Introduction

In recent decades, conservation biologists have turned to datasets and expertise from paleontology and archaeology to provide baselines for environmental management (Frazier, 2007; Humphries & Winemiller, 2009). Often, such research focuses on skeletal or exoskeletal remains recovered from paleontological or archaeological contexts of known age that date prior to contemporary human impacts, such as urbanism, industrial agriculture, and modification of rivers. Such research has been termed “applied zooarchaeology” (Lyman, 1996) or “applied paleozoology” (Wolverton & Lyman, 2012; see also Dietl et al., 2015); we use the term applied zooarchaeology in this paper. Applied zooarchaeological data are particularly valuable for understanding biogeographic shifts in species’ ranges over time (Peacock et al., 2012). Like many rivers in the US, the ecosystems associated with waterways in New Mexico have been highly modified over the last century due to impoundment for power, irrigation for agriculture, and provisioning of water for municipalities. As a result, the distribution of aquatic species is likely to have been altered as connectivity along rivers has been interrupted. If modern human impacts on the rivers of New Mexico have caused range constrictions for native fish species, the extent of such changes is unclear. One such species that exhibits ambiguous range constriction is the blue sucker (Cycleptus elongatus Lesueur, 1817 Catostomidae).

The blue sucker was listed as endangered in the state of New Mexico in 1976. Not much is known about the historic range of this species because of how difficult it is to find during surveys. Its current distribution in the state is in the Pecos River drainage basin, and the most stable populations are found in the Lower Pecos between the Brantley and Avalon dams (Propst, 1999). However, in 1961, Gehlbach & Miller reported the presence of two archaeological blue sucker skeletal specimens from Rainbow House (site number: LA 217), which is located in Bandelier National Monument and was occupied from approximately A.D. 1400 to 1600. The authors suggested that in the past the blue sucker occurred farther north than was previously thought when temperature and flow in the Rio Grande were more stable. At best, the zooarchaeological data reported by Gehlbach & Miller (1961) are treated as an ancillary piece of conservation evidence concerning the past distribution of blue sucker, and at worst they are rejected in terms of their meaning for biogeography and conservation. For instance, (Propst, 1999, p. 52) states that “[a]lthough archaeological evidence from Native American ruins indicates the blue sucker inhabited the Rio Grande in New Mexico… no specimens exist to confirm its historic occurrence there.”

In this paper, we report new data on blue sucker remains from the archaeological site of Ponsipa’akeri (LA 297; hereafter Ponsipa). Further, we provide evidence from additional archaeological sites that indicate the historic range of blue sucker included the Upper Rio Grande. If the blue sucker occurred farther north than previously recognized, then the extent of habitat loss for this species is dramatically larger than currently accepted. If so, the identification of relict populations in the Rio Grande may be worthwhile and restoration of this species might be defensible.

Systematics, distribution, and life-history

Until recently, it was believed that the blue sucker was monotypic at the genus level within the family Catostomidae (subfamily Cycleptinae). Burr & Mayden (1999), however, formally described the southeastern blue sucker (Cycleptus meridionalis Burr & Mayden, 1999 Catostomidae) based on scale counts, lip morphology, body measurements, and head morphology. C. meridionalis is only found in the gulf slope drainages of the Mississippi River Basin, and C. elongatus is distributed throughout the interior of North America (Fig. 1). It occurs in the Mississippi River Basin with smaller populations in the Rio Grande Basin, mainly around Big Bend National Park. Even more recently, Bessert (2006) provided phylogenetic information that suggests the blue suckers present in the Rio Grande Basin are a distinct species. It is unclear how past populations entered into the Rio Grande, but researchers posit that either lateral or coastal migration occurred during the Miocene (Bessert, 2006). Within the Rio Grande Basin, during the historic period, blue suckers were recorded in the Pecos River from the Carlsbad area to the Texas/New Mexico border (Propst, 1999). Blue suckers also inhabit lower portions of the Black River (Cowley & Sublette, 1987; Zymonas & Propst, 2007). Zymonas & Propst (2007) found that the range of blue sucker decreased dramatically in the Pecos from 2001 to 2006 due to massive fish kills caused by golden algae blooms. Although some biologists argue that range-wide declines, especially in the Rio Grande, are an artifact of sampling effort (Burr & Mayden, 1999), the consensus is that the blue sucker is experiencing significant range reduction (see Williams et al., 1989; Bessert & Ortí, 2008). This seems to relate to two factors: first, the presence of dams that inhibit spawning migration and gene flow, and second, an increase in stream contaminants related to runoff.

