Yes but I believe they marketed the people as Soylent Green if I’m not mistaken.
Sharks?
I think the rats were probably uninvited, like they are on most ships. And they may have tried to bring pigs, but they didn’t survive the voyage (or became emergency rations). Rats and dogs don’t require as much food as pigs.
That’s the rational explanation. Although it’s surprising that on their small boats a pair of rats went unnoticed. Perhaps they floated there somehow, don’t know if that’s realistic for the location.
ETA: Well I guess just one pregnant rat was all that was needed.
I know, it was whoosh on my part too. 
Why not? Rodents are considered good eating in lots of cultures. I’ve eaten rabbit (technically not a rodent, but close), squirrel, muskrat, guinea pig, and paca. I’ve also eaten Polynesian rats when some colleagues in New Zealand who were doing a study on them decided to fricassee some of the ones they had trapped. (This totally freaked out a journalist who was with our group. More for the rest of us.)
Guinea pig and paca are excellent, rather like pork. I can report that rat, on the other hand, tastes very much like rat.
Rats were considered a delicacy by the Maori. In fact, after the arrival of Europeans they preferred the introduced Norway rats because these were bigger and meatier than the Polynesian variety.
Polynesian canoes, especially those used for colonization, could be very large. It wouldn’t be hard for a rat or two to remain concealed at the bottom of a pile of food sacks stacked on board for the voyage.
Certainly possible. The other aspect of this is that we don’t know why they went there. They could have been searching for new islands or they could have been washed there by a storm. They might have been there before they settled and returned figuring on surviving just on the moa population. Or maybe they intentionally brought rats to eat. If there’s anything at all to eat then rats will survive and multiply.
<somewhat off-topic>
This seems like quite a stretch, based on biological/evolutionary concepts.
Poisonous (as venomous) species are sort-of incompetent ones – they develop venom because they can’t compete otherwise. Apex predators don’t. (The lion doesn’t need anything more than his teeth & claws to be king of the jungle. And grizzly bears don’t need poisonous claws to rule the northern forests.) So the idea of such a species “out-competing all other fish species” is rather unlikely.
Poisonous (as in dangerous to eat) species develop poison/bad taste that is targeted to the species that prey on them. The evolutionary advantage would come from being poisonous to bigger fish & to sharks. No point to poisoning humans, when you are an invasive species first encountering them. (That might develop after decades of fishing, where the bad-tasting fish get tossed back, and the good-tasting ones are eaten by the fishermen.) There could be a random coincidence that causes a poison aimed at deterring shark feeding to also make humans sick – but your story ought to show this as an unlikely coincidence that just happened to occur.
Also, this ignores the tendency of humans to take actions to protect their edible food sources. For exaple, a lot of effort has gone into eradicating the sea lamprey, which invaded the Great Lakes and preys on the lake trout. Or the efforts of local fishing groups to combat the Asian carp that are moving up the Mississippi river.
In your example, the natives would have caught “nets full of the poisonous fish” and dumped them onshore (fertilizer for their fields), to help preserve the edible native fish.
On the other hand, cane toads are a real example that would fit leahcim’s criteria. It’s not impossible.
There are islands that don’t receive much rain, right? Lack of water could then be a story point.
I was actually thinking of the lionfish, which is an invasive species with venomous spines which is in the habit of overrunning reefs and out-competing the native life. As it happens, once you cut off the spines, lionfish is delicious, but I could imagine a more spiney, less meaty version.
[QUOTE=t-bonham@scc.net]
This seems like quite a stretch, based on biological/evolutionary concepts.
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But the invasive species would not have evolved in this ecosystem at all. In its home habitat, the species could be a bottom-of-the-food chain scrub that needs to be poisonous and venomous and to reproduce like crazy just to maintain population. A fish like that getting transported to this island, finding it has no local predators, and taking over doesn’t seem like much of a stretch.
A lot of effort has been put into these initiatives specifically because people have seen what happens when invasive species come in and they fail at controlling them. That level of effort may be beyond the capability of the islanders, especially if the invaded region is much larger than just their fishing areas.
Robot Sea Monsters created by Evil Geniuses For A Better Tomorrow and controlled by the International Communist Conspiracy keep killing all the fish/fishermen.
Are you having a competition with Mangetout ? 
I was thinking lionfish, too. There’s a nice short article here, with links to more research. Here’s another.
From a story pov, the invasive fish could have came in, destroyed the local fish population, and then skipped town, leaving little behind.
When we were in Bali (and also mentioned in many of the guidebooks about Bali), several of the local people mentioned how crazy tourists are for going far into the water. It’s not really their thing. There are some boats, but most of them take tourists out to look for dolphins and the such. There’s apparently not a big traditional fishing industry, because the Balinese think the ocean is insanely dangerous. Given their propensity for monsoons and sharp coral reefs, it’s not really a stretch, but it seems there’s religious basis for their fears, as well.
So I could believe a group of people might develop an even stronger taboo against the ocean, and fishing, with the right backstory. Maybe their ancestors were fleeing Something Bad and decided that their children should be dissuaded from ever leaving the island. Maybe some early ruler nearly drowned and water became unfashionable. People are weird, and taboos can be very strong.
How many kinds of rodents has he eaten?
Invasive fish species don’t tend to come in, take over, and leave town never to be heard from again… they usually stick around in small (or large) numbers keeping the native species either constantly under threat or simply wipe them out and take over the ecosystem remaining there until something more competitive arrives.
Lion fish wouldn’t really work for this hypothetical story as their spread seems connected to the aquarium industry. I don’t think there was a lot of trans-oceanic aquarium fish shipping and flushing back in the 40’s or earlier…
Many fish that inhabit coral reefs are poisonous (ciguatera toxin). And, as was mentioned, crystal-clear water are pretty sparse anyway. What puzzles me is where (due to religious or social taboos) eating fish is prohibited-when there was a famine in Eritrea, a japanese aid worker noticed that the local waters teemed with oysters, clams, and crabs-all good, high protein foods. The locals would not eat them because they were “unclean”.
Plus, lionfish are a food source themselves, once you know to cut off the spines.
But something similar that has poisonous flesh, and maybe arrived in bilgewater of cargo ships rather than aquarium cast-offs would do the trick.