Status ofthe pearl darter (Percidae: Percina aurora) in the Pascagoula River, Mississippi William T. Slack*, Ryan J.Heise^, Mark A. Dugo^ and John A. Ewing, itf ^Mississippi Department of Wildlife, Fisheries andParks Museum ofNatural Science Conservation Biology Section Research and Collections Program ^The University of Southern Mississippi Department ofBiological Sciences Funded by U.S. Fish and Wildlife Service Jackson Field Office Jackson, Mississippi Contract Number: 1448-40181-OO-G-097 2002 STATE: Mississippi PROJECT TITLE: Conservation ofthe pearl darter, Percina aurora Suttkus and Thompson STUDY TITLE: Survey ofthe lower Pascagoula drainage CONTRACT NUMBER: 1448-4018l-OO-G-097 PROBLEM AND NEED The pearl darter, Percina aurora, originally occurred in the Chickasawhay, Leafand Pascagoula River systems ofthe Pascagoula drainage, and in the Pearl and Strong River systems ofthe Pearl drainage (Suttkus et al. 1994) (Fig. 1). The pearl darter was last taken from the Pearl drainage during the early 1970's, and it is now assumed that both Mississippi and Louisiana populations in the Pearl drainage are now extirpated (Bart and Suttkus 1995). Recent and current survey efforts have been conducted in the upper Pascagoula drainage (i.e.. Leafand Chickasawhay rivers) by research groups at Tulane University (Bart et al. 2001) and The University ofSouthern Mississippi (Ross et al. 2000). Although limited in number, historic records exist for the lower Pascagoula drainage (Suttkus et al. 1994) and sampling efforts in the lower Pascagoula drainage during 1999 confirm that populations ofPercina aurora continue to exist within this portion ofthe drainage (MMNS 23466, n = 4; 23>196, n = 1). Additional survey efforts are needed to update the distributional status ofthe pearl darter, Percina aurora, in the lower Pascagoula drainage. This information will be beneficial for addressing the potential decline ofthe pearl darter in the Pascagoula drainage, and in providing critical insight for making decisions concerning the recovery ofthis species. 90- 89 MISSISSIPPI 33 33 32' 32 31 31"* LOUISIANA Figure 1. Historic distribution ofPercinaaurora inLouisiana and Mississippi based on Suttkus et ai. (1994). The star represents the typelocality on the Strong River (Simpson Co., MS). The primary objective ofthis study was to survey the main stem ofthe lower Pascagoula River from Merrill (George Co.) south to divergence ofthe east and west channels ofthe Pascagoula River (Jackson Co.) for the presence ofPercina aurora. The majority ofsampling efforts were confined to the river proper with major tributaries sampled at their confluence with the Pascagoula River. MATERIAL AND METHODS The project area (Merrill to E-W channel divergence) consists ofapproximately 110 river kilometers (RKM). Based on our success in collecting Percina aurora during 1999, sampling efforts focused primarily on deep water habitats (e.g., scour holes) adjacent to sandbars, although additional macrohabitats were sampled (e.g., shallow sand flats, secondary channels). All sites were sampled with a 1.8 x 3.1 m (6 x 10') or 1.8 x 6.1 m (6 x 20') straight seine with 3.2 mm (1/8") Delta mesh. Numerous sites were also sampled with a 45.7 x 2.4 m (150 x 8') bag seine (2.4 X2.4 X2.4 m bag) comprised of6.35 mm (1/4") Delta mesh on the wings and 3.2 mm (1/8") Delta mesh for the bag. One end ofthe bag seine was tethered on the shore, and the bag seine was deployed from the bow ofa boat while the boat was maneuvered in a semi-circular path toward the shoreline in a downstream direction. Once deployed, the net was slowly pulled toward the shore with captured fishes fimneled into bag portion ofthe net. In addition, baited miimow traps (45.7 cm L x 20.3 cm W x 20.3 cm, 0.64 cm galvanized steel mesh, 2.54 cm diameter opening) were placed near cut banks and snags in main channel areas, and allowed to fish for at least 24 hours. Large fishes were generally identified and enumerated in the field and released. Smaller fishes were preserved in 10% formalin in the field, returned to MMNS for processing and curated 4 into the Mississippi Museum ofNatural Science (MMNS) Ichthyology Collection. Captxired pearl darters were anesthetized with MS222 (tricaine methanesulfonate), measured to the nearest 0.5 mm standard length (SL) using a plastic rule, and weighed to 0.01 g using a portable electronic field balance. After processing, pearl darters were transferred to a container offresh stream water containing anti-stress medication (Stress Coat ®) and observed until they had resumed normal activity. After recovery, darters were released at point oforiginal collection. Voucher specimens ofpearl darters were retained when (1) specimens represented a new unique locality or (2) field identification ofpearl darter specimens was uncertain (e.g., YOY). No more than two individuals were vouchered per unique locality; however, a