Ocean Sunfish Research Articles

Species re-identification based on photographs of Ocean sunfishes (Family Molidae) from Philippine waters, including reconfirmation of Mola alexandrini

Detailed biological information (e.g. distribution, size, sex) on ocean sunfishes/molids (Molidae) in Philippine waters is lacking. Four species of ocean sunfishes from Philippine waters are known to date: Mola mola (Linnaeus, 1758), Mola alexandrini (Ranzani, 1839), Masturus lanceolatus (Liénard, 1840), and Ranzania laevis (Pennant, 1776). However, in recent years, the taxonomy of Molidae (especially the genus Mola) has progressed at the global level, and it becomes necessary to review species that occur in Philippine waters. In this study, photographs of Molidae from Philippine waters were collected and morphological research involving museum specimens was conducted. The results of species re-identification based on the photographs of 12 specimens of Molidae obtained in this study were as follows: a specimen of M. alexandrini, five specimens of M. mola, and six specimens of Ma. lanceolatus. Although a specimen identified as M. alexandrini in a previous study was here re-identified as M. mola, the occurrence of M. alexandrini in Philippine waters was nevertheless confirmed in this study on the basis of another specimen. Mola alexandrini and Ma. lanceolatus were confused with M. mola locally, suggesting the importance of preserving real specimens, photographs and genetic samples.

A review of giants: Examining the species identities of the world's heaviest extant bony fishes (ocean sunfishes, family Molidae).

The world's heaviest extant bony fish has long been considered the ocean sunfish Mola mola (family Molidae). However, recent taxonomic research suggests the world record specimen (2300 kg) was actually a misidentified giant sunfish M. alexandrini. Moreover, the history of taxonomic confusion in the genus Mola, combined with anecdotal size information perpetuated in both media and literature, has resulted in uncertainty in regard to species identity and actual weights of very large Mola specimens. In this study, we searched for records of molid specimens with reported body mass over 2000 kg, with a focus on the north-west and south-west Pacific. For each specimen, we reviewed the species identification and assessed the reliability of the information, including if the specimen had actually been weighed. Of the 15 specimens uncovered, we identified one M. mola and 14 M. alexandrini, and found that only five had actually been weighed (one with the viscera removed). Furthermore, we collected length-weight data for verified M. alexandrini specimens from the literature and museum specimens, and established the first length-weight relationship for this species [body mass (kg)=1.1 × 10-5 × total length (cm)3.3248 (29-330 cm total length, n=20)]. These findings are discussed in the context of other extant bony fish species, which allegedly also exceed 2000 kg in body mass, i.e., other Molidae species and the beluga sturgeon Huso huso. Overall, we conclude that M. alexandrini is the only extant bony fish species we could confirm that exceeds 2000 kg, and that basic biological information is generally not collected when very large molid specimens occasionally are stranded or are caught. Finally, we confirm that the world's heaviest extant bony fish specimen actually weighed was a female M. alexandrini (2300 kg, 272 cm total length) captured from Kamogawa, Chiba Prefecture, Japan, on August 16, 1996.

The Ocean Sunfishes: Evolution, Biology, and ConservationThierney M.Thys, Graeme C.Hays, and Jonathan D. R.Houghton, editors. CRC Press, Boca Raton, Florida, 2021. 296 pages. US$190.00 (Hardcover) $50.10 (eBook)

-

Evidence of a range expansion in sunfish from 47 years of coastal sightings

Almost nothing is known about the historical abundance of the ocean sunfish. Yet as an ecologically and functionally important taxa, understanding changes in abundance may be a useful indicator of how our seas are responding to anthropogenic changes including overfishing and climate change. Within this context, sightings from a coastal bird observatory (51.26^circ N, 9.30^circ W) over a 47 year period (from April to October 1971–2017) provided the first long-term index of sunfish abundance. Using a general linear mixed effect model with a hurdle to deal with imperfect detectability and to model trends, a higher probability of detecting sunfish was found in the 1990s and 2000s. Continuous Plankton Recorder (CPR) phytoplankton color indices and the annual mean position of the 13 ^{circ }C sea surface isotherm were significantly correlated with the probability of detecting sunfish. An increase in siphonophore abundance (as measured by the CPR) was also documented. However, this increase occurred 10–15 years after the sunfish increase and was not significantly correlated with sunfish abundance. Our results suggest that the observed increase in sunfish sightings is evidence of a range expansion because it was significantly correlated with the mean position of the 13 ^{circ }C isotherm which moved northwards by over 200 km. Furthermore, the observed increase in sunfish occured 10 years before sunfish sightings are documented in Icelandic and Norwegian waters, and was concurrent with well-known range expansions for other fish species during the 1990s. This study demonstrates how sustained citizen science projects can provide unique insights on the historical abundance of this enigmatic species.

First Report on the Elemental Composition of the Largest Bony Fishes in the World, the Ocean Sunfish (Mola mola) from the Mediterranean Sea

In this study, element levels (Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, V, As, Ba, Sr, K, Pb) in the liver, gill, muscle, and stomach tissues of Ocean Sunfish (Mola mola) caught from Mersin Bay in 2018 were determined, and the first report on the elemental composition of M. mola from the Mediterranean sea presented. Spectrophotometric methods were used in the determination of tissue element levels. Metal analysis of the tissues was performed on the ICP-MS device. The reference material IAEA-436 was used to follow the quality of the analytical process. Metal accumulation in M. mola tissues was determined as K> Fe> Zn>Sr> Cu> As> Al> V>Mn> Ni> Ba> Cr>Pb> Co. A statistical difference was found between tissues in terms of metal levels. It was determined that Fe and Cu were higher in the liver, Mn, Zn, Sr in gill, Al, Pb, Cr in muscle tissue. There were no statistical differences between the levels of As, V, and Ba detected in gill and muscle tissues. The K levels were similar in all tissues except the liver.

Influence of the 2014–2016 marine heatwave on seasonal zooplankton community structure and abundance in the lower Cook Inlet, Alaska

During the 2014–2016 Pacific marine heatwave (MHW), seabird die-offs, declines in forage fish populations, and the appearance of subtropical marine taxa (e.g. ocean sunfish, skipjack tuna) occurred in the northern Gulf of Alaska; however, the response of the zooplankton community to the MHW remains poorly understood. As part of the Gulf Watch Alaska program in Cook Inlet, zooplankton, phytoplankton, and a suite of oceanographic variables were collected monthly from 2012 to 2018. Surface zooplankton were collected via vertical tows (0–50 m) with a 333 μm bongo net along with CTD data and chlorophyll a concentration. Generalized additive models showed that seasonal zooplankton abundance peaked mid-June and declined into late January. During the MHW, monthly temperature anomalies ranged from +0.2 to +2.8 °C in 2015 and 2016, but monthly means of large lipid-rich calanoid copepods showed no clear declines in abundance compared to before and after the MHW suggesting that these copepods had some resiliency. An indicator species analysis using 88 of the most common zooplankton taxa produced five groups of zooplankton based on season. A BIO-ENV Best model showed that the environmental variables best explaining the observed zooplankton community structure included SST, temperature of the top 50 m of the water column, mixed layer depth (MLD), MLD temperature, and integrated chl a (ρ = 0.3491, Mantel Test: r = 0.3491, α < 0.05). Seasonal transitions of community groups displayed a phenological shift in 2016 when the late spring group of meroplanktonic larvae and the fall group of warm water copepods (WWC) typical of the Northern California Current system appeared earlier and persisted for longer compared to before and after the MHW. WWC abundance increased during the fall seasons of the MHW. Throughout 2015–2016, the elevated abundance of WWC compared to previous years and before/after the MHW suggested that warmer than average oceanographic conditions in the winter of 2015/2016 may have been sufficient to allow for an overwintering population in this area. A potential overwintering population of a warm water predatory copepod, Corycaeus anglicus, was observed and may have direct fine scale predator/prey impacts on zooplankton in this region.

Thermoregulation of ocean sunfish in a warmer sea suggests their ability to prevent heat loss in deep, cold foraging grounds

During behavioural thermoregulation, it has been demonstrated that fish alter their heat exchange rates between warming and cooling. In the case of the ocean sunfish (Mola mola), there is a several-fold difference in the rate of heat exchange between foraging in the deep, cooler water and recovering body temperature at the warmer surface. Increased heat gain during warming has been suggested, but there is also the possibility of preventing heat loss during cooling. To examine this, we measured the vertical movement and muscle temperature of three captive sunfish that were released into the field under warmer conditions and compared them with previously reported sunfish that foraged in cooler deep water. The released sunfish vertically moved from near the surface, where the water temperature was 21–25 °C, to depths of 150–200 m, where the water temperature was 15–17 °C. All sunfish occasionally appeared on the sea surface and sometimes remained at the surface for <41 min. However, they reduced their muscle temperature by diving before their muscle temperature exceeded 21–22 °C, suggesting behavioural thermoregulation using the cooler water temperature at depth. In addition, the feeding events detected by video were limited to depths shallower than 60 m. This is in contrast from previously observed sunfish behaviour, in which fish were reported as recovering their body temperature using warmer temperatures at the surface after foraging in deep, cooler water. The heat-budget models indicated that the whole-body heat-transfer coefficients during warming in this study were similar to those of previously reported sunfish that had recovered their body temperature at the sea surface after foraging in deep, cooler water. In contrast, the heat-transfer coefficients at cooling in this study were higher than those of sunfish foraging in deep, cooler water. This suggests that ocean sunfish may have the ability to prevent heat loss in the physiological regulation of heat exchange rate during thermoregulation, while also indicating that sunfish have the ability to respond to changes in the temperature environment by altering their behaviour and heat exchange rate.

Behavioural thermoregulation linked to foraging in blue sharks.

Large pelagic fishes often dive and surface repeatedly as if they were airbreathers, raising a question about the functions of these movements. Some species (e.g., bigeye tuna, ocean sunfish) apparently alternate foraging in deep cold waters and rewarming in shallow warm waters. However, it is unclear how prevalent this pattern is among species. Blue sharks are the widest-ranging pelagic shark with expanded vertical niches, providing a model for studying foraging–thermoregulation associations. We used electronic tags, including video cameras, to record the diving behaviour, muscle temperature, and foraging events of two blue sharks. During repeated deep dives (max. 422 m), muscle temperature changed more slowly than ambient water temperature. Sharks shifted between descents and ascents before muscle temperature reached ambient temperature, leading to a narrower range (8 °C) of muscle temperature than ambient temperature (20 °C). 2.5-h video footage showed a shark catching a squid, during which a burst swimming event was recorded. Similar swimming events, detected from the entire tag data (20 − 22 h), occurred over a wide depth range (5 − 293 m). We conclude that, instead of alternating foraging and rewarming, blue sharks at our study site forage and thermoregulate continuously in the water column. Furthermore, our comparative analyses showed that the heat exchange rates of blue sharks during the warming and cooling process were not exceptional among fishes for their body size. Thus, behavioural thermoregulation linked to foraging, rather than enhanced abilities to control heat exchange rates, is likely key to the expanded thermal niches of this ectothermic species.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00227-021-03971-3.

On the presence of an ocean sunfish (Tetraodontiformes, Molidae) in the Miocene Pietra Leccese formation of Southern Italy

On the presence of an ocean sunfish (Tetraodontiformes, Molidae) in the Miocene Pietra Leccese formation of Southern Italy

Tetraodontiformes (Osteichthyes, Actinopterygii) from the Miocene of Argentina: with the southernmost record of fossil Tetraodontidae

Teleostean evolution produced enormous variation in tooth morphology. This variation is related to the exploration and exploitation of very diverse dietary niches. Among extant fishes, several taxa of the order Tetraodontiformes (e.g. pufferfishes, porcupinefishes and ocean sunfishes) have evolved highly specialized beak-like tooth structures. Here we provide the first description of tetraodontiform crushing beaks from Argentina. A single complete premaxillary beak recovered from the early Miocene Gaiman Formation in Chubut Province is assigned to Molidae based on its premaxillaries being completely fused to one another along the midline, general morphology, and size. Moreover, due to the putative presence of rows of teeth fused to the thick and massive bone structure, the specimen might belong to the genus Ranzania Nardo, 1840. Several premaxillary beaks recovered in the late Miocene Paraná Formation of Entre Ríos Province are assigned to Tetraodontidae Bonaparte, 1832 based on the presence of long, slender, rod-like, and parallel dental units; premaxillae not fused in the midline but articulated by interlocking emarginations, and a few small and one large trituration dental units. Argentinian tetraodontiform fishes inhabited the warm-temperate Paranense and Patagoniense Seas (marine transgressions developed in southeastern South America) during the early-late Miocene; these specimens are the southernmost fossil record of the group worldwide. Tetraodontiforms are extremely rare in recent Argentinian marine waters. The new fossil records agree with the higher sea water surface temperatures suggested both locally and worldwide for the Miocene.

Evolutionary Dynamics of the OR Gene Repertoire in Teleost Fishes: Evidence of an Association with Changes in Olfactory Epithelium Shape.

Teleost fishes perceive their environment through a range of sensory modalities, among which olfaction often plays an important role. Richness of the olfactory repertoire depends on the diversity of receptors coded by homologous genes classified into four families: OR, TAAR, VR1, and VR2. Herein, we focus on the OR gene repertoire. While independent large contractions of the OR gene repertoire associated with ecological transitions have been found in mammals, little is known about the diversity of the OR gene repertoire and its evolution in teleost fishes, a group that includes more than 34,000 living species. We analyzed genomes of 163 species representing diversity in this large group. We found a large range of variation in the number of functional OR genes, from 15 in the Broad-nose Pipefish Syngnathus typhle and the Ocean Sunfish Mola mola, to 429 in the Zig-zag Eel Mastacembelus armatus. The number of OR genes was higher in species when a multilamellar olfactory rosette was present. Moreover, the number of lamellae was correlated with the richness of the OR gene repertoire. While a slow and balanced birth-and-death process generally drives the evolution of the OR gene repertoire, we inferred several episodes of high rates of gene loss, sometimes followed by large gains in the number of OR genes. These gains coincide with morphological changes of the olfactory organ and suggest a strong functional association between changes in the morphology and the evolution of the OR gene repertoire.

A foraging ocean sunfish and the ‘nearest neighbor’ problem

A predator that preys on randomly-distributed stationary energetically-equivalent small prey will probably choose its next prey to be the nearest one. But what if no prey is found within the detection range of the predator? It is hypothesized that in this case the predator will move along an arbitrary chosen direction until a prey is detected, and turn towards it. In a stochastic environment this strategy leads to a certain distribution function of distances that the predator moves between consequent prey catches. It is shown that when the detection range of the predator exceeds the average distance between prey, this distribution function becomes the nearest neighbor distribution function, whereas; wherew when the detection range is small as compared with the average distance between prey, it becomes the exponential distribution, as the distribution of distances between neighbors on a line. In the first case, the average distance between catches becomes roughly half the average distance between prey; in the second case, it becomes inversely proportional to the square of the detection range. Ocean sunfish preys on practically stationary jellyfish at depth of more than a hundred meters, in dim light. Plausibly, it can detect jellyfish only at close quarters, and hence its detection range is probably small as compared with the average distance between prey. Analysis of the tracking data from seven animals over a few days yielded many thousands of swimming segments separating consequent prey catches. Indeed, lengths of these segments were shown to have the exponential distribution. This finding not only supports the initial hypothesis of this study, but also reveals the fragility of the energetic balance of this animal. A two-fold decrease in the detection range (e.g. due to a decreased visibility) is expected to increase the average distance it moves between catches four-fold, and hence decrease its specific energy intake (the number of jellyfishes per distance moved) by the same rate.

First video evidence of urination by a captive ocean sunfish, Mola mola

First video evidence of urination by a captive ocean sunfish, <i>Mola mola</i>

Catch data for ocean sunfishes (family Molidae) by set nets in 12 prefectures, Japan, from 2000 to 2020

Catch data for ocean sunfishes (family Molidae) by set nets in 12 prefectures, Japan, from 2000 to 2020

Tissue and gender-related differences in the elemental composition of juvenile ocean sunfish (Mola spp.)

Trace elements are potentially critical contaminants of aquatic environments and fish, occupying upper trophic levels, are especially vulnerable to bioaccumulation. Due to public health concerns, however, data on the elemental composition of non-commercially important marine species are particularly lacking. Ocean sunfish (Mola spp.) attain a low commercial value worldwide and information on their elemental composition is limited. In this context, we examined the concentration of 11 trace elements (V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Cd and Pb) in eight tissues [brain, gills, gelatin (subcutaneous white gelatinous layer), gonads, spleen, liver, white muscle and red muscle] of 20 juvenile specimens (37.5–85.5 cm TL). Gender-related differences were solely found in the gonads and chiefly for essential elements possibly as a result of their importance in embryo development. Overall, Zn and As were the elements observed in greatest concentrations in body tissues. The considerably high presence of As should be related to the dietary preferences of juvenile ocean sunfish. Considerable inter-individual variability in the concentration of each element in any given tissue was observed, especially in the liver, likely originating from the inclusion of both benthic and pelagic prey in the diet of analysed fish. Greatest elemental loads were found in the liver and gills whereas lowest loads were observed in white muscle, brain and gelatin. Moreover, a clear distinction in elemental load and elemental composition was observed between white and red muscles, likely deriving from existing divergent metabolism-related physiological adaptations linked to their different roles in locomotion.

Confirmed Occurrence of Mola mola (Linnaeus, 1758) from Mersin Bay (Northeastern Mediterranean)

In June 2018, a single female specimen of the Ocean sunfish, Mola mola (Linnaeus, 1758) (122 cm in total length and 80 kg in weight) was caught by a commercial trammel net at a depth of 393 m in Mersin Bay (Bozyazi coast), Turkey. This paper presents the first substantiated occurrence and hence, the confirmation of M. mola in the Northeastern Mediterranean, Turkey. Morphological and meristic measurements of the specimen were made and recorded with the catalog number MEUFC-18-11-101 in the Museum of the Systematic in, Mersin University’s Faculty of Fisheries. Morphometric and meristic data matched other recordings of this species from parts of the Mediterranean, and the historical captured record of the species in the Mediterranean was documented.

On the Ocean Sunfishes (Mola mola, Linnaeus 1758) By-Caught Off the Mediterranean Coast of the Gaza Strip, Palestine

The Ocean Sunfish or Common Sunfish or Common Mola (Mola mola, Linnaeus 1758) belongs to the Molidae family...

Bulk tissue and amino acid stable isotope analyses reveal global ontogenetic patterns in ocean sunfish trophic ecology and habitat use

Bulk tissue and amino acid stable isotope analyses reveal global ontogenetic patterns in ocean sunfish trophic ecology and habitat use

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 85000+ longline sets spanning 24 yr, &gt;50° in longitude, and &gt;45° 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.

Mola asinaria and mola jumentaria, or the representations of "Pompeii" type grain millstones on imperial lamps.

Mola asinaria and mola jumentaria, or the representations of "Pompeii" type grain millstones on imperial lamps.