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Notice: ©1990 Elsevier Inc. The final published version of this manuscript is available at http://www.sciencedirect.com/science/journal/03009629 and may be cited as: Peterson, M. S. (1990). Hypoxia-induced physiological changes in two mangrove swamp fishes: sheepshead minnow, Cyprinodon variegatus Lacepede and sailfin molly, Poecilia latipinna (Lesueur). Comparative Biochemistry and Physiology Part A: Physiology, 97(1), 17-21.doi:10.1016/0300-9629(90)90715-5

HYPOXIA-INDUCED PHYSIOLOGICAL CHANGES IN TWO MANGROVE SWAMP FISHES: SHEEPSHEAD MINNOW, CYPRINODON VARIEGATUS LACEPEDE AND SAILFIN MOLLY, POECILIA LATIPINNA (LESUEUR)

MARK S. PETERSON* Harbor Branch Oceanographic Institution, Inc. Division of Marine Science 5600 Old Dixie Highway Ft. Pierce, FL 34946, USA. Telephone: (601) 325-3120

(Received 19 December 1989)

Abstract-I. Laboratory measurements (30°C and 300/00 salinity) were made of plasma osmolality, plasma chloride ion concentration, hematocrit, oxygen consumption and survival of sheepshead minnow, • Cyprinodon oariegatus Lacepede and sailfin molly, Poecilia latipinna (Lesueur) under normoxic (150 mm Hg) and hypoxic (40 mm Hg) conditions. 2. Significant increases in hematocrit and reductions in oxygen consumption were documented for both species. Plasma osmolality increased in sheepshead minnows while in hypoxic conditions but plasma

" chloride did not change from values in 150mm Hg in either species. There was no mortality in either species during the 24 hr hypoxia survival tests. 3. Results suggest a strong tolerance of hypoxia in both species and use of aquatic surface respiration (ASR) by P. latipinna. 4. Low-level mortality occurs in both species but severe mortality occurs only in C. tariegatus and may be due to synergistic environmental effects typical of mangrove swamp habitats.

INTRODUCTION molality, plasma chloride ion concentration and oxy Mangrove swamps provide critical habitats for nu gen consumption. Finally, I investigated survival in merous resident and transient fishes (Odum et al., low-oxygen tensions in these two resident species. 1982; Thayer et aI., 1987). These habitats, however, are being modified for mosquito control or waterfowl MATERIALS AND METHODS management in a number of southeastern USA estu Field collections and general laboratory protocol aries (Whitman and Meredith, 1987) with resulting Fishes were collected from impounded mangrove swamps water quality deterioration and, at least in some in the Indian River Lagoon, Florida, USA. They were areas, a decrease in fish species richness (Harrington transported to the laboratory in styrofoam coolers contain and Harrington, 1982; Gilmore et al., 1982). The ing impoundment water where they were held at 25°C species that use these habitats must be able to endure overnight under high aeration or transferred directly into fluctuating and stressful environmental conditions for outdoor concrete vaults (900 I) when environmental temper extended periods of time. For example, sheepshead atures approached experimental temperatures. Experimen minnow and sailfin molly have been reported in tal animals were then transferred to 761 aquaria equipped hypersaline habitats (Gilmore et al., 1982) but are with individual filters, aerators and heaters. They were held good osmoregulators (Gustafson, 1981; Nordlie, in 30 ± 10/00 salinity and 30 ± 1°C under a 12L: 12D photo 1987). These two species and the mosquitofish, Gam period centered at 1230 hr for at least 7 days. Experimental animals were fed Tetramin flake food ad libitum twice daily busia affinis are also able to tolerate low-oxygen but were fasted for 24 hr prior to testing (except the survival tensions (Cech et al., 1985) while mosquitofish, other experiments). In all experiments, sex of the fishes was not mollies (Poulin et al., 1987), and striped mullet, Mugil considered. Experimental salinities were produced using cephalus (Moore, 1976) can behaviorally adjust their filtered (5 /lm) Atlantic Ocean seawater diluted with aged oxygen uptake by aquatic surface respiration (ASR). reverse osmosis water. Salinities were checked daily. The comparative eco-physiology of sheepshead minnow, Cyprinodon variegatus, and sailfin molly, Normoxic lhypoxic blood constituents experimental protocol Poecilia latipinna, from impounded mangrove Fish were netted from their experimental aquaria and swamps is unknown. The objective of this study was immediately measured to the nearest mm standard length to compare and contrast physiological changes be (SL). All blood samples were obtained by first blotting each tween two closely related resident species that differ individual dry and severing its caudal fin. The incision was immediately blotted and blood from the caudal artery was in their use of habitat. To do this, I documented drawn into a heparinized micro-capillary tube and cen hypoxia-induced changes in hematocrit, plasma os- trifuged for 4 min at 13,460g in an International Micro capillary Centrifuge (Model MB) for hematocrit (%) determination. All fish were processed within a 30 min *Present address: Department of Biological Sciences, PO period and individual blood collection was completed within Drawer GY, Mississippi State University, Mississippi I min to reduce handling effects on blood constituents State, MS 39762, USA. (Robertson et al., 1987). All individuals were killed between