Fig. 1
figure 1

North American distribution of blue sucker (Cycleptus elongatus) and southeastern blue sucker (Cycleptus meridionalis) based on its presence in watershed. Areas of likely extirpation for C. elongatus are also mapped. Distribution data provided by NatureServe

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The blue sucker has a periodic life-history strategy, which is characterized by long generation times, older ages at sexual maturity, large body size, high fecundity, and low juvenile survivorship (Winemiller & Rose, 1992). It is a large-bodied benthopelagic fish with a total length of approximately 66 cm, and it is a relatively long-lived fish with a maximum age around 22–37 years (Bednarski & Scarnecchia, 2006; Labay et al., 2011). Common foods of blue sucker include midge and caddisfly larvae as well as algae (Sublette et al., 1990; Walburg et al., 1971). The age at sexual maturity for blue suckers is approximately 3-years old; females mature faster than males and exhibit larger sizes (Moss et al., 1983). Generation times are roughly 10 years (Bessert & Ortí, 2008). C. elongatus is a non-guarding annual spring spawner (April–June) that can migrate hundreds of kilometers upstream to deposit young in deep riffles that have coarse substrate (Moss et al., 1983; Mettee & Shepard, 1997). In the middle Missouri River, blue suckers rely heavily on different habitat types between spring and summer (Neely et al., 2010). Particularly preceding spawning, blue suckers choose to occupy habitats with reduced water velocity as a way to reduce the energetic costs of reproduction. Post spawning, blue sucker prefer habitats with an increased amount of food sources. Juvenile blue suckers are more commonly affiliated with off-channel habitats than with main channel habitats in the Mississippi River, and they frequently feed on invertebrates associated with vegetated islands (Adams et al., 2006).

The biogeography and life-history ecology of blues suckers indicate that river connectivity, flow rate, and primary and secondary production are crucial for their reproduction and for the survival of juveniles. Further, as a large-bodied fish with a long reproductive cycle that travels long distances to spawn, the blue sucker is vulnerable to population reduction in the face of declining habitat availability and connectivity.

Materials and methods

Study site

Ponsipa is located about 53 km northeast of Rainbow House on the east bank of the Rio Ojo Caliente—nearly 435 km away from where blue suckers are currently found on the Pecos River (Zymonas & Propst, 2007). The site is approximately 15 km upstream from the confluence of the Rio Ojo Caliente and Rio Chama, and from there the Rio Chama joins with the Rio Grande about 9 km downstream. Ponsipa included three cultural occupations, and the peak population at the site was around 1350 people (Duwe, 2011). The site was excavated in 1910 by Sylvanus Morley and from 1979 to 1981 by David Bugé. Blue sucker remains were recovered during Bugé’s excavation, most of which derive from sedimentary deposits late in the site’s occupational sequence.

Blue sucker identification at Ponsipa

Comparative collections, which are libraries of skeletal specimens of known taxonomy, are imperative for precise zooarchaeological identifications (Lyman, 2010). The Ponsipa ichthyofauna was identified using three comparative collections—at the University of North Texas, Laboratory of Zooarchaeology; the Vertebrate Paleontology Laboratory located at the University of Texas; and at the Museum of Southwestern Biology housed at the University of New Mexico. Each bone and bone fragment from Ponsipa received individual attention to avoid taxonomic designation based on what had previously been identified in the assemblage, which is a problem known as identification by association (see Driver, 1992; Wolverton, 2013). Positive identifications to blue sucker were made through morphological comparison to multiple sucker skeletal specimens. In addition to comparative specimens, guides and keys can also be useful in aiding faunal identification. The main key used for identification of skeletal elements in this study comes from Branson (1962), though other sources were used (Nelson 1948, 1949; Gehlbach & Miller, 1966; Eastman, 1977, 1980; Olsen, 1968).

When identifying faunal remains from archaeological sites, it is important to recognize taxa that potentially overlap in skeletal morphology, and thus their remains can be difficult to distinguish (Wolverton, 2013). There are four sucker species that are anticipated to occur in the Upper Rio Grande: the blue sucker, the Rio Grande sucker (Catostomus plebeius Baird & Girard, 1854 Catostomidae), the white sucker (Catostomus commersonii Lacepède, 1803 Catostomidae), and the river carpsucker (Carpiodes carpio Rafinesque, 1820 Catostomidae) (Sublette et al., 1990). Unlike the blue sucker, which is in the subfamily Cycleptinae, the Rio Grande sucker is in the subfamily Catostominae and is a small-bodied fish with a maximum total length at 20 cm. The common total length of blue sucker is approximately three times as great as the maximum total length of Rio Grande sucker. Therefore, we assume that blue sucker skeletal remains can be distinguished from Rio Grande sucker based on this difference in body size. The white sucker, also in the subfamily Catostominae, is a large-bodied sucker and might be difficult to separate from the blue sucker, but this species was introduced to the Rio Grande in the mid to late nineteenth century and was not present in the Upper Rio Grande during the late prehistoric/early historic periods. The river carpsucker is, however, a relatively large-bodied catostomid belonging to the subfamily Ictiobinae that is native to the Upper Rio Grande and might be difficult to separate from the blue sucker. Therefore, it is important to describe osteological criteria for distinguishing blue sucker skeletal remains from those of river carpsucker.

