Nudibranchs can be found in saltwater along nearly every coast line in the world. They live in a wide variety of marine habitats – some species live in the intertidal zone while others are strictly pelagic and there are even deep sea species. A few nudibranch species can be truly large, but the vast majority are small and some are so tiny you’re likely to overlook them unless you’re specifically searching for them. To further complicate matters, some nudibranchs are nocturnal, some bury themselves under sand when the tide goes out and some are very cryptic making good use of camouflage to match their food source. Then there’s seasonality to consider. Although seasonality has been poorly studied, many nudibranchs are abundant during different times of the year and a single location might vary dramatically from one month to the next. The good news is, many nudibranchs are brightly and even flamboyantly colored so they can really stick out in the tidepools and on the seaweed.
Finding nudibranchs isn’t always easy, but with practice and a little knowledge you can be successful.
CHOOSE A LOCATION
Are you a casual tidepooler? Diver? Hardcore nudibranch explorer? Whatever you are, the first decision to make is where you’re going to search for nudibranchs.
AT THE BEACH
Generally speaking, nudibranchs are more commonly found on rocky beaches, especially those with tidepools. But some species are found on sandy beaches with little in the way of rocks. When looking for nudibranchs on the beach if the tide is out, look first for the pools of water left behind to see if any nudis are crawling around. You’re likely to see them on seaweed, hydroids or other surfaces. If you can’t find any, or if your beach doesn’t have actual tidepools, don’t give up. Nudibranchs often find shelter when they’re left out of water by the tide, so try looking under rocks (just remember to put the rock back exactly how you found it, with the same side down). They will also hide in crevices between rocks, under ledges and in or under seaweed, so don’t hesitate to dig around in the seaweed and get low down to look underneath rocks. Avoid tidepools which are subjected to wave action because it stirs up the sediment making it very hard to see and it can also dislodge the nudibranchs from their hold on seaweed and rocks, blowing them into harder to find regions of the pools.
ON THE DOCKS
You can also look on floating docks for nudibranchs. Simply find a dock, lay down along the edge and look down into the water. Seaweed, barnacles, hydroids, tunicates, sea anemones and much more all settle on the sides of the docks to make a permanent home. Nudibranchs can be found among the biofouling on the docks. The best part is, because the docks float, it doesn’t matter if it’s high tide or low, they’ll always be accessible. However, marinas with a lot of boat traffic can create too much wave action and make it hard to see. In addition, windy days can also kick up excessive wave action and make conditions challenging.
DIVING & SNORKELING
There are some nudibranchs that can only be found by diving and there are copious resources for finding nudibranchs while diving so search online if that’s your choice. Snorkeling is another option.
What do you need to search for nudibranchs? Absolutely nothing but your own eyes. However, there are some things that might make your searching a little easier and more comfortable.
FLASHLIGHT: Nudibranchs like to hide in rock crevices, under rocks and ledges and among seaweed and a powerful flashlight can help reveal them.
GOOD SHOES: Tidepools can be slippery and dangerous, not to mention wet. Keep yourself safe from falling, getting torn up hands from barnacles and keep yourself warm if you live in a cold water region, with good waterproof boots. Insulated boots allow you to walk in the water for long periods. Hip waders let you go deeper into the water without getting wet pants. If it’s warm enough, aquatic sandals with a good gripping sole also work well.
CAMERA: Nudibranchs are incredibly photogenic, so you’ll definitely want to document them. Besides the fact they’re fun to photograph, it will help with identification once you’re back home again and consulting books and website and if you want to share your observations and/or get identification help on iNaturalist, you’ll need a photo. If you are serious about nudibranchs, an underwater camera can be really beneficial.
HAND LENS: A hand loupe or magnifying glass can enlarge some of the smaller species for observation and identification.
PLASTIC CONTAINER: Sometimes the location a nudibranch is found is not suitable for observation, so a plastic container filled with sea water can be a handy temporary observation tank to watch the nudibranch or take photos. Just remember to return the nudi exactly back to where you found it, which is likely near their food source, and don’t expose them to the sun in the container for too long.
KNEE PADS: If you search on docks or at tidepools with sharp barnacles, knee pads can protect your pants and knees from the harsh surfaces because you will spend a lot of time kneeling.
HIKING POLE: If you’re not very steady on your feet, have bad knees or just want extra safety, you can carry a hiking pole to help balance yourself in tidepools and when walking over seaweed.
FIRST AID KIT: Because barnacle cuts will happen, so carry a small kit with at least bandages and disinfectant.
For nearly all nudibranchs, it’s worth waiting for the lowest tides of the year before searching for nudibranchs on the beach. Most that live in the intertidal zone, stay fairly low down. The very lowest tides of the year might expose nudibranchs rarely found during only moderate low tides, so study your tide charts in advance and mark the lowest days on your calendar to make plans for nudibranch hunting.
Remember that most nudibranchs are small, so adjust your eyes to search for little organisms. Forget crabs and sea stars, nudibranchs are even smaller and harder to find. And be patient. Don’t simply glance at a tidepool and walk on. Kneel down, settle in and observe. The longer you watch, the more the tidepool will reveal. Nudibranchs move slowly, but they do move and can catch your eye if you’re sharp.
When they’re out of the water, nudibranchs almost completely lose their shape and turn into a blob. Their cerata, gills and rhinophores sag down or they retract them into their body while they’re out of the water. If you find a blobby nudi, sometimes you can gently pull them off whatever they’re clung to and temporarily place them in shallow water to see them well enough to identify or take a photo. Some species and individuals really resist this however, so don’t pull and risk hurting them if they’re not easy to remove. When you’re done, put them back in the exact location you first found them because they may have been in the process of feeding, looking for a mate, or looking for somewhere to lay eggs and we don’t want to disrupt that.
Check the wrack line because some species, like Fiona pinnata who feeds on pelagic barnacles, may wash up on flotsam.
TAKE IT TO THE NEXT LEVEL
STUDY LOCAL SPECIES
For the serious nudibranch searcher, the best thing you can do is to study your local species. There are many field guides for regions around the world and they’re well worth consulting to get familiar with the species which can be found in your area. Some species are hyper local, some are circumglobal and some expand their range during El Nino events.
RESEARCH FOOD SOURCE
Perhaps the single best way to find nudibranchs is to find their food source and while not all species food preferences are yet documented, many are. Field guides frequently note what nudibranch species eat. Prey ranges from bryozoa, hydroids and sponges to anemones and jellyfish. Learning to recognize their prey can help lead you to the nudibranchs themselves. For example, some species feed on sea pens, so if you can find a location where sea pens live, you are more likely to find those nudibranch species.
SEARCH FOR EGG MASSES
Nudibranch eggs often tend to be easier to find than nudibranchs because they’re stationary and often brightly colored in white or yellow or other obvious colors. Studying the eggs of nudibranchs can tell you what nudibranchs live in the area without actually seeing them. Since they’re often seasonal, if the eggs are there but they aren’t, it might be worth checking that location later in the year, or regularly throughout the year, to find them.
REFERENCE SCIENTIFIC NAMES
Nudibranch guide books are outdated before they’re printed because the taxonomy is constantly changing. Fortunately, there is a comprehensive database called WoRMS (World Register of Marine Species) that keeps track of all the old scientific names and links to the most recent, accepted name.
Many people document their nudibranch observations, so if you want to know where a certain species has been found in your region, look it up on iNaturalist to get an idea. Some people have even made nudibranch species lists for certain locations.