17 COP 97A/J-8 18 MARK S. PETERSON

0800 and 0900 hr (Peterson and Gilmore, 1988). Plasma monitored at I, 2, 4, 6, 8, 10, 12 and 24 hr intervals. Death osmolality (rrrOsrn/kgj was determined on a 10 III sample was established when the fish did not move its operculum with a Wescor Vapor Pressure Osmometer (Model 5500). for I min. Throughout this portion of the experiments, Plasma chloride ion concentration (meq/l) was determined water flow rates (121.1 ± 9.0 ml/min) flushed the 0.851 from a 10111 sample on a Buchler Digital Chloridometer tubes, on average, every 7.02 min. Sheepshead minnows (Model 4-2500). Sheepshead minnows (n = 50) were held (n = 5) were held in the experimental conditions for under the above-mentioned conditions for 11.5 ± 0.5 days 19.0 ± 1.0 days and sailfin molIies (n = 5) for 31.0 ± 2.1 and sailfin molIies (n = 30) for 7.0 days prior to experimen days. tation. Hypoxic conditions were produced by bubbling nitrogen gas directly into the aquarium for 3.0 hr. thus Statistical treatments gradualIy reducing the oxygen tension to hypoxic conditions Fish size, osmolality and chloride ion concentration (all (38.5 ± 2.6 mm Hg; about 26% saturation; 1.6 ppm). Fish log 10 transformed) and hematocrits (arcsine transformed) were kept at the new Po, tension for 2.5 hr. Experimental Po, were analysed by Po, treatment by analysis of variance tensions were determined and monitored by injecting a (ANOVA). Oxygen consumption rates were analysed by a single water sample into a calibrated Radiometer PHM paired t-test (alpha = 0.05) whereas oxygen consumption 73/D616/E5046 oxygen analyzer system. The experimental rates vs wet weight were examined by linear regresion. [j is aquaria contained floating styrofoam slabs in order to the mean difference between paired values and only applies reduce surface breathing by sailfin molIies. to the paired t-test. Oxygen consumption rates RESULTS SmalI flow-through respirometers (modified 125 ml Erlen meyer flasks) equipped with two glass tubes, one that Normoxic /hypoxic blood constituents alIowed inflowing water to enter near the bottom of the flask while the other tube alIowed water to pass out of the flask Individual sheepshead minnow sizes ranged from near the bottom of the stopper (top of flask) were used. 24 to 40 and 31 to 45 mm SL for the normoxic and •I Fifteen respirometers were connected by vinyl tubing to a hypoxic experiments, respectively. Sailfin molly PVC manifold that was equipped with nylon valves for ranged from 36 to 54 and 32 to 39 mm SL. There were controlIing water flow rates (26.7 ± 12.4ml/min for min no significant size differences between the normoxic nows; 21.6± 8.7 for molIies). Due to flow rates and and hypoxic individuals (ANOY A; P > 0.05). respirometer size, steady state was achieved rapidly (Propp Significantly (ANOY A; P < 0.05) elevated hem et al., 1982). Water ofthe desired oxygen tension entered the manifold from a 456 I headbox via an acrylic chamber atocrits were documented for both species under (300 m!) which was used to obtain an initial water sample hypoxic conditions (Fig. I). Only sheepshead min with a needle and syringe. Final water samples were taken nows exhibited significantly (ANOYA; P < 0.01) with a needle and syringe from a piece of vinyl tubing elevated plasma osmolality, whereas there were no attached to the glass tube leaving each respirometer. differences in plasma chloride ion concentration for Desired oxygen tensions (mm Hg) were produced by either species (P < 0.05) (Fig. I). passing water from a headbox through an in-line oxygen stripper (Cameron, 1986) made of PVC (152.4 em x 7.94 em Oxygen consumption rates i.d.) and filIed with marbles to increase surface area for nitrogern gas diffusion. Regulation of the counter flows For the size range examined, there was no statisti brought about the desired oxygen levels. cally significant relationship between wet weight and Routine oxygen consumption rates (mg 02/g/hr) were oxygen consumption rates of sheepshead minnow calculated by the equation V02 = (PO,i - Po,,) (a) (1.428) (1.63-3.21 g ww) in either normoxic or hypoxic con V/ww (g) (Lampert, 1984), where (Po,,) = oxygen tension of ditions (ANOY A; P > 0.05). However, sailfin molly inhalent water; (Po,,) = oxygen tension of exhalent water; (0.75-1.84 g ww) exhibited significant (P < 0.05) a = solubility coefficient (from Cameron, 1986); 1.428 con weight-dependent respiration in normoxic but not in verts rnl/l to mg/l oxygen; V = flow rate (ml/hr); and hypoxic conditions (P > 0.05). This normoxic re ww = wet weight (g). Each experiment took a 43.5 hr period. lationship, however, did not explain much of the An individual was placed within each of the respirometers at 1330 hr and held in the chamber for 18.5 hr in normoxic variance (r = 0.41) and thus the data for all sizes were water (minnows = 150.1 mm Hg; molIies = 165.6 mm Hg). pooled and analysed using a paired t-test. Significant Between 0800 and 0900 hr, initial and final Po, readings were reductions in weight-specific oxygen consumption taken as welI as a flow rate for each respirometer. A were documented for sheepshead minnow (paired respirometer without fish was used to adjust for microbial t = 10.70; df = 13; 15= 0.8634; P < 0.001) and sailfin respiration. The fish remained in the chamber for another molly (paired t=6.56; df=13; 15=0.5391; 18.5 hr and then nitrogen was used to gradualIy reduce P < 0.001) under hypoxic conditions (Fig. 2). the partial pressure of oxygen (over the next 3.0 hr) flowing into the respirometers (minnows = 42.2 mm Hg; molIies = Survival experiments 42.8 mm Hg). Once the desired oxygen tension was ob tained, the fish were alIowed 2.5 hr to adjust to the lower For both sailfin molly and sheepshead minnow, oxygen levels. The initial and final hypoxic readings were oxygen tensions of 60 and 40 mm Hg (2.6 and taken between 0800 and 0900 hr. Each sheepshead minnow 1.6 ppm) were not lethal over a 24-hr period (Fig. 3). (n = 14) and sailfin molIy (n = 14) was used only once.

