Abstracts

Giorgio Carnevale | Evolution and Fossil Record of the Ocean Sunfishes

Little is known about the evolutionary history of the Molidae because of the fragmentary and largely incomplete fossil record of this morphologically peculiar group of tetraodontiform fishes. The majority of fossils referred to in this family consist of isolated jaws and dermal plates, although a few articulated skeletons are also known. The scarcity of fossils belonging to the Molidae seems to be related to the overall considerable reduction of the bony tissue in the skeleton, with the bones being weakly ossified and characterized by a delicate fibrous or spongy texture. The earliest rare representatives of this family date back to the middle Eocene, while the crown group Molidae appeared in the record no later than the Early Miocene. This talk illustrates the known fossil record of molids and discusses the phylogenetic relationships between the fossil and extant taxa, and the potential evolutionary drivers that contributed to their diversification.

Etsuro Sawai | Largest Size Records and Taxonomic History of Modern Ocean Sunfishes (Molidae)

Ocean sunfishes (family Molidae) have attracted the interest of people for centuries because of their unique shape (a complete lack of a caudal fin) and large size [> 3 m total length and > 2,000 kg body weight]. The study of molid morphology and taxonomy dates back to at least the 16th century and encompasses a long legacy of taxonomic confusion. In recent years, due to the development of genetics, the taxonomy of modern ocean sunfishes has greatly advanced. Currently, the family Molidae has five valid species: slender sunfish Ranzania laevis (Pennant 1776), sharptail sunfish Masturus lanceolatus (Liénard 1840), hoodwinker sunfish Mola tecta Nyegaard et al. 2017, giant sunfish Mola alexandrini (Ranzani 1839), and ocean sunfish Mola mola (Linnaeus 1758). Here we review the largest size records and taxonomic history, for progressing the taxonomic understanding of ocean sunfishes (adult to senescent stage) in the future.

Marianne Nyegaard | Hood-winking as an Artform: Mola tecta Surfaces in the Californian Current System

The first ever report of a Hoodwinker sunfish (Mola tecta) in California in 2019, less than two years after the species was first described in New Zealand, came as a surprise. Mola tecta was thought to be a temperate southern hemisphere species with the warm equatorial waters presenting a major barrier to its distribution. However, subsequently numerous hoodwinkers have “surfaced” in the Pacific Northwest. Although the ocean sunfish (Mola mola) is by far the most common Mola species in the Californian current system, our preliminary results indicate that Mola tecta also has a presence here beyond infrequent, chance occurrences. To better understand its spatial extent, our study relies on citizen science, media reports and social media to collect and curate sunfish photos from California to Alaska, from which we map species level occurrences. Our aim is to understand how common Mola tecta is in this area, relative to Mola mola, and (through genetic analysis) examine the connectivity with Mola tecta populations in South America and New Zealand. Our method has limitations however, and in addition to our preliminary results, this presentation also includes a brief review of practical ways – and pitfalls – to identity Mola species from photos.

Tierney Thys, Eric Caldera, Marianne Nyegaard, Jonathan Whitney | Genetic Insights Regarding Taxonomy, Phylo-geography and Evolution of Ocean Sunfishes: Roundtable discussion with slides

We review the taxonomy, phylogeography and evolutionary history of the molids (Tetraodontiformes: Molidae), focusing on the contributions provided by molecular genetics. Studies using the mitochondrial genome have confirmed the phylogenetic topology of the Molidae genera hypothesized from morphological studies (Ranzania-basal, Masturus-intermediate, Mola-derived). Mitochondrial DNA identified a Mola clade that subsequently facilitated the description of M. tecta, the first novel molid species in over 125 years. To resolve the taxonomy of the ocean sunfish (M. mola) and the bump-head sunfish (M. alexandrini) we sequenced the hypervariable mitochondrial d-loop region and conducted phylogenetic analyses on a population of molids from Ceuta, Spain that possesses both a bump-head and a trait unique to M. mola—the wavy clavus. In addition, we sequenced Mola and Ranzania spanning the Pacific and Atlantic Ocean basins to assess phylogeographic structure within these taxa. Bump head, wavy clavus Ceuta molids were genetically identified as M. mola, supporting a proposed change of the “bump-head” common name to simply giant ocean sunfish. Atlantic and Pacific molids mostly grouped into respective geographic clades, but further population genetic studies are needed to tease out patterns of gene-flow and distribution. To that end, we summarize the numerous genetic and genomic tools available to inform molid biology and monitoring efforts moving forward. Lastly, we discuss the genome contents and patterns of selection in the recently sequenced Mola mola genome.

