Giant jelly eaters on the line: Species distribution and bycatch of three dominant sunfishes in the Southwest Pacific

Abstract

The ocean sunfishes have a long and confusing taxonomic legacy, clouding the global zoogeography of each species and hindering fisheries bycatch assessments. The traditional view of Mola mola as the most common sunfish species worldwide is challenged by our findings from Australia and New Zealand, revealing that three large sunfishes, Masturus lanceolatus, Mola alexandrini and Mola tecta, dominate the tropical/subtropical, warm-temperate and coldtemperate waters here, respectively, while Mola mola-both Pacific and Atlantic clades-is relatively rare. These findings were based on phylogenetic (mtDNA D-loop) and/or morphological species identification of sunfish from longline bycatches (n = 106), natural history museum collections (n = 45) and other sources (n = 12), informed by recent advances in the taxonomy of the genus Mola. Furthermore, separation in species distributions were seen when comparing sampling latitude and sea surface temperature. The findings imply that the longline fisheries observer sunfish data from Australia and New Zealand is a mix of species, and not dominated by M. mola as previously assumed. Mean catch per unit Effort (2001-13) in 1° latitude/longitude grids off Pacific Australia and New Zealand were predominantly < 1 sunfish.1,000 hooks-1 (up to 6.5 in some areas) with no statistical significant upwards or downwards trends detected over time in four fishing ground subareas, each presumably dominated by either Masturus lanceolatus, Mola alexandrini or Mola tecta. Widespread specimen identification errors had previously obscured a more complex Molidae zoogeography in the area, highlighting that phylogenetic analyses of sunfish bycatch globally would benefit species-level conservation status evaluations. 1 Introduction The ocean sunfishes (genera Mola and Masturus, Family Molidae) are a somewhat overlooked group of large teleosts, infamous for their odd shape resembling 'swimming heads' without tails, and for including the world's heaviest bony fish (Sawai et al. 2018). They are difficult to study, but with the advances in modern technology they have experienced a surge in research in recent years, revealing they are not the peculiar, sluggish oddities of nature they have traditionally been considered (e.g. Cartamil and Lowe, 2004; Watanabe and Sato, 2008). Instead, their diet and evidently high numbers worldwide suggest they play an important ecological role as predators of gelatinous zooplankton (Breen et al. 2017; Grémillet et al., 2017; Phillips et al. 2017). Advances in telemetry, digital imagery and other technologies continue to confirm that ocean sunfish are active predators, hunting at depth in dynamic frontal systems (Nakamura et al. 2015; Thys et al. 2015; Sousa et al. 2016a, b). However much of their life history is still unknown, as is the global zoogeography of all taxa in the family. including the generic use of M. mola, are also common in longline fisheries in other parts of the world (e.g.

Species identification of sunfish specimens (Genera Mola and Masturus, Family Molidae) from Australian and New Zealand natural history museum collections and other local sources

“… M. mola M. alexandrini PHYL : JNSW-2 in [10] (D-loop: AB439109). Also in [1] , [7] , [8] . AMS I.41536-001 , 178 cm TL, tissue & photographs, Narrabeen Beach, NSW (35.716°S 151.300°E), found alive in shallow waters in poor condition (euthanized), 11 September 2002.…”

“… M. mola M. tecta PHYL: NNSW-1 in [10] (D-loop: AB439108). Also in [1] , [7] , [8] . Submission to BOLD by AMS (CO1 sequence ID: AMS174-08), phylogenetic analysis in [6] .…”

“… M. ramsayi M. alexandrini PHYL: [6] (D-loop: MF158140; CO1: MF158118). Also in [1] ) (D-loop). NMNZ P.057679 e , holotype, 101.1 cm TL, wet specimen (tissue P.057679/TS3 ), male, North Taranaki Bight, west coast of North Island, NZ (38.425°S 174.150°E), trawl, 78 m, 25 December 2015.…”

“…nov. M. tecta PHYL : [6] (D-loop: MF158147; CO1: MF158119). Also in [1] ) (D-loop). NMV 32054 , large, mounted skeleton, Port Phillip Bay, Hobsons Bay, VIC (37.850°S 144.930°E), 1879.…”

“…References to phylogenetic analyses, where applicable, are included. The summary was collated in support of publication Giant jelly eaters on the line: species distribution and bycatch of three dominant sunfishes in the Southwest Pacific [1] .…”