space. Given large within site variation in the rate of behavioral acts, the assumption of independence was reasonably met (K. Hinkelmann, VA Tech Statistics, pers. comm.). The rate of each behavioral act was calculated by summing all occurrences of an act during an observation period and then dividing by the total observation time. The mean number of behaviors per mm was compared across microhabitats with a Kruskal-Wallis test. However, sunfish nests were excluded from these comparisons because of the rarity of Pteronotropis signipinnis in this microhabitat. Significance of these and all subsequent statistical tests was evaluated at P = 0.05.
Fish sampling in microhabitats.--Fishes were collected from each microhabitat on 13 August 1996 between 0620 and 1100. Three observation sites from each microhabitat were randomly selected and sampled with a 3.05 m X 1.22 m x 3 mm mesh seine. Following Jenkins and Burkhead (1993), three set-and-kicks, or seine hauls, were made in each site; the technique selected depended upon the physical characteristics of the sampling area. For both techniques a 1.0 [m.sup.2] area was sampled by keeping the seine poles 1.0 m apart and hauling or kicking a distance of 1.0 m. Specimens from all three hauls/kicks were combined, anesthetized with MS-222 and then fixed in 10% formalin. Ultimately, specimens were preserved in 45% isopropanol and deposited in the University of Southern Mississippi Museum of Ichthyology (USM Field No. BA96-051).
All fishes were identified and Pteronotropis signipinnis were measured to nearest 0.1 mm SL. All P signipinnis over 15 mm SL were sexed and assigned to a stage of gonadal development. Following the approach of Hems and Machado (1993), I categorized males into the following stages of testicular development: latent (LA), maturing (MA1), regular mature (MA2) or large mature (MA3). Reproductive condition in females was determined by staging ovaries according to Hems and Baker's (1993) classification system. Females were assigned to the following stages: latent (LA), early maturing (EM), late maturing (LM), mature (MA), mature ripening (MR) and ripe (RE). An approximate size at maturity was defined by the smallest male with testes in at least the MA2 stage and the smallest female with MA, MR or RE ovaries. Fish in these advanced stages of gonadal development are considered reproductive. In subsequent analyses I considered all fish above these minimum sizes as adults.
Data from fish collections were summarized for each of the five microhabitats. Length-frequency histograms were constructed using 3 mm size classes. Differences in the number of fish in advanced gonadal stages between microhabitats were evaluated with Kruskal-Wallis tests.
Aquarium observations.--A total of 873 mm of observations were made on 24 separate occasions between 11 May and 27Ju1y 1995. Observation periods ranged from 9 to 110 min and occurred between 0700 and 1900. The same pair of fish was observed spawning during five morning (0800-0900) observation periods. On four of these occasions the pair spawned more than once. The interval between spawns within the same observation period ranged from 2-40 mm. The interval between spawns during different observation periods ranged from 4-10 d. The following behavioral acts were observed:
(1) nudge--male nudges his head against females abdomen, usually near her vent
(2) quiver--male's body shudders from side to side during swimming. Quivers typically occur when the male is within 1-2 body lengths of the female
(3) attempted clasp--male attempts to curve his caudal fin around female. Typically, he will be positioned on either side or above her when executing this action
(4) clasp--male is successful at #3
(5) chase--male is swimming after female, but before making contact with her
(6) charge--male makes an accelerated thrust at another male or female. This action is similar to the chase, but differs in that swimming speed is greater and subsequent contact is not necessarily directed toward the vent
(7) parallel swim--two males swim parallel (separated by up to 4 body lengths) to each other for at least 10 cm
(8) ram--one male thrusts himself against another male during a parallel swim
(9) bite--male bites at anything in water column, on water surface or on bottom. This act is presumably related to foraging
(10) spawn--male wraps caudal fin around female's body and eggs are released
Prespawning behavior was characterized by a high frequency of chasing and nudging. The female responded by continually swimming away from the male. The male sometimes swam erratically (quivered) when he got close to the female, but this was not always distinguishable from the chase. Attempted clasps often occurred before successful spawning.