Survival experiments DISCUSSION In order to more adequately address the effects of hypoxia Sheepshead minnow and sailfin molly exhibit stress on these species, survival experiments were set up at 60 and 40 mm Hg. Individual fish were placed in a 0.851 respirom under hypoxic conditions, as indicated by a suite of eter and were held for 18.5 hr under flowing, normoxic secondary stress-response measures. Both species (162.3 ± 13.6) water. Subsequently, between 0730 and showed significant increases in hematocrit under 0800 hr. the oxygen tension was rapidly reduced to either 60 hypoxic conditions. An increase in hematocrit has (59.6 ± 1.2) or 40 (39.6 ± 1.2) mm Hg and death was also been documented in other species in similar Hypoxia-induced physiological changes in two fishes 19

~ 1.2 140 1.0 <:T CIl -S 130 0.8 z 0 0.6 120 • ~ Z I- 0 0.4 z f= W 0- I u 110 ::if s: 0.2 z ::> 0 Vl u z I 0 0' 0.0 1 100 U N 0 U Z 1.2 W 0' C? >- I X S 1.0 lj> 360 0 ~ • • E 0.8 III 0 340 -S 0.6

~ 0.4 :J 320 rr ~ 0 0.2 ::;: en . 0 300 0.0 I 150 40 50 OXYGEN TENSION (mmHg) ~ '--" 40 Fig. 2. Comparison of oxygen consumption rates for ~ sheepshead minnow and sailfin molly in normoxic (ISOmm a::: o 30 • Hg) and hypoxic (40 mm Hg) conditions. Circle = 0 significant difference (P < 0.05). Values are X ± SD. ';;( ::;: 20 W ::I: 10 sheepshead minnows reduced the energy associated with osmoregulation and spent more energy main taining a higher gradient by increasing its ventilation 150 40 150 40 ~ e-w.. lWilIlIaIIlI IoliQIDlIlI Fig. I. Comparison of hematocrit, osmolality and chloride ion concentration in normoxic (150mm Hg) and hypoxic Cyprinodon voriegatus (40 mm Hg) conditions for sheepshead minnow and sailfin 80 molly. Circle = significant difference (P < 0.05) between oxygen tensions. Values are X ± SD. 60

hypoxic conditions and has been indicated as an 40 initial response to hypoxia (Fievet et al., 1987). For example, Swift (1981) documented a significant in 20 crease in hematocrit for rainbow trout, Salmo gaird

neri (= Oncorhyncus mykiss: Smith and Stearley, o+-~...,....,,...... ,....,.-,-...,....,~..,..,~...,....,,...... ,....,.-,-...,....,,.....,--, 1989) exposed to 2.3 mg/l dissolved oxygen (or lower) o 8 12 16 20 24 for periods longer than 3 hr. Swift (1982) also sug gested that increased hematocrit might pre-adapt

fishes to hypoxic conditions, thus allowing them to 80 bind more available oxygen when it is environmen tally low. It is thought that elevated hematocrit is ...i ~ 60 caused by an increased production of erythrocytes, s(l:: fluid loss to the tissues with a subsequent decrease in ::> Vl 40 plasma volume and/or swelling of the erythrocytes ~ (Swift, 1981; Fievet et al., 1987). Although the values obtained in 30%0 salinity and 20

normoxic conditions for both species were similar to G--4 60 mmHg ..... 40 mmH those reported by Gustafson (1981) and Nordlie 0 (1987), there are no osmolality and/or chloride ion 0 4 8 12 16 20 24 data available for sailfin molly and sheepshead minnow in hypoxic conditions. The significant in TIME (hrs) crease in plasma osmolality under hypoxic conditions Fig. 3. Comparison of survival data over a 24-hr period in sheepshead minnow suggests that as the Po, for sheepshead minnow and sailfin molly in two oxygen gradient across the gills decreased under hypoxia, tensions. 