Ecology of the Ocean Sunfish, Mola mola, in the southern California Current System

Abstract

The common ocean sunfish, Mola mola, occupies a unique position in the eastern Pacific Ocean and the California Current Large Marine Ecosystem (CCLME) as the world's heaviest, most fecund bony fish, and one of the most abundant gelativores. M. mola frequently occur as bycatch in fisheries worldwide and comprise the greatest portion of the bycatch in California's large-mesh drift gillnet fishery. In this first long-term tagging study of any ocean sunfish species in the eastern Pacific, 15 M. mola (99 cm to 200 cm total length) were tagged in the southern California Bight (SCB) between 2003 and 2010 using 14 satellite pop-off archival tags (PATs) and one Fastloc Mk10 GPS tag. Ten tags provided positional data for a cumulative dataset of 349 tracking days during the months of July through March. Thirteen tags provided temperature and depth data. All M. mola remained within~300 km of the coast, and nearly all exhibited seasonal movement between the SCB and adjacent waters off northern and central Baja California, Mexico. No tagged individuals were tracked north of the SCB. Tag depth data showed diel vertical migration and occasional deep (N500 m) dives. Data from the Fastloc GPS tag allowed close examination of the relationship between the movements of the largest tagged ocean sunfish (2 m TL) and fine-scale oceanographic features. Near-instantaneous satellite sea surface temperature images showed this individual associated with upwelling fronts along its migration path, which exceeded 800 km and ranged from 6 to 128 km from the coast. Tag depth data showed active use of the water column within the frontal zones. Synthetic aperture radar (SAR) images demonstrated that surface slicks, which often indicate convergent circulation, coincided with this type of front. Zooplankton tows in the southern region of tracking off central Baja California, Mexico revealed dense populations of salps toward the warm side of these fronts. Satellite tag and ecosystem data suggest that bio-physical interactions in coastal upwelling fronts create favorable foraging habitat.

Environmental influence on the seasonal movements of satellite-tracked ocean sunfish Mola mola in the north-east Atlantic

“…Likewise, the preference for frontal regions, also apparent in our model, has been described for other predators in the same geographical region as this study, linked to increased abundance of prey and thus, enhanced foraging opportunities [9, 51, 60]. Furthermore, our results confirm previous observations in the north-east Atlantic [42] and more recently in the Pacific, where sunfish were associated with upwelling frontal regions [61]. Animal movements are expected to be driven by environmental suitability to satisfy the species intrinsic demands, such as feeding, which in turn is motivated by the abundance of prey [e.g.…”

Motes enhance data recovery from satellite-relayed biologgers and can facilitate collaborative research into marine habitat utilization

“…One type is known as pop-up archival tags (PATs) and is predominantly used to track largescale movements of marine animals at sea, especially those that do not break the surface or where there is no rigid surface for tag attachment (e.g., most teleost fishes [11,34,39]). The data collected by these tags are often several weeks old when they are transmitted to satellite, and position estimates between the release site and the pop-up site are based on light-based geolocation methods using light levels measured and stored by the tag [31].…”

New and historical records of the ocean sunfish Mola mola in Icelandic waters

“…This could possibly be a part of a seasonal migration of the species into the northern part of the North Atlantic Ocean (Sims & Southall, ; Sims et al , ). Mola mola is now known to be a more active swimmer than previously thought (Pope et al , ; Thys et al , ); nothing is known, however, about their seasonal long‐distance migration into North Atlantic Ocean waters south of Iceland and it is not known if these fishes originate from the eastern or western Atlantic. The beached records extend into early winter; however, because the carcass condition is usually unknown, it is not possible to state with any certainty when the fish may have been alive in nearby waters.…”