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My name is Nina Pruzinsky. I am a Master’s student at Nova Southeastern University, where I am working under Dr. Tracey Sutton. Also, I am a graduate research assistant in Dr. Sutton’s Oceanic Ecology Lab, where I am studying the identification and spatiotemporal distributions of tuna early life stages (larvae and juveniles) in the Gulf of Mexico.
Tuna are ecologically, economically and recreationally important fishes. You may know them for their large size, high speeds, and highly migratory behaviors. Fishermen enjoy catching these are fish because they average 2.5 m in size and 250 kg in weight!! They are top-predators in many coastal and oceanic environments, feeding on fish, squid and crustaceans.
Check out this video of tuna from the Blue Planet II series.
Several species have been placed on the IUCN Red List of Threatened Species. For example, Northern Atlantic bluefin tuna is listed as endangered, yellowfin and albacares as near-threatened, and bigeye as vulnerable. Several tuna species spawn in the Gulf of Mexico due to its warm temperatures and unique hydrographic features improving the survival of their eggs and larvae.
So what exactly am I studying for my thesis?
First, I am identifying features that describe the early life stages of different tuna species. The morphology (“the study of form” or appearance of physical features) of tuna early life stages is poorly-described. Collecting fishes at these small size classes (3-125 mm SL) is very rare due to limited sampling across their wide-range of habitats. However, it is extremely important because if we do not know how to identify a fish when it is young, we cannot protect it and ensure it lives to its adult reproductive stage. So, my first task was to create an identification guide for these small fishes. The key features used for identification include: pigmentation patterns, body shape, ratios of different body parts, and fin ray counts.
To date, I have identified 11 different tuna species. These include: little tunny, blackfin tuna, bluefin tuna, yellowfin tuna, frigate tuna, bullet tuna, skipjack tuna, wahoo, Atlantic chub mackerel, Atlantic bonito, and king mackerel. Pictures of these fishes are included below. You can see how differently their early life stages look compared to their adult stages.
Larval and adult little tunny.
Larval and adult blackfin tuna.
Larval and adult king mackerel.
Larval and adult wahoo.
The second part of my project is to identify the spatiotemporal distributions of larval and juvenile tunas. Once we know what species we have, then we can identify where it is found, in what season it spawns, what type of environmental features it prefers, and so on. Basically, I am gaining knowledge about its habitat preferences, so we can help protect future populations and increase recruitment levels.
There are some small tuna species such as little tuna and blackfin tuna that do not have stock assessments nor management plans currently developed. Thus, learning about the environmental conditions that affect their distributions is essential in assessing their populations. It is evident that we still have a lot of knowledge to gain about these size classes.
This summer, I participated in an ichthyoplankton cruise in the Gulf of Mexico. Left: Jason and I are collecting organisms from the bongo net. Middle: I am holding a juvenile frigate tuna collected with a dipnet. Right: I am identifying a larval tuna under the microscope in the lab onboard.
Howdy! My name is Corinne Meinert and I am a Master’s student in marine biology at Texas A&M University in Galveston studying biodiversity of ichthyoplankton in the Northern Gulf of Mexico. When you break the word ‘ichthyoplankton’ down you get ‘ichthyo’ which means fish, and ‘plankton’ which means drifter, so all together the word refers to fish eggs and larval fish that drift in the ocean with the currents. Studying the biodiversity of these little fish is important because it can tell us how healthy the ecosystem is where they live; in general, the higher the diversity of fish, the healthier the ecosystem.
To give you an idea of how small these fish are, below is a picture of a snake mackerel (Gempylus serpens) on my finger:
In the lab, we use microscopes to visually identify our fish samples to the family level. For some families, such as tunas, billfish, and dolphinfish, we use genetics to identify the fish to species level. Over the past two years, we have collected and identified over 18,000 larval fish and have found a total of 99 different families. The most abundant families we have found are lanternfish (Myctophidae) and jacks (Carangidae), when combined, these two families make up of 25% of our total catch. Below are a few pictures of different families of fish we have collected (note: the third one is a tuna with another tuna inside of its stomach!):
We still have a lot to learn about larval fish. Understanding how abundant they are and where they live can help us make better management decisions for the future. If you want to learn more about ichthyoplankton and biodiversity, here are a few good webpages and videos to get started:
Information on ichthyoplankton: https://swfsc.noaa.gov/textblock.aspx?Division=FRD&id=6210
Information on biodiversity: https://www.youtube.com/watch?v=GK_vRtHJZu4
A compilation of other fish (and one invertebrate!) caught during DEEPEND sampling:
Last night we cruised towards our southern transect. We arrived at our first station and began sampling at sunrise (6am). We've hit 10 stations so far today! We collected many of our targeted species and more!
On the boat, we use a camera attached to our microscope to help us take pictures of the tiny fish. Here's some of our catch:
Alex found a siphonophore.
Cori, Travis and Jillian on deck and ready for the next tow!
All smiles here!
My name is Nina Pruzinsky. I’m out in the northern Gulf of Mexico with Texas A&M sampling for fish larvae on the R/V Pelican. We’ll be out here from July 1-5th. The scientists onboard include: Dr. Michelle Sluis (TAMUG), Jessica Lee (TAMUG), Travis Richards (TAMUG), Cori Meinert (TAMUG), Jillian Gilmartin (TAMUG), Alex Southernland (TAMUG), Jason Mostowy (TAMUG), Richard Jones (FAU) and Nina Pruzinsky (NSU).
We left the port at LUMCON at midnight on June 30th and traveled to the first station (Station 48) during the night. We started our sampling around 10am yesterday. We finished nine stations during the day and did two night tows. During the day we are using a neuston net and bongo nets to sample for larval fish. The neuston net tows for 10 minutes at the surface and the bongo nets sample to about 100 m depth. At night, we only tow the neuston net. This way, we can compare the differences between day and night tows at the same station. Additionally, Alex is sampling for gelatinous zooplankton (jellyfish) for genetic analyses, Jillian is Gtowing another plankton net to look at the community structure of zooplankton, and Travis is collecting water samples in order to characterize the food web in the Gulf.
Yesterday we caught tunas, billfish, dolphinfish, flyingfish, eel larvae, remora, frogfish, triggerfish, pufferfish, rough scad, lanternfish (at night) and more! Check out the pictures below! As you can see, all of our fish are extremely small!
Today we started sampling at sunrise around 6am and have completed three stations. We already caught some tuna and dolphinfish larvae!
Stay tuned for more pictures and updates on the cruise!
R/V Pelican before depature.
Larval dolphinfish (mahi-mahi).
Michelle and Cori preparing the neuston net.
Jillian setting up the plankton net along with the bongo nets.
We also were able to dip net a juvenile tuna last night for my thesis!