20 MARK S. PETERSON rate. Although I was not able to empirically measure manyam (1980) for 1.4-5.6 g ww fish were not ventilation rates in either species, rates were visibly conclusive in terms of weight. Additionally, Barton higher under hypoxic conditions, a phenomena docu and Barton (1987) calculated routine metabolic rates mented in numerous other teleosts under hypoxic using a closed, oxygen depletion technique which conditions (Lomholt and Johansen, 1979; Boese, introduces a series of problems not associated with 1988). In contrast, there were no significant changes flow-through respirometry (Lampert, 1984). These in either plasma osmolality or plasma chloride for problems may have affected large individuals to a sailfin molly, suggesting that this species may have greater extent than small individuals. taken oxygen from the relatively rich surface water The significant reductions in oxygen consumption surrounding the styrofoam slabs, as has been docu rates for sheepshead minnow and sailfin molly are mented in other mollies under hypoxic conditions typical for other fishes held under similar conditions (Poulin et al., 1987) and noticed in this study. (Lomholt and Johansen, 1979; Cech et al., 1985; Since this species is morphologically well adapted to Boese, 1988). The only previous documentation of using the oxygen rich layer of water near the surface the effects of hypoxia on oxygen consumption in (Lewis, 1970), they can survive even low oxygen these two species was a preliminary study by Subrah tensions in nature without significant osmoregulatory many am (1980) in which only three individuals of disfunction. each species were tested. Although both speciesexam Although a significant decrease in metabolic rate ined in this study exhibited reduced oxygen consump with increased weight was seen for sailfin mollies in tion rates in hypoxia, differences in activity between normoxia, Subrahmanyam (1980) and Gustafson the two species were marked. While neither exhibited (1981) documented slight but insignificant reductions mortality in oxygen tensions as low as 40 mm Hg, in weight-specific oxygen consumption with increased sailfin molly activity was markedly increased in weight in the same species. In contrast, there was no hypoxia while sheepshead minnow showed decreased ., significant relationship between metabolic rate and activity. weight in hypoxia. Such variations in oxygen con In summary, hypoxia-induced physiological sumption rates have been documented in a number of changes in the sheepshead minnow and the sailfin fish studies (Eccles, 1985; Boese, 1988). molly were documented. The ability to tolerate Significant weight-related differences in oxygen hypoxic conditions depends upon physiological and consumption rates in the sheepshead minnow as behavioral mechanisms, which differ between these reported by Barton and Barton (1987) were not seen two species. Sailfin molly are morphologically in this study. This discrepancy may have been due to adapted to use ASR whereas sheepshead minnow are differences in the size ranges examined among the not; however, minnows can tolerate significant fluctu studies (Table 1) and/or the techniques used. For ations in their plasma osmolality while mollies can example, Barton and Barton (1987) examined not. Both species are residents of mangrove swamp sheepshead minnows between 0.08 and 0.78 g ww, habitats, where major changes in dissolved oxygen whereas minnows between 1.63 and 3.21 g ww were occur on time scales of hours and thus these species used in this study. This suggests that sheepshead are required to utilize both physiological and behav minnows at sizes above 1.0 g ww may not have ioral mechanisms to deal with hypoxia. Evidence significant size-related oxygen consumption differ from mangrove swamp habitats in east-central ences. The metabolic rates calculated by Subrah- Florida indicates that when environmental conditions