Results

Blue sucker remains from Ponsipa

Blue sucker remains from Ponsipa provide an additional point of reference, along with those reported by Gehlbach & Miller (1961) who document the extent of this fishes’ distribution in the Rio Grande basin. Fish specimens are common at Ponsipa, and 10 blue sucker specimens were identified. The blue sucker specimens are represented by eight skeletal elements: the urohyal, pharyngeal, opercle, maxilla, cleithrum, parasphenoid, hyomandibular, and basipterygium. Only one of each skeletal element is represented at the site except for the cleithrum and basipterygium, each of which are represented by two elements. General osteological characteristics and terminology utilized below derive from Rojo (1991).

Smith (1992) utilized the urohyal to construct phylogenies of members of the family Catostomidae, and from his analysis it is clear that the cycleptine urohyal is morphologically distinct at the subfamily level. As Gehlbach & Miller (1961) noted, the backward oriented wings of the urohyal are diagnostic in C. elongatus. The process on the urohyal of the carpsucker is split (Fig. 2a). The pharyngeal arch and teeth of C. elongatus are robust, and compared to the river carpsucker the pharyngeal arch is slender and the teeth are fine (Fig. 2b). The opercle of the blue sucker has a rounded posterior angle and dorsal edge, while the carpsucker has a sharp posterior angle and a flat to concave dorsal edge (Fig. 2c). The caudal process of the maxilla is dorsoventrally oriented in C. elongatus, while it is twisted in the C. carpio (Fig. 2d). The cleithra of blue sucker have a pinched dorsal narrow strut and a more robust body, the cleithra of the carpsucker is narrow and has a dorsal narrow strut that gradually tapers to a point (Fig. 2e). The alar process of the parasphenoid in the blue sucker is oriented downwards and the midpart of the parasphenoid body has prongs, while these features are absent in the river carpsucker (Fig. 2f). The hyomandibular exhibits an accentuated S-shape in C. elongatus with a projected pterotic facet, and is straighter in shape with a less pronounced pterotic facet in the river carpsucker (Fig. 2g). Finally, the posterior process of the basipterygium in C. elongatus, as evidenced by Branson (1962), is less pointed with a more laterally oriented external process, and the posterior process is more pointed in the river carpsucker with an external process that points directly forward (Fig. 2h). Based on these characteristics, the remains from Ponsipa can be identified to blue sucker.

Fig. 2
figure 2

Archaeological blue sucker (Cycleptus elongatus) specimens from Ponsipa compared to modern blue sucker comparative specimens and modern river carpsucker specimens (Carpiodes carpio). A urohyal, B left pharyngeal arch, C right opercle with arrow pointing to posterior angle and the dotted line showing the shape of the dorsal edge, D right maxilla with arrow pointing to caudal process, E cleithra with arrow pointing to dorsal narrow strut, F parasphenoids with arrow pointing to alar process, G left hyomandibular with arrow pointing to the pterotic facet, and H left basipterygium with arrow pointing to posterior process

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The early historic distribution of blue sucker in northern New Mexico

In addition to the remains from Ponsipa, Gehlbach & Miller (1961) reported the presence of a blue sucker urohyal bone and an incomplete Weberian apparatus from Rainbow House, which was occupied ca. A.D. 1400 to 1600 (Kohler, 2004). In regards to the identifiability of the urohyal bone, Gehlbach & Miller (1961, p. 5) state that “[w]ith its broad, strongly developed wings directed obliquely backward and originating at the anteroventral end of the bone, the urohyal is unlike that of any other genus of North American sucker and this establishes without question its pertinence to the monotypic genus Cycleptus.” Concerning the date blue sucker remains were deposited at the site, Gehlbach & Miller (1961) specify that the “bones were associated with Kidder’s Glaze IV pottery, which dates them between approximately 1550 and 1600 A.D.” The historic period in the northern Rio Grande region is generally regarded as starting at A.D. 1540 with Francisco Vázquez de Coronado’s entrada (Barrett, 2009), suggesting that blue suckers were in the northern Rio Grande during the historic period.

Sixteen years after excavations ceased at Rainbow House, Caywood (1966) compiled a site report in which he mentioned the blue sucker remains identified by Gehlbach & Miller. Caywood described five additional blue sucker specimens from Rainbow House that were identified by Miller as four basipterygia and one lateral ethmoid. These specimens suggest that people were exploiting blue sucker from either the Rito de los Frijoles, the tributary that runs through Bandelier National Monument, or the Rio Grande less than 3 km away.

