Identifying Parablennius Species in Hawaii

According to Wikipedia, Parablennius is a diverse genus of combtooth blennies found in the Atlantic, western Pacific, and Indian Ocean.

iNaturalist is an organization with users worldwide, including both professional naturalists and amateur enthusiasts. Any member can observe species and upload photos for others to identify. This is a valuable tool for documenting plant, animal, and non-animal species in any location. I am new to this app, but it has helped document marine species in Kawaihae Harbor. My focus is on rare, endangered, or threatened species. Non-listed species documented are equally important to showcase the reef’s diversity.

Two considerations come from using the application. First, it could be exploited maliciously by poachers. This is a serious concern for its developers and the community. The most severe impact is on the natural environment. The app also has known biases that can lead to misidentification of similar species. I will write about this only.

I want to share an example of how two fish species—the Tassled Blenny (Parablennius thysanius), recorded in Hawaii, and the Horned Blenny (Parablennius intermedius)—might have been confused. I am an amateur, and the following is just my opinion.

This was my first time documenting this species. When I saw it, I thought it was just another blenny. I only took a few photos, mostly of poor quality.

After posting this to iNaturalist, naturalists in its community narrowed it down to the genus Parablennius. A little later, it was identified as Parablennius thysanius. After examining the available data in the app about P. thysanius, I realized that my animal did not match the observation photos. It appears to be a closer match to Parablennius intermedius, which has only been recorded in Australia, New Caledonia, Papua New Guinea, and the Solomon Islands.

As a complete amateur with low-quality photos of the animal, I decided to “stay in my lane” and accept that this is an animal, though recorded here at Kawaihae Harbor for the first time, it was not the first of its kind in Hawaii. Soon, doubts started to creep in. In a proper scientific manner, I investigated further. I have prepared my case here.

When unsure, ichthyologists often count the fish’s fin spines, right? I counted the fins I could see on my specimen, and the dorsal fin spines were close to the number listed for P. intermedius, about eight.

Short description Identification keys | Morphology | Morphometrics
Dorsal spines (total): 7; Dorsal soft rays (total): 16 – 17; Anal spines: 2; Anal soft rays: 18 – 20
(https://www.fishbase.se/summary/56925)

Short description Identification keys | Morphology | Morphometrics
Dorsal spines (total): 12; Dorsal soft rays (total): 14 – 15; Anal spines: 2; Anal soft rays: 16 – 17.
(https://www.fishbase.se/summary/46422)

I suggested again in the comment section of iNaturalist whether P. thysanius was misidentified (you can see the discussions here). Once more, the naturalists didn’t budge. The problem of confusing a visually similar species based on previous observations in the same area started to become clear. It’s easy to see that factors like using photos, especially poor-quality ones, can impact species identification. This misidentification then spreads, much like misinformation fueled by social media likes and shares.

Luckily, the species reappeared at the end of May 2025 and again at the end of August 2025, confirming that they are alive and reproducing in Kawaihae Harbor. This is encouraging news. There will be more chances for me to gather better photos of it. These fish are challenging to spot and photograph due to their small size and excellent camouflage. Both are approximately 1cm to 1.5cm in length. I had trouble keeping track of them. I pointed the camera in the general area where I saw movement and captured them by pure luck. 

 Until real scientists determine whether this species is Parablennius thysanius or intermedius, I will keep calling it P. intermedius.

iNaturalist, though with some limitations, is an excellent platform to motivate amateurs like me to document species around us and connect with more experienced scientists and naturalists.

If there’s even a small chance to be the first to record a new species in my little world at Kawaihae Reef, I will gladly take it. It is fun.