Overlap of mountain clingfish (Gobiesox fluviatilis) and Mexican clingfish (Gobiesox mexicanus) in the Cuitzmala River, Jalisco, Mexico.
Freshwater clingfishes are small benthic fish inhabiting temperate and tropical waters, typically in areas with relatively high water velocity. Perhaps the most distinct characteristic of the group is the presence of joint pelvic fins forming a suctorial disk, used to maintain position under conditions of relatively high flow (Miller et al., 2005). Gobiesox juniperoserrai, described in 1996 (Espinosa-Perez and Castro-Aguirre, 1996), is known from Arroyo las Pocitas (Poza del Vado) in the state of Baja California Sur, Mexico (Ruiz-Campos et al., 2002; Miller et al., 2005), but is now considered extirpated (Ruiz-Campos et al., 2014). Researchers have reported Gobiesox mexicanus from streams in Jalisco, Nayarit, Guerrero, Oaxaca (Miller et al., 2005), and Colima (J. Lyons, pers. obser.). Gobiesox fluviatilis is known from the Cuitzmala, Chapalagana, Grande de santiago, Mezquital, and Fuerte rivers in states of Jalisco, Zacatecas, Nayarit, and Chihuahua (Guzman et al., 2001; Miller et al., 2005; J. Lyons pers. observ.). Presence of G. fluviatilis in the Cuitzmala River was confirmed by Espinosa-Perez et al. (1987) using data from 44 individuals collected in 1985 from freshwater areas 5 km from the mouth of the river to the Pacific Ocean . Morphological evidence had suggested overlap in the distribution of G. mexicanus and G. fluviatilis in the Cuitzmala River (Jalisco) and potentially in Nayarit (Miller et al., 2005), but data were scarce and equivocal. In this note we aim to: a) confirm species overlap in the Cuitzmala River, b) present new morphometric and meristic data for G. fluviatilis and G. mexicanus, c) document a new record size for G. fluviatilis, and d) present physical-chemical and environmental data of sites occupied by the species.
We captured specimens as part of fish community surveys carried out using a DC backpack electrofishing device (ABP-3, ETS Electrofishing Systems LLC, Madison, Wisconsin) at three sites in the mainstem of the Cuitzmala River (Jalisco, Mexico; Fig. 1) during April and May 2013 (dry season). Site 1 (N = 2; coordinates: 19[degrees]49'0"N, 104[degrees]43'4"W) was located at an elevation of ~487 m above sea level, approximately 78 km from the mouth of the Cuitzmala to the Pacific Ocean. This site was located upstream from the town of La Eca, approximately 15 km NW (straight line) from the city of Villa Purificacion, Jalisco. Site 2 (N = 1; 19[degrees]41'45"N, 104[degrees]46'18"W) was located at ~342 m above sea level, approximately 61 km from the Cuitzmala River mouth. The site is located approximately 17 km (straight line) W from Villa Purificacion, Jalisco. Site 3 (N = 1; 19[degrees]34'36"N, 104[degrees]480500W) was located at ~219 m above sea level, approximately 22 km from the Pacific Ocean. The site is approximately 19 km NW from La Huerta, Jalisco.
We fixed Gobiesox specimens from all sites in formalin and later transferred them to 70% ethanol for preservation. We obtained fresh fin tissue from the specimen from site 2 prior to fixation, but not from specimens in sites 1 and 3. We deposited all specimens at the Instituto de Biologia, Coleccion Nacional de Peces of the Universidad Nacional Autonoma de Mexico under catalog numbers CNPE-IBUNAM20405 (site 1); CNPE-IBUNAM20406 (site 2), and CNPE-IBUNAM20407 (site 3). We also deposited preserved tissues at this institution.
[FIGURE 1 OMITTED]
We obtained morphometric and meristic data following Briggs and Miller (1960). We made counts under a stereoscopic microscope (when needed) and used electronic calipers to carry out all measurements. We took X-rays from all specimens to enable vertebrae counts. We compared meristic, diagnostic, and morphometric data obtained from captured specimens with values in original species descriptions (Briggs and Miller, 1960) and documents describing collections of Gobiesox sp. in the Cuitzmala River (Espinosa-Perez et al., 1987).
