About the kelp and those pesky urchins...

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Posted by seahunt on January 03, 2021 at 07:25:01:


If you have been paying attention there has been an ecological disaster focused on the CA North
Coast. Research shows that since "Starfish Wasting Syndrome" showed up again a few years ago,
because it mostly wiped out the urchin predators, the purple urchin population has exploded.
This has wiped out the North Coast kelp, replacing it with "urchin barrens" that are just bare
rock and zillions of urchins. Current research shows pretty much no Picnopodia Sun Stars,
the primary predator of urchins, from Mexico to British Columbia.
I was sent to a pretty good YouTube video about a Josh Smith's research done while working
for his doctorate at UCSC. He mostly studied the area around Lovers Point in Monterey. He
found some interesting stuff. Here are a few comments but the video is well worth watching.
There can be kelp forests next to urchin barrens.
Urchins exist in two modes, Passive and Active.
Passive urchins are what we would consider fairly normal, hiding in cracks and eating kelp
that falls on them. They have healthy marketable gonads.
When the kelp stipes are at less than 1 per meter, the urchins go into Active roving behavior
and scrape the rocks clean of all algae. They appear almost completely empty on the inside
with no gonads.
Normal predators are Starfish, Rock Crabs, Wolf Eels (rare), Otters.
Otter population has been spiking some in recent years. Urchin consumption has increased
but they do not hunt urchins in the barrens.
Otters are helping to maintain the existing kelp forests...
... Means that if the urchins in the barrens die due to storm or disease, there is kelp
nearby to re-colonize.

Early signs of kelp forest recovery that were seen:
(@36:00) Pt. Pinos... kelp recovered in some deeper urchin barren areas but it was Bull
Kelp instead of Giant Kelp (Macrocystis). It seems that the urchins moved shallower.
Macrocystis seems to be appearing and may start replacing the Bull Kelp.

It was interesintg. He was very cautious about offering opinions but the Q&A made some
points including that Rock Crab are effective predators of urchins and do eat the "active"

One thing I might comment on, California divers should voluntarily just quit taking
Sheepshead fish to allow them to act as predators replacing the missing starfish. It
might prevent some future damage.
I can't believe that the CA F&W still doesn't allow divers to just crush urchins in
place. That is one of the worst of many poor decisions I've seen them make over the years.

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