Is smashing urchin in the ocean good for population control?
Posted by DePlano@reddit | marinebiology | View on Reddit | 15 comments
Sorry if this is a common question
I live where the purple urchin population is disproportionate to what it should be.
I have read that divers smash them to control their numbers, but I have also read it releases sperm, which can increase the population
I try and process them out of the ocean, but I don't know if it matters.
If I am diving is it better to smash or not?
Aqua_Splendor@reddit
The population of urchin is tied with algae availability, why would want more algae?
Is there another reason for smashing?
DePlano@reddit (OP)
There is a disproportionate amount of purple urchin and they are bad for kelp beds, which other animals depend on.
Someone else who I assume know mores more than me gave better opinions than me on good solutions to the problem
sphks@reddit
I have seen the evolution of sea urchin population in my area for about 10 years. That's insteresting.
First, sea urchin are munching on algae on rocks. Some big rocks became clean (nothing on it but sea urchins).
Then, the sea urchin went to another rock and the clean rocks are covered by sabellaria alveloeta after some years. https://en.wikipedia.org/wiki/Sabellaria_alveolata
https://commons.wikimedia.org/wiki/File:Sabellaria_alveolata_reef.jpg#mw-jump-to-license
Then, maybe when the worm dies, the holes are used by small animals and small algae. Shrimps, small fishes, nudii, etc. After something like 10 years, what was a rock with green algaes only, then nothing at all but sea urchins, became a rich ecosystem.
Disclamer : I am not a Marine scientist. I have not done a scientific survey. I just use to freedive on the same spot for 40 years.
Not-Now-John@reddit
A beneficial species in one ecosystem could be a problem in another. OP seems to be describing kelp forests, which are made from kelp. Over abundance of urchins means no kelp which by definition means no kelp forest.
deleted_by_reddit@reddit
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marinebiology-ModTeam@reddit
Your post was removed as it violated rule #8: Responses to identification requests or questions must be an honest attempt at answering. This includes blatant misidentifications and overly-general/unhelpful identifications or answers.
deleted_by_reddit@reddit
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marinebiology-ModTeam@reddit
Your post was removed as it violated rule #8: Responses to identification requests or questions must be an honest attempt at answering. This includes blatant misidentifications and overly-general/unhelpful identifications or answers.
reverendloc@reddit
Smashing is only legal in one area in California right now. This is controlled by CDFW.
North of the SF Bay you are allowed to keep 40 gallons of purple urchins a day. This is a lot of urchins. You must have a fishing license. You can smash urchins and it counts against your 40 gallons if you are using them as bait in the act of fishing.
If you’d like to cull purple urchins by smashing you need to be in Caspar cove in Mendocino County. There are non-profits that organize weekends with air compressors on site, although the events are done for the 2025 season. Culling efforts are reported using a Google form and divers culling must have a fishing license.
My understanding is that research into whether culling triggers spawning events has not shown a correlation.
If you have any questions about culling efforts on the North Coast feel free to DM me.
DePlano@reddit (OP)
Awesome, thank you!
exclaim_bot@reddit
You're welcome!
Hizzeroo@reddit
Smashing them doesn’t lead to population increase because of “released sperm”. Maybe if you did it when every other urchin was actively in the process of spawning it would, but otherwise no. Doesn’t do harm but it’s futile as a long-term control mechanism, because of the sheer number of urchins.
What would be more effective would be restoring keystone species that control urchins, on the West Coast that would be sea otters. Where sea otters are reestablished, they control the urchin population which intern leads to recovery of kelp forests.
So go ahead and continue to smash them (or even better, bring a bag with you and collect them to eat). Just be sure you’re doing it within the laws of wherever you live, in California that would restrict the activity to certain areas and requires a fishing license.
tony-thot@reddit
A larger effect has been seen with the depopulation of sunflower stars due to sea star wasting disease, about 90-95% of their population has been lost in recent years. Sea otters definitely eat purple sea urchins as well and regulate the population. That said, they (and maybe this applies to their other predators) largely ignore urchins barrens as those urchins are not very nutritious so I think the most effective approach would be active removal of individuals in barrens while restoring keystone species.
Hizzeroo@reddit
Yes, SSWD is a disaster. Purple urchins are affected as well but it’s decimating sea stars much more quickly.
DePlano@reddit (OP)
Awesome, thank you. Now I need to correct some misinformation I apparently was spreading