Spawning occurred when the male wrapped his caudal fin around the female's body near her anal fin. The male was positioned dorsal to the female each time this action was observed. The pair always spawned along one of the sides or within the corner of the aquarium. Eggs released during a single spawning event appeared to be released all at once and quickly sank to the bottom of the tank. On several instances the male and female quickly consumed almost all of the eggs before the eggs sank to the bottom.
Intense intrasexual interactions began within 1 mm of adding a second male to the tank containing the spawning pair of fish. The original male immediately approached and nudged the new male. Subsequently, rapid parallel swimming occurred down the long axis of the aquarium. During some of the parallel swims one male aggressively rammed himself into the other male. After 20 mm the parallel swimming stopped and one male had retreated to the corner of the tank. Males were similar in appearance so it is unknown which male was dominant in this aggressive interaction.
Field observations.--I completed 30 observation periods between 5 June and 27Ju1y 1996, totaling 1463 mm of observations. Focal individuals were only observed for 34% of this time since large males were not always in my field of view. Most observation periods (20/30) took place during the morning between 0700 and 1100. The number of observation periods and total observation time was similar in each microhabitat, averaging 6 observation periods and 300 mm (Table 1).
Active sunfish nests were usually guarded by large brilliantly colored Lepomis megalotis (longear sunfish), but one L. macrochirus (bluegill) was also observed guarding a nest. On one occasion I observed one Pteronotropis signipinnis chasing another near the water surface over a L. megalotis nest for a few seconds. In contrast, P. welaka were frequently observed entering nests. These nest entrances usually occurred when the host fled the nest area in response to my presence. Pteronotropis welaka often foraged on the nest substratum, potendaily eating eggs. Nuptial male P.welaka were also observed circling each other (head to tail) within and next to nests.
No attempted clasps, clasps or spawning events by Pteronotropis signipinnis were observed in any of the microhabitats. The mean rate of chases, nudges and rams was greatest in vegetated riffles (Table 1). The mean rate of charges and all three biting acts was greatest in vegetated runs. Vegetated pools and vegetated riffles had the highest rates of parallel swims, but this act was rare even in these habitats. With the exception of pelagic biting events, few behavioral acts were observed in woody runs. Rams was the only act that differed significantly among microhabitats (Table 1).
Behavior most similar to the spawning behavior observed in aquaria was noted during observations in vegetated riffles. Large fish (presumably males) were often observed chasing and nudging smaller fish (presumably females). These chases usually resulted in both fish leaving my field of view and entering very shallow ([less than]10 cm), densely vegetated areas. Sometimes two large fish pursued the same smaller fish. During these paired chases the large fish swam in parallel and were sometimes observed ramming each other. Two observation periods with an exceptionally high frequency of spawning-related behavioral acts occurred between 0700 and 0900. No foraging events were observed during these two periods.
Territorial behavior was observed in vegetated riffles and vegetated runs. Large focal fish were often observed maintaining a fixed position in the stream. When other Pteronotropis signipinnis approached the focal fish they were repeatedly charged, rammed or chased until they swam out of the observation area. On one occasion a focal fish and an intruding fish circled each other (head to tail). Several of the fish observed in these interactions had injuries on their dorsum that may have resulted from agonistic interactions. Many foraging events were observed in conjunction with territorial behavior, particularly in the vegetated run sites.
Fish sampling in microhabitats.--Considering collections from all microhabitats combined, Pteronotropis signipinnis, P welaka, Lythrurus roseipinnis (cherryfin shiner) and Etheostoma swami (gulf darter) were the most frequently collected species, and P signipinnis composed 74.2% of the total abundance (291 of 392 specimens). Pteronotropis signipinnis was the only cyprinid collected in vegetated riffles, and 54.3% of them were collected in this microhabitat. Many P signipinnis were also collected in vegetated pools (24.7%) and vegetated runs (17.5%), but were relatively rare in woody runs (1.7%) and nests (1.7%).
Overall, the size distribution of Pteronotropis signipinnis ranged from 9.1 mm to 52.5 mm SL (Fig. 1). The four largest fish collected were males and eight of ten fish over 45 mm were males. Vegetated pools, runs and riffles contained fishes from the entire range of sizes present in the overall collection, but a greater proportion of smaller individuals was represented in vegetated pools. Vegetated riffles contained the largest individuals and the majority of large fish. No pattern can be discerned from the few fishes collected from woody runs and nests.
