Small-scale patterns of deep-sea fish distributions and assemblages of the Grand Banks, Newfoundland continental slope

Demersal fish distribution and habitat use within and near Baltimore and Norfolk Canyons, U.S. middle Atlantic slope

“…The increasing rarity of complex habitat (seamounts excluded) and the decline of food quantity and quality with increasing depth argue against strong habitat association in deep environments where flexibility and opportunism might be more advantageous (Ross and Quattrini 2007). The lack of distinct fish and habitat associations below 1400 m (this study), > 800 m off Newfoundland (Baker et al 2012), and at 2836 and 3775 m in the western North Atlantic (Auster et al 1995) support that argument. However, Ross and Quattrini (2007) cautioned that more direct observations are needed, especially below mid-slope depths.…”

“…Although fish habitat association data continue to be lacking in the deep-sea (especially > 1000 m), emerging evidence suggests that fish associations with complex habitat on the mid to upper slope (< ~1000 m) can range from seemingly obligate (this study; Ross and Quattrini 2007;Quattrini et al 2012) to more opportunistic (this study; Costello et al 2005;Auster 2005;Baker et al 2012;Kutti et al 2014) to highly variable or not detectable (Biber et al 2014). Degree of associations may vary by region; however, in most areas of the slope there is an affinity for complex habitats, which may be expressed as differences in species composition, abundance patterns or both.…”

“…Corals and sponges provide relief, rugosity, and overall enhanced complexity (Miller et al 2012;BuhlMortensen et al 2010), but a cause/effect relationship between coral presence and fish assemblages remains elusive (Auster 2007;Baker et al 2012;Biber 2014). Slope fishes are commonly more abundant around reefs with corals (e.g., Costello et al 2005;Purser et al 2013), but the functional linkage to corals is unclear.…”

“…The most dramatic difference in fish assemblages in the Norfolk and Baltimore canyon study areas involved depth zonation where two quite different fish assemblages occurred deeper and shallower than 1400 m. A boundary for benthic fauna near 1400 to 1500 m is a common feature of the western North Atlantic (Musick 1979;Haedrich et al 1975Haedrich et al 1980Valentine et al 1980;Snelgrove and Haedrick 1985;Baker et al 2012), the North Atlantic in general (Koslow 1993), and perhaps globally (Gage and Tyler 1999;Carney 2005), but more continuous sampling across depths would better define boundaries and characteristics (sharp demarcation versus gradual faunal change). Mean bottom temperatures (4.0-4.3 °C) during the deepest dives (> 1400 m) were often 2-3 °C colder than shallower sites, were less variable, and coincided with the 4 °C isotherm that often denotes a deep-sea faunal boundary (Gage and Tyler 1999).…”

“…Some fishes appear to be restricted to complex habitats or may be drawn to processes (e.g., higher organic deposition) that are common in submarine canyons. For example, C. rupestris (Snelgrove and Haedrick 1985;Baker et al 2012) and several invertebrate taxa (Rowe 1971;Haedrich et al 1975) have been called regional "canyon indicator species" because they are found more frequently within canyons. Whether C. rupestris is a canyon indicator was less clear in our study.…”