We collected two specimens of G. mexicanus in site 1, and one specimen of G. fluviatilis in each of sites 2 and 3. Individuals from site 1, specimens 2 (Table 1, column F) and 3 (Table 1, column G), had standard lengths (SL) of 65.2, and 52.7 mm, respectively. These specimens showed dark coloration in the dorsal area and evident lightly colored rings in the anterior portion of the body through the caudal peduncle. On both specimens, the anus was located closer to the edge of the suctorial disk than the origin of the anal fin. However, specimen 2 presented multiple rows of teeth in the lower mandible whereas specimen 3 had a single row of teeth in the lower mandible. We identified these specimens as G. mexicanus.
The specimen that we collected in site 2 had an SL of 137.8 mm (Table 1, column H). The specimen had dark mottled coloration, multiple rows of teeth in the lower mandible, and an anus closer to the edge of the suctorial disk than the origin of the anal fin. We identified the specimen as G. fluviatilis. The specimen collected from site 3 (Table 1, column E) had an SL of 62.8 mm. The specimen had very dark mottled coloration, an anus closer to the edge of the suctorial disk than the origin of the anal fin and a single row of teeth in the lower mandible. We identified the specimen as G. fluviatilis.
Physical-chemical and habitat parameters for each site at the time of sampling were as follows. For site 1: oxygen saturation = 79.3%, dissolved oxygen concentration = 6.33 mg/L, conductivity = 58.9 [micro]S, salinity = 0.0 ppt, temperature = 27.4[degrees]C, maximum water depth recorded at the site = 1.5 m, average depth at a site (taking into consideration all areas sampled at a site) = 0.7 m. For site 2: oxygen saturation = 97.0%, dissolved oxygen concentration = 7.87 mg/L, conductivity = 238 [micro]S, salinity = 0.1 ppt, temperature = 26.6[degrees]C, maximum water depth = 1.0 m, average depth = 0.6m. For site 3: oxygen saturation = 101.0%, dissolved oxygen concentration = 7.86 mg/L, conductivity = 344 [micro]S, salinity = 0.2 ppt, temperature = 28[degrees]C, maximum water depth = 0.6 m, average depth = 0.2 m. All sites were dominated by boulders surrounded by gravel and sand. At the time of sampling, both sites 1 and 2 had stream widths of approximately 10-12 m. They were both located in river areas with relatively high gradient and were surrounded by riparian areas in relatively good condition. Site 3, located lower in the basin, had a wetted width of approximately 20 m and had a relatively perturbed riparian area. In all areas, specimens were captured in rocky habitats with good cover and swift, very low turbidity water. Gobiesox fluviatilis occurred in slightly more saline waters (0.1-0.2 ppt) than G. mexicanus (0.0 ppm).
We collected the clingfishes described here along with multispotted goby (Sicydium multipunctatum) (sites 1-3), leopard splitfin (Xenotaenia resolanae) (sites 1-2), golden livebearer (Poeciliopsis baenschi) (sites 2-3), blackspotted livebearer (Poeciliopsis turneri) (site 2), mountain mullet (Agonostomus monticola) (site 3), and spotted sleeper (Eleotris picta) (site 3). We observed, but did not capture, unidentified cichlids (most likely Oreochromis species) in site 2.
Gobiesocid specimens were first recorded from Mexico by Pellegrin (1901) in the early 1900s from the Chapalagana River, Jalisco, and the Grande de Santiago River and other systems in Nayarit and were originally assigned to panamic clingfish (Gobiesox adustus) (Guzman et al., 2001). Later revisions and descriptive work by Briggs and Miller (1960) gave rise to G. mexicanus and G. fluviatilis. Following these descriptions, several investigations expanded the ranges for these species to include the Mezquital River (Durango), the Fuerte River (Sinaloa), the Cuitzmala River (Burr and Buth, 1977; Espinosa-Perez et al., 1987; Miller et al., 2005), the Chapalagana River in Zacatecas (Guzman et al., 2001), the Mismaloya River (G. mexicanus; Jalisco; J. Lyons, pers. observ.), and the Tamazula River (Culiacan River Basin), Sinaloa (Sanchez-Gonzales et al., 2010). These records, along with our data, suggest an area of overlap for both species between approximately 18[degrees]N and 22[degrees]N in systems draining into the Pacific Ocean. Our data also expands the known longitudinal distribution of Gobiesox along the Cuitzmala River; previous records from this system (Espinosa-Perez et al., 1987) were located 5 km from the mouth of the river while our records locate the genus 17-78 km along the high-gradient river from the Pacific Ocean. This is not, however, the farthest upstream that specimens of G. fluviatilis have been captured; they occur up to ~380 km upstream along the Santiago River at its junction with the Juchipila River (J. Lyons, pers.observ.). This highlights the capacity for this vicariant genus to invade upstream areas.