Vegetated riffles contained the greatest number of fish capable of reproducing (Table 2). The majority of adult males, MA2 males, MA3 males, adult females, MA females and the only RE females were collected in this microhabitat. The number of MA3 males and RE females was significantly different between microhabitats (Table 3).
Clutch production in aquaria.--Aquarium observations substantiated that Pteronotropis signipinnis can spawn multiple clutches of eggs. The minimum interval of 4 d between spawning events that I observed indicates that P. signipinnis likely produces many clutches during their protracted spawning season. Heins and Rabito (1986) found that captive Cyprinella leedsi (bannerfin shiner) spawned clutches an average of once every 4.6 d. The length of this interval is yet to be determined in P. signipinnis because there were many opportunities for the pair to spawn without my detection. Furthermore, an artificial environment and the high quality diet I fed this pair may have resulted in the rapid development of clutches. The observation of multiple spawning events within a single observation period indicates that a clutch of eggs may not all be spawned in one discrete event, but over several events within a short time. This also agrees with Heins and Rabito's (1986) observations on Cyprinella leedsi.
Spawning microhahitat.--Behavioral observations suggest that vegetated riffles are an important microhabitat for spawning Pteronotropis signipinnis. Behavioral acts associated with reproduction (chases, nudges and rams) occurred more frequently in vegetated riffles. On average, 2.6-54X more chases and 5-14X more nudges occurred in vegetated riffles than in any of the other microhabitats; rams were observed exclusively within vegetated riffles. In addition to the observations reported here, I also observed intense spawning related behavior (chases and nudges) in a shallow vegetated area of Sweetwater Greek, Perry Co., Mississippi (Albanese, 1997).
Lack of statistical significance for chases and nudges likely reflects low sample size and high variance in these behaviors rather than support of the null hypothesis (i.e., no difference) (Peterman, 1990). While it is not possible to calculate the exact power of a Krukal-Wallis test (Mahoney and Magel, 1996), the data reported here can be used to improve the sensitivity of future research. For example, to detect the difference in the rate of chases observed in this study with reasonable power at least eight observation periods would have to be completed within each habitat type (power 0.84, pooled SD 0.632, MINITAB 12).
The reproductive condition of Pteronotropis signipinnis within vegetated riffles provides additional indirect evidence that this is an important microhabitat for spawning. Vegetated riffles contained the greatest number of males and females in advanced gonadal stages. The presence of ripe females exclusively in vegetated riffles is especially convincing. The ripe (RE) stage is the final stage of gonadal development before spawning and includes females that are actively spawning (Heins and Rabito, 1986). Only 3 of 117 adult females collected from Sweetwater Creek, Perry Co., MS, during the reproductive season were ripe, suggesting that this stage of development is brief in Pteronotropis signipinnis (Albanese, 1997). Thus my collection of 9 ripe females from vegetated riffles in Parkers Creek was exceptional. Because these females may have already begun spawning or were about to spawn, their presence in a particular area should be a strong indicator of spawning habitat.
Spawning in vegetated riffles should be adaptive for Pteronotrapis signipinnis. First, the physical characteristics of this microhabitat may facilitate clasping of females by males. In aquaria males always cornered females against structures during clasping. In addition to the observations reported here I have also observed aquarium spawning when several males chased a female into a crevice within a piece of driftwood. Substrata in vegetated riffles include dense mats of plant roots, plant detritus and stems of living plants that provide crevice-like areas where males may secure females and then spawn.
Spawning in vegetated riffles may also decrease predation on both eggs and adults. Eggs that sink into the spatially complex substratum should be concealed from predators. There should be strong selection to protect eggs from predation, as many fishes (including aquarium held Pteronotropis signipinnis) and invertebrates have been observed feeding on cyprinid eggs that were not concealed during spawning (Gale and Gale, 1977; Johnston and Kleiner, 1994; Platania and Altenbach, 1998). For adults, vegetated riffles may be an important refuge from predators. With the exception of an occasional predatory water snake (Nerodia rhombifera), no predators were observed in any of the vegetated riffles. In contrast, adult Ambloplites ariommus (shadow bass), Lepomis spp. (bluegill, longear and redspotted sunfish) and Micropterus sp (largemouth and/or spotted bass) were consistently observed in all of the other microhabitats. The apparent absence of fish predators may be related to the shallow conditions of vegetated riffl es; Ross et at. (1987) documented that many predatory species were associated with deeper habitats in a South Mississippi stream.
