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My name is Natalie Slayden. I am a Master’s student at Nova Southeastern University working in Dr. Tracey Sutton’s Oceanic Ecology Lab. I am studying the age and growth of deep-pelagic fishes, with case studies of meso- and bathypelagic species from the Gulf of Mexico.
All fishes have three pairs of otoliths. Otoliths are often referred to as ear stones and are located in the cranial cavity of fishes. Otoliths come in different shapes and sizes depending on the species. Therefore, otoliths can be used to identify fish species. Fishes have otoliths to help them detect sound & orient themselves in the water column. Otoliths can tell us a lot about a fish’s life history and they can also be used to determine age.
Left: Both sides of an otolith from the species Ceratoscopelus warmingii (Rivaton & Philippe, 1999). Right: Awesome picture of a Ceratoscopelus warmingii taken by Danté Fenolio.
Have you ever heard of tree rings? Trees have rings that can be counted to reveal how old they are. Otoliths have rings too! These rings can be formed daily, monthly, yearly, or during events such as feeding. Like tree rings, otolith rings can be counted to determine age. Most previous research has focused on aging coastal fishes. Now, I am working to age some mesopelagic (200 – 1000 m) and bathypelagic (deeper than 1000 m) fishes.
Above: The otolith rings of three different species (Gartner, 1991)
Fisheries have become interested in deep-sea fishes to utilize them as feed for aquaculture and as oil for omega dietary supplements. Since they are a target for fisheries, it is important that we understand how long these deep-sea fishes live. Some deep-sea fishes have rings that are formed daily. Most of these fishes with daily rings perform a daily diel vertical migration, meaning they swim from the depths up towards the surface waters at night to feed and then swim back down to the depths at dawn to avoid visual predators. Lanternfishes are one group of fishes that undergo this migration pattern and usually have an age of one year or less. We think that the daily rings are formed due to light or temperature changes that occur during their daily vertical migration. However, for fishes that do not vertically migrate and remain at depth, it is uncertain what their otolith rings represent. Are they daily or yearly? Could they represent a single meal?
So, for my thesis project I will attempt to determine what an otolith ring represents for a non-vertically migrating deep-sea fish. Second, I will be describing the otolith ring patterns and correlating those patterns to the life history of my case study fishes. Lastly, I will be providing age estimations for a number of mesopelagic and bathypelagic fishes.
Hello, everyone! My name is Kristian Ramkissoon, and I am a graduate student working in the Oceanic Ecology Lab with Dr. Tracey Sutton. As a member of the lab, I am currently studying the species composition, abundance, and vertical distribution of the deep-sea fish genus Cyclothone, whose combined numbers make it the most abundant vertebrate on the planet. This study of Cyclothone in the Gulf of Mexico is one of the first of its kind. So what are Cyclothone? The name Cyclothone refers to a specific genus of fish which includes a number of different species. They are more commonly known as bristlemouths. Below are some of the more common species that we have collected in the Gulf of Mexico.
From left to right:(Top Row) Cyclothone pseudopallida, Cyclothone braueri,
(Bottom Row) Cyclothone obscura, Cyclothone pallida
Bristlemouths are close relatives of another abundant group of deep-sea fishes, the dragonfishes, and can similarly be found within the meso- and bathypelagic zones of the ocean. Unlike their more infamous cousins, however, Cyclothone are much smaller in size and much less active (many of the Cyclothone we encounter on our cruises are hardly an inch long!)
Cyclothone pallida against a ruler and under the microscope.
Collectively, these fishes have a near-ubiquitous distribution, with various species found throughout the world’s oceans. This worldwide presence, along with their status as the most abundant known vertebrate, make understanding Cyclothone important for understanding the ecology of the deep sea. As a part of my research into the world of bristlemouths, I spent a lot of time learning the unique features that distinguish each species from one another. Some of the common traits that I used to distinguish between different Cyclothone species were skin color, tooth shape, and gill morphology. To date we have identified thousands of individual Cyclothone down to the species level, keeping close counts and measures of each!
Pigmentation found on the head of (A) Cyclothone alba, (B-C) Cyclothone atraria, (D-F) Cyclothone braueri, and (G-J) Cyclothone pseudopallida.
Body, pigmentation, and photophores of Cyclothone pseudopallida.
So far, my research has revealed quite a few interesting things about these tiny denizens of the deep! For one, we have confirmed that Cyclothone in the Gulf of Mexico, similarly to those elsewhere in the world, do not vertically migrate. Additionally, the taxonomic data collected, in combination with data from the MOCNESS (Multiple Opening Closing Net and Environmental Sensing System) seem to suggest that all six species commonly found within the first 1500 meters of the northern Gulf of Mexico occupy relatively tight and distinct depth ranges. This information tells us that Cyclothone, unlike many other deep-living predators who migrate daily, may subsist entirely on what is found at their respective depth ranges (in the deep, this can be very little!). In addition, we are attempting to assess the impact that hydrographic features such as the Loop Current and eddies formed by it may have on the distribution of Cyclothone within the Gulf of Mexico.