Tierney Thys, Marianne Nyegaard | Ocean Sunfish Larvae: Detections, Identification and Predation

While ocean sunfishes hold the vertebrate record for having the most ova in a single female, information on the natural history of their larvae and juveniles has yet to be collated. Our research includes the most comprehensive compilation of larval molid records to date, and places the records within a global spatial context. Gathered from natural history museum collections, modern ichthyoplankton sampling efforts and historical records dating back to the 1800s, a total of  452 records were collected comprising 9,770 larvae in total: 285 Masturus, 84 Mola spp., 61 unspecified Molidae and 9,340 Ranzania (340 of which were eggs). Larval stages of early development for each molid genera are identified, described, and illustrated with original drawings.  Larval records also include larvae extracted from the guts of 26 different predator species: 17 large pelagic piscivorous fishes from six families, and nine seabird species from five families. While this ongoing work cannot be considered an exhaustive compilation of all molid larval knowledge, it does provide a foundation on which to build a more extensive molid larval database. It also underscores the importance of collecting hydrographic metadata to accompany each record. We hope that future studies can use this research to help locate additional spawning sites and achieve the critical mass of data required for habitat suitability modelling.  Such a vantage point would allow an assessment of how spawning sites may be impacted by ongoing environmental and anthropogenic changes and inform management plans.

Marko Freese  | Larval Distribution of the Ocean Sunfishes Ranzania laevis & Masturus lanceolatus in the Sargasso Sea Subtropical Convergence Zone

Sunfishes (Molidae) are an iconic and a comparably prominent family of fish, yet details about the reproductive biology of its five known species are fairly unknown. While sunfish larvae have been found in different places around the globe, only few studies have focused on learning more about their larval ecology and recruitment mechanisms. Nevertheless, already 100 years ago, Danish researcher Johannes Schmidt had reported catches of small sunfish larvae during his famous Dana expeditions into the central Atlantic to find the spawning areas of Atlantic anguillid eels. Between 2011 and 2017, the German Thünen Institute of Fisheries Ecology conducted a series of multi-purpose research cruises into the central Sargasso Sea to collect information about hydrographical and ecological conditions of the alleged spawning grounds of Anguilla anguilla and Anguilla rostrata. During two of these expeditions, between March and April 2014 and 2015, a total of 999 (2014) and 383 (2015) sunfish larvae were collected with 100 hauls in an area of around 400 000 nautical miles2. Larvae were subsequently measured and morphologically as well as genetically identified. The vast majority (>96%) of caught Molidae larvae was represented by the Slender sunfish (Ranzania laevis), while the remaining fraction (<4%) was identified as Sharptail mola (Masturus lanceolatus). Ranzania larvae were recorded in a broad size range measuring from 0.76 to 9.135 mm preclaval length (PCL), while Masturus larvae were mostly larger (2.13 to 17.76 mm PCL). Data on abundance and distribution in the research area in both datasets revealed that Ranzania larvae were caught primarily inside and south of a thermal frontal zone with increasing abundances toward warmer surface layers in the southeast of the study area. In contrast, Masturus larvae were evenly distributed with no obvious hydrographic preferences. While our results suggest Masturus to spawn at a different time or place than Ranzania due to its low abundance, more advanced development and unequal spatial distribution, the consistent presence of very small, freshy hatched Ranzania larvae confirm the Sargasso Sea as a spawning area for R. laevis throughout the month of April.

