Deep-Sea Research I 64 (2012) 78–85 Contents lists available at SciVerse ScienceDirect Deep-Sea Research I journal homepage: www.elsevier.com/locate/dsri Distinguishing between the abyssal macrourids Coryphaenoides yaquinae and C. armatus from in situ photography A.J. Jamieson, I.G. Priede, J. Craig n Oceanlab, Institute of Biological and Environmental Science, University of Aberdeen, Main Street, Newburgh, Aberdeenshire AB41 6AA, UK article info abstract Article history: The scavenging fish communities at abyssal depths of the Pacific Ocean are dominated by two species Received 16 November 2011 of macrourids; the rough abyssal grenadier Coryphaenoides yaquinae Iwamoto and Stein, 1974 and the Received in revised form abyssal grenadier C. armatus (Hector, 1875). These two species are morphologically very similar, and in 24 January 2012 the absence of physical specimens are notoriously difficult to distinguish from photographic data. In an Accepted 13 February 2012 era of increasing reliance on imaging technology in the deep sea, we provide an analysis of images of Available online 21 February 2012 the two species from around the Pacific Rim with supplementary data from the Atlantic and Southern Keywords: Oceans. Our results show that image-specific morphometric characters are inadequate to distinguish Baited camera the two species. However, the way in which artificial illumination is reflected from the body is both Species identification sufficient, and consistently different to distinguish between the two species. The results are also Macrouridae corroborated by known geographic and bathymetric distributions. This analysis is intended to provide a Abyssal zone Pacific Ocean reliable method of identification from deep-sea imaging systems in the absence of standard fishing techniques. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction plains. In the Pacific Ocean, the closely related congener, C. yaquinae, dominates abyssal depths as a result of metabolic The scavenging fish community at abyssal depths of the world adaptations for life in a comparatively oligotrophic region, free of oceans are dominated by the macrourids (or grenadiers). The competition, yet is absent in the North Atlantic despite similar abyssal plains of the Pacific Ocean are dominated by the rough depth, low temperatures and oligotrophic setting. Coryphaenoides abyssal grenadier Coryphaenoides yaquinae Iwamoto and Stein, yaquinae is confined to the Pacific, where it dominates under the 1974. The cosmopolitan abyssal grenadier Coryphaenoides arma- vast expanse of the central gyres and is known to inhabit a depth tus (Hector, 1875) is ubiquitous across the Atlantic, Southern and range of 3400 to 5800 m (Wilson and Waples, 1983). Therefore, Indian oceans, and the deep continental slopes and rises of the there is a small depth range of 900 m (3400–4300 m) where the Pacific Rim. Both species are readily attracted to bait, often in two species co-exist on the Pacific continental slopes but are large numbers, which has resulted in these two species being the generally bathymetrically segregated (Endo and Okamura, 1992). subject of both numerous and diverse scientific investigations for The role of C. yaquinae as the deeper of the two species is evident decades (e.g. Smith, 1978; Armstrong et al., 1991, 1992; Priede in more recent samples reported from 6380–6450 m (Endo and and Smith, 1986; Smith et al., 1992; Collins et al., 1999; Bailey Okamura, 1992) as well as photographic and video observations et al., 2002; Drazen, 2002; Barry and Drazen, 2007; King and from 6160 m and 6945 m (Horibe, 1982; Jamieson et al., 2009c, Priede, 2008, Yeh and Drazen, 2011). respectively). Upon reviewing the two species, Wilson and Waples (1983) These two species are notorious for being almost indistin- concluded that C. armatus is a wide-ranging, mostly eutrophic, guishable from one another based on external morphology as deep-slope/upper-rise species which dominates the abyssal reported by Wilson and Waples (1983, 1984) who highlighted regions of the Atlantic and Indian Oceans between 2000 and erroneous identification by others such as Pearcy et al. (1982), 4800 m. However, in the Pacific Ocean, it is restricted to relatively Stein and Pearcy (1982); Smith et al. (1979). Coryphaenoides food-rich environments between 2000 and 4300 m, unable to yaquinae and C. armatus are very closely related and easily penetrate into the large oligotrophic expanses of the abyssal confused and, for a period, thought to be the same species (Iwamoto and Stein, 1974). In the presence of physical and comparative specimens, C. yaquinae and C. armatus can be n Corresponding author. Tel.: þ44 1224 274440. distinguished by differences in the number and arrangement of E-mail address: [email protected] (J. Craig). premaxillary and mandibular rows of teeth, or by DNA barcoding. 