In addition to potential species overlap, our study indicates there is need for a revision of the Mexican freshwater clingfishes. Our data suggest higher variation in meristic and morphological attributes than formerly known from previously captured specimens. Specifically for G. mexicanus, we found our specimens had a slightly higher (2.8) SL/head length ratio (compared to a maximum of 2.7 in the original description [in italics in the following lines]), a higher bony interorbital space/eye length ratio (1.7-2.0vs. 0.8-1.5), a higher head length/eye length ratio (6.1-6.5 vs. 3.7-6.0); a slightly higher SL/disk length ratio (2.8 vs. 2.7), a lower number of dorsal (8 vs. 9) and pectoral (19-20 vs. 22-24) rays, a slightly higher number of rows of papillae in disk C (6-7 vs. 5-6), and a higher number of vertebrae (28-31 vs. 26-27). Addition ally, specimen 3 had a higher SL/head width ratio (3.1 vs. 2.9). Our G. fluviatilis specimens had lower anal (6 vs. 7) and pectoral (19-20 vs. 21-23) ray counts, and a higher number of papillae on disk C (6 vs. 5). In addition, specimen 4 (137.8 mm SL) had a lower SL/body depth ratio (4.2 vs. 4.4), a lower caudal peduncle length/caudal peduncle depth ratio (0.7 vs. 1.0); a higher bony interorbital space/eye length ratio (3.2 vs. 2.9), and a lower number of vertebrae (27 vs. 29). As suggested by Burr and Buth (1977), some of the variation in specimen 4 could originate from allometric variation.
We report a record size for G. fluviatilis. At 137.8 mm SL, the specimen captured in site 2 is not only the largest ever reported specimen for the species or freshwater Mexican clingfishes, but also one of the largest freshwater gobiesocids reported worldwide. To our knowledge, only clingfish (Arcos nudus) (150 mm SL) and Gobiesox juradoensis (115 mm SL) have been reported to attain similar sizes (Ferraris, 2003).
Both G. mexicanus and G. fluviatilis are listed by NOM059-ECOL-2010 (SEMARNAT, 2010), the Mexican red list for endangered and threatened species. Gobiesox mexicanus is a species subject to special protection. Gobiesox fluviatilis is considered a threatened species. The main considerations for their listing perhaps relate to the relatively small size of known populations, their need for relatively high water quality, and their habitat specificity. The Cuitzmala and other rivers where the genus is present are subject to increasing pressures from water overuse, pollution, and habitat modifications. Efforts to conserve river areas with relatively natural conditions in western Mexico as well as maintenance of natural flow regimes are required to protect their fish communities.
Field work was supported by the World Wildlife Fund and the Centro Universitario Costa Sur, Universidad de Guadalajara via project ON49. L. M. Martinez-Rivera, A. Snyder, W. H. Brandenburg, A. Montes de Oca C., P. Gordon L., L. D. Huerta, and C. Mathuriau assisted at various steps in carrying out this research.
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Submitted 26 August 2015.
Acceptance recommended by Associate Editor, Mark Pyron, 11 January 2016.
