How American eels Anguilla rostrata construct and respire in burrows

Abstract

We investigated the burrowing behaviour of growth-phase (yellow) American eel Anguilla rostrata, a nocturnal fish that occupies the substrate during daylight hours and during winter. Eels formed burrows by forcing the head, then the body, into the substrate with rapid body undulations. Eels excavated from mud showed highly variable postures. In 10 of 15 experiments, the eel's mouth was at or slightly above the surface. In the remaining experiments, the eel's mouth was a mean of 3.5 cm below the surface, and an inhalation shaft ran from the surface to the mouth. Eels probably advance through mud by alternately pushing and anchoring the anterior and posterior parts of the body. Eel burrows observed in the lab and the field had up to 5 openings. Craters or mounds formed around some winter burrow openings due to head or tail movements or sediment erosion. Flat openings and openings in which the eel plugged the burrow entrance were found in both summer and winter. Dye trace experiments indicated that eels in mud and pebble burrows draw water from the water column into the mouth and exhale it through the gill openings. Because eels in burrows use water from the water column for respiration, the spread of anthropogenically induced anoxia and hypoxia in coastal waters poses an increasing conservation threat. KEY WORDS: Burrowing behaviour · Burrow morphology · Branchial respirationResale or republication not permitted without written consent of the publisher Aquat Biol 19: 287-296, 2013 but no clear link has been established between any threat and the total size of the panmictic population (Casselman 2003, COSEWIC 2012.Some fish species spend much or most of their time in the substrate, either in self-dug burrows (Atkinson & Taylor 1991) or in natural cavities (Ménard et al. 2008). Substrate occupancy may reduce the risk of predation, protect against strong currents, or serve as a base for feeding (Bozzano 2003, Ménard et al. 2008. Yellow-stage anguillid eels generally forage nocturnally, but spend the day in the substrate, either in burrows excavated in soft sediments, or in spaces among rocks or bottom debris (Glova 2002, Tesch 2003. In temperate regions, anguillid eels occupy the substrate throughout winter (Smith & Saunders 1955, Thomas 1968. Aoyama et al. (2005) made resin casts of burrows excavated by Japanese eels Anguilla japonica (Temminck & Schlegel 1846) in a tidal channel, and found that burrows had up to 3 openings and ranged in depth from 18 to 30 cm. Wintering burrows of American eels may show a visible depression (pock mark) at the surface (Smith & Saunders 1955), but visible marks have not been reported for summer burrows. In eastern Canada, Vladykov (1955) reported that several eels may share the same wintering hole in fresh water.Seafloors of many bays, estuaries, and inland waters of eastern North America have been profoundly altered by dredging, construction, and agricultural, industrial, and municipal run-off (Colodey & Wells 1992, Santiago & Pelletier 2001, Lotze et al. 2006). Eel ...

Benthic habitat selection in juvenile European eel Anguilla anguilla: implications for coastal habitat management and restoration

“…Burrowing in the SV substratum was not observed in the present study, but elvers could use the same burrowing behaviours in the medium (MG) and large (LG) gravel as observed by Tomie et al . (). The authors indicate that A. rostrata commonly burrow in soft‐bottomed habitats, but also discuss a potential bias because the greater part of their study area consisted of soft bottom.…”

Survival and Habitat of Yellow‐Phase American Eels in North Carolina Tidal Creeks

“…) and their tendency to burrow (Glova ; Tomie et al. ). Taken together, our results indicate that development in tidal creeks and their watersheds in this region is not directly affecting the status of the American Eel.…”

Burrowing behaviour of the European eel (Anguilla anguilla): Effects of life stage

“…The sediment depth ranged from 5 cm for glass eels to 20 cm for yellow eels. This depth was chosen based on the maximum burrow depth of American yellow eels (Tomie et al ., 2013). All specimens were randomly introduced at a side of the aquarium.…”

“…Because eels in burrows respire water from the water column (Tomie et al, 2013), an increase in anoxic or hypoxic bottom waters could mean a loss of habitat.…”

“…Burrowing behaviour has also been observed among several Anguilliformes, which possess two mechanisms for burrowing: tail‐first and/or head‐first burrowing (De Schepper et al ., 2007a; De Schepper et al ., 2007b). Anguilla rostrata , e.g ., construct burrows head‐first (Tomie et al ., 2013). On the contrary, the spotted garden eel ( Heteroconger hassi Klausewitz & Eibl‐Eibesfeldt 1959) is an obligate tail‐first burrower, whereas the Indian snake eel ( Pisodonophis boro Hamilton 1822) can use both (De Schepper et al ., 2007a).…”