0967-0637/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr.2012.02.001 A.J. Jamieson et al. / Deep-Sea Research I 64 (2012) 78–85 79 In addition, the two species differ in the mean number of ventral examine how to distinguish C. yaquinae from C. armatus in fin rays, mean number of first dorsal soft rays and in the ranks of instances of co-inhabitation. The approach was to examine; values of orbital length/head length (Wilson and Waples, 1983). (1) Whether image-specific morphological measurements could Iwamoto and Stein (1974) also noted differences between be made to determine species identification, (2) Whether the C. armatus and C. yaquinae in squamation and coloration. They physical appearance is sufficient to distinguish the two species, reported differences in scale morphology and the degree of scale- (3) whether the artificial illumination from the lander vehicle less area on the anterolateral regions of the snout. However, alters the appearance of fish at certain distances and (4) whether Wilson and Waples (1983) reported wide variation in squamation the results could be corroborated by the known bathymetric and features, and rather showed electrophoretic differences between geographic distribution of the species. the two species. However, all these methods rely on obtaining physical specimens for examination. In an age where scientific endeavour is pushing more regularly 2. Materials and methods into deeper waters, there is a heavier reliance on still photo- graphy and video. When undertaking biological surveys in the All still photography taken in the Pacific Ocean was to hadal trenches (6500–11,000 m deep), this reliance is exacerbated obtained using Hadal-lander B (Jamieson et al., 2009a) with one in that most research vessels do not carry sufficient wires to tow supplemental video from Hadal-Lander A in the Japan Trench bottom trawls or epibenthic sledges. In the absence of wire (Jamieson et al., 2009bc). Hadal-lander B was a free-falling lander deployed sampling, free-falling lander vehicles equipped with equipped with a 5 megapixel digital still camera (OE14-208; baited cameras and/or traps have been regularly used in research Kongsberg Maritime, UK). Illumination was provided by a single campaigns as an alternative to net sampling (Jones et al., 2003; flashgun (OE11-242; Kongsberg Maritime, UK) which has a light Bailey et al., 2007; Yeh and Drazen, 2009, 2011; Jamieson et al., output of 80 W maximum and a beam angle of 551. On the Hadal- 3 2011). One such campaign, the HADEEP project (2006–2011; lander, the flash output is set to /4, (60 W). The camera was Jamieson et al., 2009a), obtained video footage and still images mounted vertically at an altitude 1 m above the seafloor provid- À2 of bait-attending fish from the Japan, Kermadec and Peru-Chile ing a visible area of 62 Â 46.5 cm (0.29 m ). In the centre of the trenches with additional data from the Mariana abyssal plains field-of-view was a parcel of bait (1 kg of tuna or mackerel). (Jamieson et al., 2009c, 2011; Fujii et al., 2010). One of the A 1 cm diameter scale bar was also in the centre of the field of components to these studies was the investigation into the view, positioned to intersect the sediment-water interface upon geographic and bathymetric distribution of hadal fishes. In order landing. Time-lapse images were taken at 60 s intervals. The to examine these patterns (as well as those of other taxa), Hadal-Lander A had a 3CCD colour video camera arranged in comparative sampling was required to take place on the sur- the same way as Hadal-Lander B and programmed to take 1 min rounding abyssal plains to either prove or refute hadal or trench of footage every 5 min. Illumination was provided by two 50 W endemism, and to determine the lower bathymetric limits of fish halogen bulbs also positioned at 1 m above bottom. To permit species. In the trenches, the fishes present were primarily found comparison with Atlantic and Southern Ocean data, images from to be liparids inhabiting depths of 6900–7700 m (Fujii et al., the ROBIO lander were used (Jamieson and Bagley, 2005). The 2010). ROBIO and Hadal-Landers use the same camera and flash system On the abyssal plains that surround the hadal trenches, the and differ only in camera altitude above bottom; Hadal-Land- bait-attending fish communities are comprised of both Coryphae- er¼1 m above bottom, ROBIO¼2 m above bottom. noides yaquinae and C. armatus. Whilst these species can be The landers descended to the seafloor by virtue of negatively readily distinguished by either genetics or certain morphological buoyant ballast weights. At the end of the experimental period characters, such determinants of species are not measureable in the ballast was jettisoned by acoustic command from the surface. photographic images. Baited cameras, and other methods of All images were obtained autonomously and upon retrieval, all in situ imaging (e.g. Bailey et al., 2006), are disadvantaged in their imaging data were downloaded.