Tom Doyle  | Evidence of a Range Expansion in Sunfish from 47 Years of Coastal Sightings

What we know about fish abundance mostly comes from fisheries survey data. However, for ocean sunfish (Mola spp.), we know almost nothing about their historical abundance as they are rarely targeted. Yet, due to their unusual morphology, fecundity, large size and diet, understanding their past abundance is important as they represent one of the most ecologically and functionally distinct fish taxa in our seas and therefore may be a useful indicator of change. Within this context, here we provide the first long term index of ocean sunfish abundance derived from observations made from a coastal bird observatory over a 47-year period. Using a GLM with a hurdle to model trends in sunfish data and deal with imperfect detectability, we found that there was a higher probability of detecting a sunfish in the 1990s and 2000s than at any other time period at the observatory. In terms of environmental variables, the annual mean position of the 13°C sea surface temperature isotherm was significantly correlated with the probability of detecting a sunfish. Analysis of the Continuous Plankton Recorder siphonophore abundance data showed a dramatic increase during the late 1990s and especially in the 2000s, yet there was a weak negative association with the probability of detecting a sunfish. Our results suggest that the increase in sunfish in the Celtic Sea may have been triggered by an increase in temperature and subsequently as sunfish expanded their range it is likely that they benefited from this increase in food availability.
 

Miguel Baptista  | Length-weight Relationships of North Atlantic M. mola and Future Research on Mola spp. in the Northeast Atlantic

In this talk, we present length-weight relationships (LWR) for North Atlantic Ocean Mola mola and compare them with LWR data from previously reported North Pacific M. mola. We also outline four questions for future research: 1) Are there sub-populations of Mola spp. along a latitudinal gradient in the northeast Atlantic? ; 2) What is the relative distribution of Mola species in the northeast Atlantic?; 3) Do all Mola spp. in the northeast Atlantic share a common spatial origin (spawning ground)? and lastly; 4) Can abundance and population size be estimated from bycatch data of tuna set-nets?

Kate Bemis | Comparative Anatomy and Ontogeny of Ocean Sunfishes (Tetraodontiformes: Molidae)

Although ocean sunfishes (Molidae) have been studied for more than 500 years, their anatomy remains incompletely known and needs to now be reconsidered in light of advances in molid ecology. This synthesis will serve as a basis for future studies of the comparative anatomy of these unique fishes. This talk explores the comparative anatomy of sunfishes to examine general body form, external anatomy, and organ systems, with the exception of muscular and reproductive systems that are covered elsewhere in this symposium. Many ontogenetic changes occur in molid anatomy, which will be highlighted in this talk. Molid anatomy is on one hand simplified and marked by loss, fusion, and reduction of elements, while at the same time displays a range of specializations aligned with overall life history.

John Davenport | Locomotory systems and Biomechanics of Ocean Sunfish

The unusual appearance of ocean sunfish and their relatives (Molidae), featuring exaggerated dorsal and anal fins and a missing caudal fin, raises the question of how they swim. In this presentation, the locomotory systems and biomechanics of ocean sunfish are reviewed based on recent morphological, kinematic, and behavioral studies. Ocean sunfish flap their dorsal and anal fins laterally to produce lift-based propulsion forces, a unique swimming style in which two fins with different origins function as paired vertical wings. The two fins are symmetrical within individuals, despite ontogenetic changes in shape. Unlike most other teleosts that have axial musculatures which drive caudal fins, sunfish have two sets of muscles, separated by a thick horizontal septum. These muscles run dorso-ventrally to drive the dorsal and anal fins. Aerobic red muscles are located medial to anaerobic white muscles, an arrangement reminiscent of endothermic (i.e., high body temperature) fishes, although sunfish are apparently ectothermic. The thick, white sub-skin layer (hypodermis) has definite exoskeletal and probable buoyancy functions (adult Molidae lack a swim bladder). It is suggested that their conspicuous swimming style and associated morphology enable energy-efficient swimming at a cost of reduced acceleration and maneuvering abilities, allowing sunfish to search the open ocean for patchily distributed prey (e.g. gelatinous zooplankton).