Blue suckers appear to have been more ubiquitous in the archaeological record of the Upper Rio Grande than once thought (Fig. 3). In addition to the specimens from Rainbow House and Ponsipa, blue sucker remains have been reported from three other archaeological sites. In addition, Sublette et al. (1990) noted the possibility that blue sucker remains were recovered farther downstream. Particularly, the authors mention sites related to the Cochiti Dam Archaeological Salvage Project. This assertion was corroborated by Snow (2002). In one of the few publications detailing how fishes may have been utilized in the region during the late prehistoric and early historic periods, Snow (2002) reports three sites, two of which are from the Cochiti Dam project, from the Northern Rio Grande from which C. elongatus specimens were identified in 1983 by W. J. Koster, the former Curator of Fishes at the University of New Mexico. While the current study has gone to great lengths to ensure that specimens from Ponsipa represent blue sucker, the identifications given by Koster are assumed to be accurate because of his extensive experience in handling fish specimens from New Mexico. The three archaeological sites that have gone unmentioned in the conservation literature are Palace of the Governors (LA 4451) that was occupied from A.D. 1605 to 1692, Alfred Herrera (LA 6455) occupied around A.D. 600 to 1600, and Pueblo del Encierro (LA 70), which was occupied from A.D. 1300 to 1600. Both Alfred Herrera and Pueblo del Encierro were excavated as part of the Cochiti Dam project.

Fig. 3
figure 3

Distribution of blue sucker (Cycleptus elongatus) in the Rio Grande Basin based on its presence in watershed. Five archaeological sites where blue sucker (Cycleptus elongatus) has been identified in the Northern Rio Grande (NRG) region are highlighted. Areas of likely extirpation for C. elongatus are also mapped. Distribution data provided by NatureServe

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Discussion

It is clear that the pre-impoundment distribution of the blue sucker was more extensive in the state of New Mexico at the start of the historic period than it is today, which may relate to installation of impoundments on the Rio Grande. The extent of spawning migration is a key attribute of the blue sucker’s periodic life-history strategy. Although this species is adapted to periods of discontinuity from intermittent flow that sometimes characterizes the Rio Grande, it is also adapted to rapidly take advantage of the re-establishment of continuity and increased flow in river systems. For the blue sucker, the fragmentation of its habitat caused by impoundments creates permanent discontinuity and severely disrupts migration and spawning. One way to promote increased habitat connectivity for this species, and potential re-establishment of past range is through the construction of fishways. Cooke et al. (2005) note that relatively little work has been done understanding how suckers utilize fishways. The construction and monitoring of fishways in the lower Pecos might be a good way to assess the feasibility of reconnecting past habitat and thus, possibly, restoring blue sucker in the Rio Grande.

In addition, it is possible that relict populations exist in the Rio Grande that have not been found during contemporary fish surveys. If relict populations are encountered, it is clear that they should be targeted for conservation based on applied zooarchaeological data indicating range curtailment during the historic period. The Comprehensive Wildlife Conservation Strategy for the state of New Mexico (New Mexico Department of Game and Fish, 2006) has no clear management plan for this species, and labels its monitoring as “periodic.” For any new sampling and more effective management to be done, a clear conservation strategy is required.

Finally, the taxonomic status of the blue sucker in the Rio Grande is in question. Bessert (2006) found that Rio Grande blue suckers form a unique clade among other populations of C. elongatus and C. meridionalis. This clade seems to have diverged almost ten million years ago. Such data may lead to the formal taxonomic description of a new species of cycleptine in the Rio Grande. If this does occur, Rio Grande blue sucker would be a prime candidate for federal listing as an endangered species, and its conservation in the state of New Mexico is warranted.

Conclusion

It has been 55 years, since Gehlbach & Miller published their novel paper on archaeological blue sucker remains at Rainbow House in the American Southwest, and, since then, little research has been reported on the pre-impoundment distribution of blue sucker in the state of New Mexico. With increased sample size from Rainbow House, reporting of remains from three additional archaeological sites, and new data from Ponsipa, it is clear that the extent of the blue sucker’s pre-impoundment distribution included the Upper Rio Grande. This zooarchaeological evidence indicates that range decline in this species has been dramatic, and should the Rio Grande blue sucker be formally described as a species, it may meet criteria to be considered federally endangered. The Northern Rio Grande region has recently received renewed archaeological attention (see Ortman, 2012; Vierra, 2013 and references therein), and it is possible that with new zooarchaeological data, a clearer early historic distribution of the blue sucker will continue to be revealed.