Table 1. Comparison of oxygen consumption rates for sheepshead minnow and sailfin molly Oxygen S T ww Oxygen tension consumption (0/00) eC) N (g) (mm Hg) (mg O,/g/hr) Authority Cyprinodon »ariegatus 35 20 0.08--D.78 Saturation 0.279--D.078 Barton and Barton (1987) 10 20 0.09--D.81 Saturation 0.432--D.155 SW 25 I 0.6 -78 -1.55 Subrahmanyam (1980) -44 -0.23 SW 25 1.3 -85 -0.69 -45 -0.77 SW 25 2.4 -81 -0.39 -43 -0.18 30 30 14 2.14 ± 0.44 150.1 0.88 ± 0.30 Present study 42.2 0.14 ±0.10 Poeci/ia latipinna SW 25 1.4 -85 -0.36 Subrahmanyam (1980) -58 -0.10 3.7 -84 -0.33 -43 -0.08 5.6 -84 -0.27 -41 -0.08

35 25 18 O.75~3.00 90-155 -0.47 Gustafson (1981) 30 30 14 1.24 ± 0.31 165.6 0.55 ± 0.31 Present study 42.8 0.13 ± 0.09 - = Approximate values (from graphs); S = salinity; SW = seawater; T = temperature; ? = temperature not reported; N = sample size; ww = wet weight. Subrahmanyam (1980) used the same individual within a weight for the low and high oxygen tension experiments. Present study values are reported as X ± SD. Hypoxia-induced physiological changes in two fishes 21

deteriorate, C. variegatus undergoes severe mortality salt marsh to prevent breeding by salt marsh mosquitos. while P. latipinna does not (Peterson, personal obser Bull. Mar. Sci. 32, 523-531. vation). Causal factors other than hypoxia that are Lampert W. (1984) The measurement of respiration. In A common in mangrove swamp habitats and affect Manual on Methods for the Assessment of Secondary Productivity in Fresh Waters (Edited by Downing J. A. fishes are high hydrogen sulfide concentrations in and Rigler F. H.), pp. 416-468. Blackwell, Oxford. bottom water and high temperatures. Differential Lewis W. M. Jr (1970) Morphological adaptations of mortality between these two species may be more a cyprinodontoids for inhabiting oxygen deficient waters. function of their typical habitat use pattern (epiben Copeia 1970, 319-326. thic versus surface orientated) than physiological Lomholt J. P. and Johansen K. (1979) Hypoxia acclimation