Tasha Phillips | Jellies, Jaws and a Giant Appetite; Revealing the Surprising Diet of the Ocean Sunfish

Exploring what a fish eats provides important insights to scientists and conservationists, shining a light on fish behavior, habitat-use and ecosystem role. For the ocean sunfishes, people have long thought this group only ate jellies. More recent evidence reveals their diet is much more interesting. Scientists have discovered that ocean sunfish change their diet as they grow larger, with the smaller sunfish eating a wide range of prey (crustaceans, molluscs, even fish). They can even also take on predatory and scavenging roles. As they grow into oceanic giants, they focus more heavily on jellies and other gelatinous prey. Remarkably the biggest fish (up to 3m in length) appear to survive primarily on jellies. In this talk, we describe methods for revealing the mysterious diet of these ocean oddballs, highlight their dietary shifts and explore how the biggest of the bony fishes manages to survive on a diet of jelly.

Lara Sousa | Movements and Foraging Behaviour of the Ocean Sunfishes

Widespread across tropical and temperate seas, the movements of ocean sunfish species have been tracked remotely with satellite telemetry since the year 2002. Likewise, advancements in animal borne sensors and cameras have provided previously intractable insights into their foraging ecology. Within this broader context, this talk focuses on two main elements: (1) sunfish horizontal and vertical tracked movements at different spatial scales and, (2) seasonal shifts in distribution linked to habitat productivity and water temperature. Physiological mechanisms which may enable sunfish to forage extensively are explored, such as how the large size of adult sunfish (with their thick hypodermal tissue layer) influence foraging abilities during deep dives to below 500 m. Lastly, we make recommendations for future work, highlighting the need for satellite tracking studies outside of coastal regions; tracking molid species other than M. mola and M. alexandrini; and the monitoring of a wider range of individual sizes, especially larger mature sunfishes. These three major points are key to gaining a clearer understanding of Mola spp. movements and distribution patterns worldwide, while shedding light on reproduction ecology.

Martin Arostegui | Spatiotemporal Segregation of Ocean Sunfish Species (Molidae) in the Eastern North Pacific

Ocean sunfishes or molas (Molidae) are difficult to study as a result of their extensive movements and low densities in remote waters. In particular, little is known of the environmental niche separation and differences in the reproductive or movement ecology of molids in sympatry. We investigated spatiotemporal dynamics in the distribution of the common mola Mola mola, sharptail mola Masturus lanceolatus, and slender mola Ranzania laevis in the eastern North Pacific. We used observer data from a commercial fishery consisting of 85 000+ longline sets spanning 24 yr, >50 degrees in longitude, and >45 degrees in latitude. Satellite altimetry analysis, species distribution modeling, and multivariate ordination revealed thermal niche separation, spatiotemporal segregation, and distinct community associations of the 3 molid species. Our quantitative findings suggest that the common mola is a more temperate species, while slender and sharptail mola are more (sub)-tropical species, and that slender (and possibly also sharptail) mola undergo spawning migrations to the region around the Hawaiian Islands. In addition, we identified potential effects of fishing gear type on molid catch probability, an increasing trend in catch probability of a vulnerable species perhaps related to a shift in the distribution of fishing effort, and the possible presence in the fishery of a fourth molid species being misidentified as a congener, all of which are important conservation considerations for these enigmatic fishes.

Joao Correia  | Mola mola Collection and Transport

Since 2006 Flying Sharks has shipped oceanic sunfish, Mola mola, to nearly one dozen institutions throughout the world, including countries as far as Russia, China, Singapore, Dubai, and USA, among closer European countries, such as Germany and Denmark. While the initial animals were collected in the southern region of Portugal, Algarve, in cooperation with a commercial fishing company that operates a set-net, from 2017 onwards animals started being collected off the Portuguese western shore, specifically in Peniche, with the assistance of commercial fishermen operating purse seiners, traditionally targeting schooling fish. More recently even, animals are being hand caught by a diving operation’s zodiac. This created a wide suite of operational difficulties, such as devising the proper way to retrieve them from the ocean untouched. Difficulties were found in land as well, since the Peniche holding facility was initially not equipped to deal with such large animals and water quality was less than optimal. Multiple filtration solutions were adopted to deal with these aspects.