representative series was generally preserved for YOY specimens. Sampled habitats were characterized in terms ofdepth (m), surface water temperature (C), bottom water temperature (C), dissolved oxygen (mg/1) and substrata. All sites were georeferenced (without differential) with a Garmin GPS 12XL (NAD1927). RESULTS Sampling occurred in two phases with the primary phase occurring 4 October - 8 November 2000 (FALL) and the secondary phase occurring 30 May -1 June 2001 (SPRING). Total sampling efforts yielded 81 samples (FALL = 71; SPRING = 10). Pearl darters were present at 28 sites yielding 145 specimens; however, the majority ofthe sites had relatively low abundances ofpearl darters (1-4 individuals) (Fig. 2 and 3). During FALL sampling, 59 total pearl darters were documented at 20 ofthe 71 sites with a mean of2.95 individuals per site • Absent Leaf River Chickasawhay River • 1 -4 • 5-10 O 11 + George B ack Creek Red Creek Pascagoula River Jackson 14 Kilometers Figure 2. Sampling localities and abundance of pearl darters inthe Pascagoula River during 2000 (seines and minnowtraps) and 2001 (seines). O YOY 2001 Leaf River Chickasawhay River • Adult 2000 George B ack Creek Red Creek Pascagoula River Jackson 14 Kilometers Figures. Distribution of sampling effort forpearl darters during 2000 and 2001, (range: 1-12 individuals). All gear types were fished during FALL samples, however the baited minnow traps failed to produce pearl darters. SPRING sampling yielded 86 total individuals from 9 ofthe 10 sites with a mean of 8.6 individuals per site (range: 2-22 individuals). Only the 1.8 X6.1 m (6 X20') straight seine was utilized during SPRING sampling. Two ofthe SPRING sites were also FALL sampling sites, and pearl darters were documented during both periods. Length frequency histograms for all data combined (2000-2001) indicate two age classes (Fig. 4). The abundance ofYOY during SPRING samples (n = 86) from among several localities YOY 2001 Adu t 2000 11=86 10 sites (present at 9) 2-22 individuals (8,6/site) o <0 15 3 O" 0) ^ 10 0 5 10 15 20 25 30 35 40 45 50 55 60 65 Standard length (nim) Figure 4. Length frequency histogram for pearl darters sampled during 2000 and 2001 from the Pascagoula River. provides evidence ofrecruitment ofpearl darters in the Pascagoula River. A linear regression of size (standard length) versus RKM where the sample was conducted (FALL data only) indicates no significant longitudinal pattern of fish sizealong thesection of riversampled (r^ = 0.0031, F(i 57) = 0.180, P = 0.6720) (Fig. 5). Similarly, there wasno significant correlation between pearl darter abundance and RKM (r^ =0.0865, F^, ,9) = 1.800, P = 0.1956). 50 48 46 H •• 44 —r •• 42 - •• H-i 00 40 - •• 38 - 36 RKM vs SL (mm) linear regression ofRKM vs SL 34 140 120 100 80 60 40 20 (upper Pascagoula River) (lower Pascagoula River) River kilometer Figure 5. Plot ofadult pearl darter length (2000 data only) versus river kilometer (RKM) at point ofcapture along the Pascagoula River. Point ofzero kilometer is the L & R Railroad crossing S ofHwy 90 at Gautier, MS. Bottom water temperature (C) for all FALL samples ranged 18.4 to 28.0 (X = 22.7) and dissolved oxygen (mg/1) ranged 2.7 to 8.8 (X = 7.6). Lower stations (RKM 26-37) experienced elevated salinity levels (ca. 5.0 ppt) accentuated by the drought conditions during 2000 and low monthly discharge typical during October and November. Stations where pearl darters were present did not differ appreciably as bottom water temperature (C) ranged 21.2 to 26.5 (X = 22.8) and dissolved oxygen (mg/1) ranged 6.6 to 8.5 (X = 7.7). Bottom water temperature (C) for all SPRING samples ranged 26.6 to 28.9 (X = 27.8) and dissolved oxygen (mg/1) ranged 4.9 to 6.25 (X = 5.4). I Within the Pascagoula, we found pearl darters typically associated with the following riverine features: scour holes on the inside bend ofthe river downstream from a point bar; banks with good slope with water depth reaching 1.5 m at a distance of4-7 m from shore; and substrata primarily ofcoarse sand with an accumulation ofdetritus in troughs perpendicular to the shoreline (Fig. 6). DeMtus typically consisted ofleaflitter, especially cypress needles, and small woody debris. In many ofthese areas hydrogen sulfide gas was readily displaced from the substrata while conducting sampling. Water flow in the adjacent main channel was generally appreciable. These scour hole habitats were in close proximity to the main channel, and as such, experienced good lateral exchange with the main channel. Jin contrast, pearl darters were generally not present at sites with shallow, homogenous sand flats, free ofdetritus, where compact sand was the dominant substratum. Site specific data are listed in Appendix I along with information on pearl darter abundance and size. Based on all sampling gears and both SPRING and FALL samples, 56 total taxa were documented (Table 1).