Sun-Compass Orientation in Mediterranean Fish Larvae

Abstract

Mortality is very high during the pelagic larval phase of fishes but the factors that determine recruitment success remain unclear and hard to predict. Because of their bipartite life history, larvae of coastal species have to head back to the shore at the end of their pelagic episode, to settle. These settlement-stage larvae are known to display strong sensory and motile abilities, but most work has been focused on tropical, insular environments and on the influence of coast-related cues on orientation. In this study we quantified the in situ orientation behavior of settlement-stage larvae in a temperate region, with a continuous coast and a dominant along-shore current, and inspected both coast-dependent and independent cues. We tested six species: one Pomacentridae, Chromis chromis, and five Sparidae, Boops boops, Diplodus annularis, Oblada melanura, Spicara smaris and Spondyliosoma cantharus. Over 85% of larvae were highly capable of keeping a bearing, which is comparable to the orientation abilities of tropical species. Sun-related cues influenced the precision of bearing-keeping at individual level. Three species, out of the four tested in sufficient numbers, oriented significantly relative to the sun position. These are the first in situ observations demonstrating the use of a sun compass for orientation by wild-caught settlement-stage larvae. This mechanism has potential for large-scale orientation of fish larvae globally.

Swimming speeds of Mediterranean settlement‐stage fish larvae nuance Hjort's aberrant drift hypothesis

“…Fish larvae are capable of swimming directionally in the ocean over short distances using coastal cues (Simpson et al ; Paris et al a ; Leis et al ) and there is increasing evidence that larvae can sense and orientate relative to coast‐independent cues, such as the position of the sun (Berenshtein et al ; Faillettaz et al ) or a magnetic compass (Bottesch et al ). In particular, the orientation abilities of six species tested here ( Boops boops , Chromis chromis, Diplodus annularis , Oblada melanura , Spicara smaris , and Spondyliosoma cantharus ) were investigated in the same location and time of the year (Faillettaz et al ). The vast majority of individuals (> 85%) followed a cardinal bearing while in blue waters and most used the sun's azimuth as a compass, suggesting a potential mechanism for large‐scale orientation in the open ocean that is particularly relevant for larval dispersal.…”

Larval Fish Swimming Behavior Alters Dispersal Patterns From Marine Protected Areas in the North-Western Mediterranean Sea

“…Orientation precision was set higher for large Sparidae (k = 4) compared to small Sparidae (k = 3.5). The values of k were estimated by fitting Von Mises distributions to the orientation bearings recorded for the two groups in Faillettaz et al, 2015).…”

“…Oriented swimming was initially thought to be limited to coastal areas, where larvae may use odor (Paris et al, 2013), sound (Simpson et al, 2005) or both to detect favorable settlement habitats (Teodósio et al, 2016). Increasing observations now suggest that fish larvae may also orient in the open ocean using coast-independent cues such as the position of the sun (Mouritsen et al, 2013;Berenshtein et al, 2014;Faillettaz et al, 2015) or even the magnetic field (Bottesch et al, 2016;O'Connor and Muheim, 2017). These empirical observations were carried out in several regions and environments: Australia (Leis et al, 2014), Taiwan , North Sea (Cresci et al, 2017), Mediterranean Sea etc.…”

Response of Gilthead Seabream (Sparus aurata L., 1758) Larvae to Nursery Odor Cues as Described by a New Set of Behavioral Indexes

“…The second premise postulates that once larvae sense estuarine cues, they will swim toward an estuarine ecosystem using distinct swimming strategies which vary according to their location (offshore areas with no influence of patchy estuarine cues, offshore or nearshore areas under the effect of patchy estuarine cues, estuarine plume, or near the entrance of an estuary). Larvae may also swim toward the coast when they are offshore and away from any estuarine cue as a result of an innate behavior (Faillettaz et al, 2015;Teodósio et al, 2016).…”

“…Potential larval stimuli include water pressure gradients (Burke et al, 1995), magnetism (Qin et al, 2015), visual (Whitfield, 1994;Faillettaz et al, 2015), auditory (Staaterman et al, 2014), and odor-based cues (McCormick and Manassa, 2008;Arvedlund and Kavanagh, 2009), which may be used in tandem to identify suitable habitats (Lecchini et al, 2005;Hale et al, 2008). These environmental cues will then trigger a variety of larval behaviors, such as orientation (Paris et al, 2013;Faillettaz et al, 2015), vertical migration (Fortier and Leggett, 1983), predator avoidance (Lehtiniemi, 2005), and habitat selection (Gerlach et al, 2007).…”