Hugo Batista | Growth and Feeding Strategies of Mola mola

The Ocean sunfish (Mola mola) is an enigmatic species, with many aspects of its biology and life cycle still requiring further investigation and understanding. Its nutritional requirements are a central topic of interest, as feeding strategies are key to ensure good husbandry practices. Fine tuning their diet regime should promote captive specimens’ overall condition and growth. There are different management methods being applied from various institutions over the world and while some maintain a consistent percent BW per day ration, others apply an adjusted percentage according to the animal’s development. Across institutions, BW percentages offered daily, vary from 5-6% at early stages to less than 1% for over 100Kg animals, distributed in one to six meals per day. Combining data from wild sunfish diet research and food consumption rates collected from captive animals we present key factors to define a feeding regime specific for this species. Institutions must not assume that one rule fits it all as there are important factors to consider. Aquarium systems, animal’s condition and metabolism also impact the feeding regime and thus, must be evaluated continuously to apply the best practices to enhance longevity of these animals on display.

Michael Howard | Data Sets Guide Ocean Sunfish Husbandry and Animal Care Research Programs

Collection of basic data is integral to science. Aquarium sciences rely on historical data (biotic and abiotic) to set the foundation for continued success while providing context for overall species management. When working with a challenging and under-studied species like the ocean sunfish, Mola mola, a strong commitment to data collection underscores a well-managed program.  Here we will highlight how long-term data sets such as water parameters, consumption and growth rates from public aquariums may clarify and inform key components of sunfish husbandry. Hopefully, data and ongoing research efforts at public aquariums will lead to improved animal welfare while supporting current and future aquarium, laboratory and in situ field studies.

Ana Elena Ahuir  | Parasites of Ocean Sunfishes

Family Molidae are some of the most heavily parasitized fish worldwide, however there is scarce information regarding the effects of the parasite fauna in the health of these fishes. Knowing their parasites can provide information about insights dietary choices, and even population connectivity. In this talk, the parasitic fauna of ocean sunfishes is reviewed including a checklist with parasite location and localities. Sixty-six parasitic species are reported from Mola mola, 17 from M. alexandrini, five from Masturus lanceolatus, and three from Ranzania laevis. The existence and benefits of parasitic cleaning events are also discussed. The baseline research reviewed herein provides essential groundwork for identifying and addressing existing knowledge gaps and pursuing fruitful future research, including parasitological studies in M. tecta.

Miguel Baptista and Cátia Figueiredo | Biotoxins, Trace Elements and Microplastics in the Ocean Sunfishes (Molidae)

Any substance may become a contaminant when occurring at a significantly higher concentration than the natural background level in a particular area or organism. One major concern regarding contaminants is their persistence in the marine environment and subsequent accumulation in seawater, sediments and biota. Due to public health concerns, research on the accumulation of contaminants in marine fish is chiefly conducted on economically important species. Since ocean sunfishes (Molidae) have a low commercial value worldwide, this group has been mostly overlooked. The available data on the presence of three types of contaminants (biotoxins, trace elements and microplastics) in ocean sunfishes, primarily Mola spp., is presented. Evidence indicates Mola spp. and Masturus lanceolatus do not contain tetrodotoxin. Ocean sunfish exhibit a selection of trace elements (e.g., As, Cd, Hg, Pb, Zn) that vary with tissue, sex, size, season and location. Species differences in elemental content also exist between Mola spp. and M. lanceolatus. Lastly, microplastic has been found in the stomach contents of 79% of Mola spp. individuals examined thus far. While providing an overview of available information on the presence of contaminants in Molidae, this work showed an overall deficit of information and further research in this topic is recommended.