Agonistic interactions.--Agonistic interactions are an important part of the ecology of Pteronotropis signipinnis. These interactions are probably related to the defense of feeding territories and intrasexual competition. In vegetated runs defense of space and a high frequency of charges were associated with lots of foraging behavior, suggesting that this habitat is important for feeding.
In vegetated riffles aggressive interactions were not coupled with extensive foraging, however, it would be difficult to separate the influence of intrasexual competion and foraging behavior on the number of charges observed in this habitat. Other agonistic behavioral acts were more clearly related to spawning. Aggressive ramming during paired chases suggests that competition for females is intense. This competition may be responsible for the sexual size dimorphism observed in this species (Albanese, 1997) . Ramming during chases may improve a male's opportunity for sole access to fertilizations. C. E. Johnston (pers. comm.) also observed body contact during parallel swimming for captive P. hypselopterus (sailfin shiner) .
Reproductive behavioral strategy.--Based upon the observations of aquarium fish, Pteronotropis signipinnis can be assigned to the clasping broadcasting strategy of Johnston and Page (1992). C. E. Johnston (pers. comm.) observed similar chasing and nudging behavior in captive P. hypselopterus. Unlike studies on P. welaka and P. hubbsi, no evidence for nest association was found. However, it is possible that P. signipinnis exhibits more than one type of spawning behavior, as has been shown for other cyprinids (Johnston and Page, 1992). Further behavioral research on all five species in this genus (including P. euryzonus--broadstripe shiner) may reveal additional behavioral diversity and help clarify intrageneric evolutionary relationships.
Other cyprinids exhibit reproductive habits similar to those found in Pteronotropis signipinnis. Several species are known to broadcast their eggs in densely vegetated areas (Harrington, 1947; Mayden, 1991; Johnston and Page, 1992). Chasing and nudging have been observed in Notropis bifrenatus (bridle shiner) (Harrington, 1947) and an entire guild of pelagic spawning Great Plains minnows (Platania and Altenbach, 1998). Minnows in the genera Rhinichthys, Luxilus and Notropis have been observed driving females to the substratum during clasping (Hubbs and Walker, 1942; Raney, 1947; Johnston and Page, 1992; Johnston and Kleiner, 1994; pers. obs.).
This study presents the first reported information on the reproductive ecology of Pteronotropis signipinnis. Knowledge of such information enables natural resource managers to predict how a species will respond to natural or anthropogenic changes, thus allowing for a more proactive approach to conservation and management (Angermeier, 1995). This species uses at least two vegetated habitat types to complete its life cycle and meet its resource needs. Accordingly, practices that tend to reduce habitat heterogeneity (e.g. channelization) will impact P. signipinnis populations. While this study was hampered by statistical limitations (i.e., high variance in behavior rates and low sample size), the approach taken could add much to our knowledge of stream fish ecology and behavior in future studies. Completing observations in different habitat types may reveal unknown plasticity in reproductive behavior. In addition, the quantitative measurement of instream behavior provides a framework for comparing the importanc e of certain habitats for the persistence of stream fish populations.
Acknowledgments.--The Theodore Roosevelt Award of the American Museum of Natural History provided generous funds for travel and to build the audio snorkel. Steve Ross, F. Moore, T. Slack, D. Whitaker and K. Hinkelmann assisted me considerably with the development, execution and refinement of this project. Carol Johnston allowed me to review her notes and video of captive Pteronotropis hypselopterus. Eddy Branch assisted with the design of the audio snorkel.