Norman Mercado-Silva, * Juan J. Schmitter-Soto, Hector Espinosa-Perez
Centro de Investigation en Biodiversidad y Conservation, Universidad Autonoma del Estado de Morelos; Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos, C.P. 62209, Mexico (NMS)
El Colegio de la Frontera Sur; Av. Centenario km 5.5, Chetumal, Quintana Roo, C.P. 77014, Mexico (JJSS)
Instituto de Biologia, Universidad Nacional Autenoma de Mexico, Circuito Exterior S/N, Ciudad Universitaria, Mexico D.F., C.P. 04510, Mexico (HEP)
* Correspondent: email@example.com
Table 1--Meristic and count data for four specimens of Gobiesox species captured in the Cuitzmala River, Jalisco, Mexico. Data shown follow the uniform plan and sequence by Briggs (1955) and Briggs and Miller (1960). For comparison, meristic data and count intervals for species Gobiesox mexicanus (G.m.) and Gobiesox fluviatilis (G.f.) from literature are included in columns B-D. Data in columns B and C correspond to the original species description in Briggs and Miller (1960) for G. f. and G. m., respectively; data in column D correspond to data in Espinosa-Perez et al. (1987) from the Cuitzmala River for G. f. Data in columns E-H are for individuals captured in sites visited in 2013. Abbreviations: SL = standard length, BD = body depth, CPL = caudal peduncle length, CPD = caudal peduncle depth, NA = not applicable, HL = head length, HW = head width, BIS = bony interorbital space, EL = eye length, SnL = snout length, DL = dorsal fin length, PDCD = postdorsal caudal distance, LDisk = disk length, RowC = Rows of papillae on disk C, RowA = Rows of papillae on disk A. Variables B C D Specimen/species G.f. G. m. G.f. No. of individuals 20 11 44 Site Various Various Cuitzmala SL (mm) 24.2-58.8 17.5-68.8 19.6-106.2 SL/BD 5.7 (5.4-6.4) 5.1 (4.7-5.6) 5.2 (4.4-5.5) CPL/CPD 1.1 (1.0-1.2) 1.1 (1.0-1.2) NA SL/HL 2.7 (2.6-2.8) 2.5 (2.4-2.7) 2.5 (2.2-2.5) SL/HW 3.1 (2.9-3.3) 2.8 (2.6-2.9) 2.3 (2.2-2.4) BIS/EL 1.1 (0.9-1.3) 1.2 (0.8-1.5) 2.7 (2.0-2.9) HL/EL 5.4 (5.1-6.0) 5.0 (3.7-6.0) 7.1 (6.5-7.9) HL/SnL 3.1 (2.9-3.3) 3.1 (3.0-3.2) 2.8 (2.8-2.9) DL/PDCD 1.2 (1.1-1.3) 1.3 (1.0-1.5) NA SL/LDisk 2.8 (2.7-3.1) 2.7 (2.6-2.7) NA Dorsal rays (no.) 10 (9-10) 9 (9-10) 9 (9-10) Anal rays (no.) 8 (7-9) 7 (6-8) 8 (7-8) Pectoral rays (no.) 22 (21-23) 23 (22-24) 22 (22-23) Caudal rays (no.) 10 (9-10) 11 (10-12) 12 (12-13) RowC 4 (3-5) 5 (5-6) NA RowA 5 (5-6) 7 (6-8) NA Vertebrae (no.) 30 (29-31) 26 -27 NA Variables E F G H Specimen/species 1 (G.f) 2 (G. m.) 3 (G. m.) 4 (G.f) No. of individuals 1 1 1 1 Site Cuitzmala Cuitzmala Cuitzmala Cuitzmala 3 1 1 2 SL (mm) 62.8 65.2 52.7 137.8 SL/BD 5.2 5.3 5.5 4.2 CPL/CPD 1.0 1.1 1.1 0.7 SL/HL 2.7 2.8 2.8 2.3 SL/HW 2.9 3.1 2.8 2.4 BIS/EL 1.9 2.0 1.7 3.2 HL/EL 5.9 6.1 6.5 8.5 HL/SnL 3.4 2.9 3.0 2.9 DL/PDCD 1.2 1.3 1.1 1.2 SL/LDisk 2.9 2.8 2.8 3.0 Dorsal rays (no.) 9 8 8 9 Anal rays (no.) 6 6 6 6 Pectoral rays (no.) 19 20 19 20 Caudal rays (no.) 13 12 11 11 RowC 6 6 7 6 RowA 5 7 6 6 Vertebrae (no.) 29 (a) 28 (a) 31 (a) 27 (a) Small specimen size made these counts difficult.
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|Author:||Mercado-Silva, Norman; Schmitter-Soto, Juan J.; Espinosa-Perez, Hector|
|Date:||Mar 1, 2016|
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