Saturday, January 23, 2021

A Peculiar Looking Fish by Austyn Morin

Stranded dead Gray Triggerfish on Great Island, Wellfleet
 on 11/21/2020 by Holly Kuhn

The Gray Triggerfish (Balistes capriscus), also known as a Leatherjacket or Taly, belongs to the Balistidae or the triggerfish family, containing about 40 species altogether. Their most identifiable feature is their front spiny dorsal fin, which gives the Gray Triggerfish its name because they use their front dorsal fin as a defense mechanism against predators. When threatened, the Gray Triggerfish will move into a rocky crevice and erect their front dorsal fin, locking them into place. The Gray Triggerfish has been known to become stranded on Cape Cod's beaches, so it is important to note other important physical features. Mainly since the physical characteristics of the Gray Triggerfish can change depending on age and sex. That way, if one is identified, you can take photos of it and take note of its location. In general they have large plate-like scales at the front of their body, but they become smoother and smaller towards the back of the fish. Triggerfish are compressed laterally, so they look somewhat like an oblong plate. The eyes of the Triggerfish are also set farther away from their mouth. They have two separate dorsal fins a spiny one in the front for defense and another one behind it. There is also an anal fin which is on the opposite side of the second dorsal fin. They also have a caudal or tail fin that can have elongated lobes in larger adults.


Dead stranded Gray Triggerfish on Cold Storage Beach, Truro, MA. 
Photo by Eric Joransen

Adults tend to be olive-gray and can have blue spots and lines on their upper body and dorsal fins and white spots near their lower body and fins.  In comparison, juveniles are more yellowish and have small violet dots. Gray Triggerfish call the waters of the East Atlantic from Nova Scotia all the way down to Argentina home. Triggerfish prefer areas with hard bottoms or reefs, and they live in bays or lagoons in depths up to 55 meters. Gray Triggerfish can weigh as much as 13 pounds. They can reach upto 28 inches in length and normally live around 11-15 years.

Spawning season for Gray triggerfish occurs between the months of April to August, and during this time, Triggerfish exhibit an exciting ability in their toolset. They change colors. Males become a more charcoal grey color while females become a more contrasting black and white. It is essential to keep in mind if you find a fish on the beach that looks like a Gray Triggerfish, but the colors seem off. After the fish have mated, it typically takes about 44-55 hours for the eggs to hatch. Once they hatch, unlike their adult counterparts who prefer to hang out near the water's bottom, juveniles live at a more shallow depth. These young Triggerfish are very closely connected with Sargassum, which is a type of Algae. In fact, Sargassum is so important to young Gray Triggerfish that juveniles' survival rates are directly correlated to the abundance of the Sargassum. So, future efforts to maintain the populations could be connected to monitoring the quantity of Sargassum.

Gray Triggerfish in open water
Photo posted by SpaceCoastDaily.com

An adult Gray Triggerfishes' favorite foods are Benthic invertebrates like mollusks, crabs, shrimp, sea urchins, and lobsters. In contrast, the juveniles tend to prefer hydroids, which are related to jellyfish, barnacles, and polychaetes, also known as bristle worms. Because of their preferred diet of shelled creatures Gray Triggerfish have very specialized incisor-like teeth to create holes on their shelled prey. Interestingly enough, Gray Triggerfish also show some exciting foraging behaviors while looking for prey. In a study done by Thomas Frazer, Triggerfish would direct a stream of water towards the sand to move the sand and reveal any hiding prey like sand dollars. They will then undulate their anal and dorsal fins to hover above the water to get their prey. As previously stated, Gray Triggerfish change their colors more dramatically during the spawning season. Still, they can also slightly change their color to better blend in with their surroundings. There is more interesting behaviour exhibited by Gray Triggerfish during extreme weather patterns. A recent study found that many fish species living close to the bottom of the ocean floor are actually affected by tropical storms. Researchers noted a change of movement behaviour of Gray Triggerfish during extreme weather conditions. Mainly that there was increased movement oftentimes to deeper water, just before or during the storms.

Live Sand Dollar, Long Point Beach, MA
Photo by Katarina Bingham-Maas

Due to their abundance and comprehensive range, they are a favorite for anglers both commercially and for recreation. There are two main stocks in the Atlantic: in the Gulf of Mexico and the South Atlantic. However, due to their popularity in 2018, the stock in the Gulf of Mexico was overfished. Today it is no longer currently considered to be overfished, and the population is rebuilding to target levels. Despite their popularity, there is no need for alarm because the fishing gear used for Gray Triggerfish has been shown to have a little environmental impact. As well the World Conservation Union does not consider the Gray Triggerfish to be threatened or endangered. There are regulations in place by the US government to make sure Gray Triggerfish populations remain sustainable, and because of this, Gray Triggerfish are an excellent choice for seafood. As an alternative for those who are looking for a more sustainable meat source. Or if you're looking for something new to try. Gray Triggerfish are also notorious among anglers for being bait stealers, especially those fishing for Red Snapper and Grouper.

Gray Triggerfish strandings are a visible event that occurs on Cape Cod. So, by starting the data collection process on where they are stranding. We can begin to better understand the role these peculiar fish play in our waters. For more information about Gray Triggerfish check out these links and Articles below.

This blog post by Austyn Morin, Senior at Stonehill College


Links to learn more about the Gray Triggerfish: