Hello and welcome to Part 2 of the special edition Myth Buster’s Blog!! Following the fishy facts touted by sunfish-loathing Scout Burns that went viral last week, I have been exploring the incredible ecology of the ocean sunfish and answering a lot of fake news claims! So buckle up and get ready for a whistle-stop tour of fascinating (and scientifically verified!) fish facts.
My favourite issue that Scout has with sunfish is that despite being “so huge” they are not even “decent predators” …unless you are a prey item of course! The key biological definition of a predator is ‘an animal that naturally preys on others’ and so sunfish are actually classed as oceanic predators!
With jaws not-so-dangerous to people, the sunfish (or Mola) is a voracious predator of gelatinous prey!
If we consider a “decent predator” as one which is harmful to humans, then as Scout mentioned, sunfish can be dangerous due to their incredible size and are alleged to have caused a death already by breaching and hitting a person. But as a biologist, this doesn’t seem like the best method for classifying predators…(although it should qualify as entry to the Darwin Awards!)
Back to sunfish prey items, (an area quite a few researchers have been working on over the last 5-10 years,) Scout states “They mostly only eat jellyfish because [it has] a possibility of drifting into their mouths I guess. Everything they do eat has almost zero nutritional value and because it’s so stupidly fucking big, it has to eat a ton of the almost no nutritional value stuff to stay alive. Dumb.” Again, this statement needs a bit of work to reach the underlying truth… Yes sunfish mostly eat jellies, but for smaller sunfish (<1 m), up to 40% of their diet is actually made up of seafloor creatures including crustaceans, molluscs and even some fish species. I even wrote a blog post about this 3 years back…
So many choices….
To find jelly prey in the open ocean, not just jellyfish medusae but also other gelatinous creatures such as siphonophores, ctenophores and pyrosomes (see photos!), is a tough job. Sunfish constantly patrol the world’s oceans searching for prey, travelling long distances both horizontally and vertically to find their food. When they locate prey items, such as a jellyfish, they know to only eat the most energetically nutritious parts, the gonads and oral arms (yum!) before leaving the rest as not worth bothering digesting. It’s an incredible strategy that not many creatures are physically able to exploit and something that we are still trying to understand and explain.
Sunfish prey items clockwise from top left: Ctenophore – (Bolinopsis infundibulum), Siphonophore (Marrus orthocanna) and Pyrosome (unknown species)
Photo credit www.photolib.noaa.gov, en.wikipedia.org/wiki, carnivoraforum.com
Scout then moves on from thinking of sunfish prey, to thinking of sunfish as prey: “They do sometimes get eaten though. But hardly. No animal truly uses them as a food source.” Again, this is a little misguided. Although larger sunfish are less predated on (but have still been found inside large sharks, sealions, orca etc.) the sunfish start out life in the plankton as tiny eggs less than 1 mm across. This puts them on the menu for almost every creature in the sea! As they grow, the number of predators able to cope with such a large item decreases, but they are still removed from the world’s oceans in their hundreds of thousands by… you’ve guessed it: us! There are huge markets for ocean sunfish meat across the Far East (Taiwan and Japan in particular) and they are also captured as unwanted bycatch by fisheries across the world. It is these enormous catch figures that have led to the ocean sunfish being classified as Vulnerable to extinction by the IUCN Red List.
Fisheries capture of ocean sunfish and a dish made of sunfish
(Photo credit; Lukas Kubicek and commons.wikimedia.org)
Scout reckons their survival strategy is dependent on the sunfishes extreme fecundity, “it would be statistically improbable, dare I say impossible that there wouldn’t be at least one… left surviving at the end of the day”. The sunfishes incredible fecundity has been estimated from one study that suggested a single female could contain up to 300 million eggs, (although it is highly unlikely that a sunfish would release all their eggs at once!) This number is brandished a lot in ocean sunfish ecology, but we need to remember this figure was estimated from one fish; it does not represent the average number of eggs per sunfish and has not been examined further since the original study in 1921…
The statistically probability of larvae survival is harder to predict… in cases of extreme fecundity (known as being an r-strategist) an animal must produce lots and lots of offspring because the overall odds of survival are minuscule. We don’t currently know how many sunfish there are in the seas, but it appears that not many of these offspring survive otherwise evolutionary speaking, it would be an unnecessary waste of resources and not selected for.
A simple outline of species reproductive strategies:
- “K strategists” which have fewer offspring with higher energy input and high parental care which are more likely to survive (e.g. polar bear)
- “r strategists” which have high abundance of offspring, with low energy input and little to no parental care which have a poor chance of survival (e.g. ocean sunfish)
Of course this rant does not, in my opinion constitute as “proof that God has abandoned us.” But unfortunately Scout feels so strongly to “hate the f*** out of this complete failure of evolution… if I ever see one, I will throw rocks at it.” As much I as love to introduce people to the incredible species I work on, considering that we currently believe these fish are Vulnerable to extinction and seem to have an important role in ecosystem functioning, (and animal cruelty is frowned upon), perhaps it’s best that these two never meet.
If however, anyone ever has any questions on ocean sunfish or wants to know more details about their fascinating ecology please head to my twitter page @SunfishResearch or visit my blog firstname.lastname@example.org