adaptations to hypoxic stress. Thus, synergistic en in carp-How it affects O2 uptake, ventilation, and O2 vironmental effects come into play in mangrove extraction from water. Physiol. Zool. 52, 38-49. swamps that affect fish survival. Moore R. H. (1976) Seasonal patterns in the respiratory metabolism of the mullets Mugil cephalus and Mugil curema. Contr. Mar. Sci. 20, 133-146. Acknowledgements-v-i wish to thank K. Bird for the use of Nordlie F. G. (1987) Plasma osmotic, Na + and Cl : regu laboratory space and R. Laughlin and G. Gilmore for the lation under euryhaline conditions in Cyprinodon variega use of equipment. Nancy Brown-Peterson and Drs F. G. tus Lacepede. Compo Biochem. Physiol. 86A, 57--ul. Nordlie, T. G. Bailey and R. G. Gilmore reviewed this Odum W. E., Mcivor C. C. and Smith T. J. III. (1982) The manuscript. Doug Scheidt, R. Brockmeyer and J. ecology of the mangroves of south Florida: a community Luczkovich aided with field work. Funding was provided by profile. U.S. Fish and Wildl. Serv., Office of BioI. Services, , a post-doctoral fellowship to MSP by the Harbor Branch Washington, D.C. FWSjOBS-81j24. Institution, Inc. and a grant (CZM-194) to G. Gilmore from Peterson M. S. and Gilmore R. G. Jr (1988) Hematocrit, the Indian River Mosquito Control District. This is contri osmolality and ion concentration in fishes: consideration bution No. 758 of the Harbor Branch Oceanographic of circadian patterns in the experimental design. J. expo Institution, Inc . • Mar. BioI. Ecol. 121, 73-78. Poulin R., WolfN. G. and Kramer D. L. (1987) The effect REFERENCES of hypoxia on the vulnerability of guppies (Poecilia reticulata, Poeciliidae) to an aquatic predator (Astronotus Barton M. and Barton A. C. (1987) Effects of salinity on oce/latus, Cichlidae). Env. BioI. Fishes 20, 285-292. oxygen consumption of Cyprinodon variegatus. Copeia Propp M., Garber M. and Ryabuscko V. (1982) Unstable 1987, 230-232. processes in the metabolic rate measurements in flow Boese B. L. (1988) Hypoxia-induced respiratory changes in through systems. Mar. BioI. 67, 47-49. english sole (Parophrys vetulus Girard). Compo Biochem. Robertson L., Thomas P., Arnold C. R. and Trant J. (1987) Physiol. 89A, 257-260. Plasma cortisol and secondary stress responses of red Cameron J. (1986) Principles ofPhysiological Measurement. drum to handling, transport, rearing density, and a Academic Press, New York. disease outbreak. Prog. Fish-Cult. 49, 1-12. Cech J. J., Massingill M. J., Vondracek B. and Linden A. L. Smith G. R. and Stearley R. F. (1989) The classification and (1985) Respiratory metabolism of mosquitofish, Gambu scientific names of rainbow and cutthroat trouts. Fisheries sia affinis: effects of temperature, dissolved oxygen, and 14,4-10. sex difference. Env. BioI. Fishes 13, 297-307. Subrahmanyam C. B. (1980) Oxygen consumption of Eccles D. H. (1985) The effect of temperature and mass on estuarine fish in relation to external oxygen tension. routine oxygen consumption in the South African Compo Biochem. Physiol. 67A, 129-133. cyprinid fish Barbus aeneus Burchell. J. Fish BioI. 27, Swift D. J. (1981) Changes in selected blood com 155-165. ponent concentrations of rainbow trout, Salmo gairdneri, Fievet B., Motais R. and Thomas S. (1987) Role of adren exposed to hypoxia or sublethal concentrations of phenol ergic-dependent H + release from red cells in acidosis or ammonia. J. Fish BioI. 19, 45--ul. induced by hypoxia in trout. Am. J. Physiol. R269-R275. Swift D. J. (1982) Changes in selected blood component Gilmore R. G., Cooke D. W. and Donohoe C. J. (1982) A concentrations of rainbow trout, Salmo gairdneri, follow comparison of the fish populations and habitat in ing the blocking of the cortisol stress response with open and closed salt marsh impoundments in east-central betamethasone and subsequent exposure to phenol or Florida. Northeast Gulf Sci. 5, 25-37. hypoxia. J. Fish BioI. 21, 269-277. Gustafson D. L. (1981) The influence of salinity on plasma Thayer G. W., Colby D. R. and Hettler W. F. Jr • osmolality and routine oxygen consumption in the sailfin (1987) Utilization of the red mangrove prop root habitat molly, Poecilia latipinna (Lesueur), from a freshwater and by fishes in south Florida. Mar. Ecol. Prog. Ser. 35, an estuarine population. MS Thesis, University of 25-38. Florida, Gainsville, FL. Whitman W. R. and Meredith W. H. (1987) Waterfowl and ,. Harrington R. W. Jr and Harrington E. S. (1982) Effects on Wetlands Symposium. Delaware Coastal Manag. Prog., fishes and their forage organisms of impounding a Florida Delaware Dept. Nat. Res. Env. Control, Dover.