(1.) Present address: Department of Fisheries and Wildlife Sciences, Virginia Tech, Blacksburg 24061. e-mail: email@example.com
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Results of Kruskal-Wallis tests for differences in the number of behavioral acts per minute exhibited by Pteronotropis signipinnis in different microhabitats. Sunfish nests were not included in comparisons because of the rarity of P. signipinnis in that microhabitat. Mean (SD) and the number of samples per microhabitat are also reported. Abbreviations are as follows: V = vegetated, W = woody, S = surface, P = pelagic and B = benthic
Behavioral act V. Pool (7) V. Riffle (6) V. Run (6) W. Run (5) Nest (6) Chases 0.16 (0.14) 1.08 (1.21) 0.41 (0.33) 0.02 (0.02) 0.00 (0.01) Charges 0.05 (0.07) 0.11 (0.12) 0.18 (0.19) 0.00 (0.01) 0.00 (0.00) Nudges 0.05 (0.08) 0.70 (0.89) 0.14 (0.17) 0.00 (0.01) 0.00 (0.00) Quivers 0.01 (0.01) 0.00 (0.01) 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) Parallels 0.07 (0.13) 0.07 (0.08) 0.00 (0.00) 0.04 (0.07) 0.00 (0.00) Rams 0.00 (0.00) 0.04 (0.05) 0.00 (0.00) 0.00 (0.00) 0.00 (0.00) S. Bites 0.01 (0.02) 0.01 (0.03) 0.04 (0.07) 0.03 (0.05) 0.00 (0.00) P. Bites 0.07 (0.07) 0.29 (0.51) 0.51 (0.70) 0.20 (0.30) 0.00 (0.00) B. Bites 0.05 (0.09) 0.02 (0.03) 0.13 (0.26) 0.00 (0.01) 0.00 (0.00) Behavioral act H statistic P value Chases 6.14 0.105 Charges 4.41 0.220 Nudges 5.17 0.160 Quivers 3.18 0.365 Parallels 5.46 0.141 Rams 9.81 0.020 [*] S. Bites 0.77 0.858 P. Bites 1.54 0.673 B. Bites 2.91 0.405 (*.)Significant at alpha = 0.05
Number collected, number of adults and number in each gonadal stage for male and female Pteronotropis signipinnis collected from different microhabitats. Fish were collected from three sites in each microhabitat. Abbreviations are as follows: LA = latent, MA1 = maturing, MA2 = regular mature, MA3 = large mature, EM = early maturing, LM = late maturing, MA = mature and RE = ripe
Males Females Habitat No. Adults LA MA1 MA2 MA3 No. Adults LA EM LM MA RE Vegetated pool 33 7 25 1 7 0 33 10 26 2 4 1 0 Vegetated riffle 67 43 22 4 36 5 76 45 49 3 8 7 9 Vegetated run 27 15 11 6 9 1 21 9 13 0 7 1 0 Woody run 2 2 0 1 1 0 3 0 3 0 0 0 0 Nest 2 2 0 0 2 0 1 1 0 0 0 1 0
Results of Kruskal-Wallis tests for differences in the number of Pteronotropis signipinnis in advanced gonadal stages between microhabitats. The mean (SD) number of fish collected from 3 sites in each microhabitat is also reported. Abbreviations are as follows: V = vegetated, W = woody, MA2 = regular mature, MA3 = large mature, MA = mature and RE = ripe
Gonadal stage V. Pool V. Riffle W. Run W. Run Nest H statistic MA2 (Males) 2.3 (2.5) 12.0 (8.2) 3.0 (4.4) 0.3 (0.6) 0.7 (1.2) 7.20 MA3 (Males) 0.0 (0.0) 1.7 (0.6) 0.3 (0.6) 0.0 (0.0) 0.0 (0.0) 11.45 MA (Females) 0.3 (0.6) 2.3 (0.6) 0.3 (0.6) 0.0 (0.0) 0.3 (0.6) 9.27 RE (Females) 0.0 (0.0) 3.0 (1.7) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 13.85 Gonadal stage P value MA2 (Males) 0.126 MA3 (Males) 0.022 [*] MA (Females) 0.055 RE (Females) 0.008 [*] (*.)Significant at alpha= 0.05
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|Publication:||The American Midland Naturalist|
|Date:||Jan 1, 2000|
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