Tierney Thys and Kristy Forsgren | Reproductive Biology of the Ocean Sunfishes

The circumglobal ocean sunfishes, Molidae (specifically Mola spp.), have long held the record for being the world’s most fecund vertebrates. This record is based on one 1.5m individual whose ovary was estimated to contain 300 million “small and unripe” ova (Schmidt 1921). Few data have been available to assess this claim of reproductive prowess since large gravid sunfishes (>1.5m TL) are rarely encountered and ways of describing fecundity are not standardized. This talk reviews our current knowledge of sunfish reproduction and proposes an assessment of fecundity in terms of productivity. It offers additional insight through the histological examination of samples collected from geographically disparate regions including California and Japan, the east coast of the USA, and the Mediterranean (Italy and Portugal). Ovaries at different stages of sexual maturity from two different species of molid  are examined--M. mola (35.5cm - 2.9m TL) and M. tecta (2.15m TL). From Kamogawa Japan, three additional large female Mola spp. (2.10m, 2.43m and 2.72m TL) are described along with the first known molid egg release from a 1m TL captive female at Kamogawa SeaWorld. A new record of 847 million ova in a single female (2.2m total length) is presented. Lastly, future research directions are detailed and discussed. 

Rich Dolan | Marine Art as Universal Language

In this talk I describe a visual showcase titled Tails of Stellwagen that displays sculptures of marine fauna for educational outreach via museums and naturalists. The arts hold value in elevating the beauty and essence of the natural world. The motivation of this artwork is to promote literacy in conservation and marine biology for an audience diverse in culture, language, and sensory abilities. The durability of each sculpture enables an educator to use visual language while on boats or in the field. Scaled-down replicas represent species often too large for live display in most aquariums and museums. The complex feeding behaviors and physiology of whales are explained through articulated models. while the perplexing nature of ocean sunfish is simplified in models that are detailed and anatomically accurate. 

Marianne Nyegaard  | Fisheries Interactions Distribution Modelling and Conservation Issues of the Ocean Sunfishes

Among marine megafauna, the large species of ocean sunfish (genera Mola and Masturus) are atypical. Specifically, high fecundity and potential for fast growth combined with limited value for human exploitation point to potentially resilient lifeforms in the Anthropocene. However, confirming this is challenging, as several basic life history traits of the Molidae are not yet fully understood. Furthermore, a complicated taxonomic legacy in Mola has caused widespread confusion between species and their distributions, complicating conservation assessments. This presentation reviews potential anthropogenic pressures on the Molidae with a particular focus on fisheries interactions and climate change, and discusses the challenges and potentials of using sunfish bycatch data as proxy for abundance and population trends.

Graeme Hayes | Unresolved Questions About Ocean Sunfishes (Molidae) - A Family Comprising Some of the World’s aLrgest Bony Fish

Based on the findings of leading experts in their respective fields, some of the key unresolved questions for the ocean sunfishes, family Molidae, were compiled. Most of these questions concern the ecology of wild ocean sunfishes. These questions include (i) the number of species in each genus; (ii) the extent of movements along coasts, in the open ocean and at depth; (iii) the spatial, temporal and environmental conditions surrounding spawning and spawning grounds; (iv) variation in diet across individuals, sizes and habitats and lastly; (v) the genetic population structure and overall population status and trends of all species. Major, but ill-defined, anthropogenic threats to the group include bycatch in fisheries, impacts of climate change (e.g., ocean warming and acidification), and elemental and plastic pollution. While the considerable progress made has helped unravel many mysteries of the ocean sunfishes, collaborative research is needed to address these remaining gaps and ensure populations across the world ocean can continue to thrive into the future.

Tierney Thys | Ocean Sunfishes and Society

This talk traces human interest in the ocean sunfishes, Molidae, and their multifaceted uses: from being ichthyological oddities noted by the ancient Greeks, to being culinary delicacies, medical cures, aphrodisiacs, public engagement superstars,  a muse for  artists and video gamers, and a bucket list item for ecotourists. Since the first description of the family Molidae, more than five centuries ago, interest in molids has steadily risen. Alongside a growing understanding of connectivity and resilience within marine systems, these remarkable fish may be most impactful as engaging ambassadors inspiring humanity to care more deeply about the future of the ocean and strive to better safeguard its declining health.