Tag: otolith

NOAA Teacher at Sea

David Madden

Aboard NOAA Ship Pisces

July 15-29, 2019

Mission: South East Fishery-Independent Survey (SEFIS)

Geographic Area of Cruise: Atlantic Ocean, SE US continental shelf ranging from Cape Hatteras, NC (35°30’ N, 75°19’W) to St. Lucie Inlet, FL (27°00’N, 75°59’W)

On board off the coast of North Carolina – about 45 miles east of Wilmington, NC (34°18’ N, 77°4’ W)

Date: July 27, 2019

Weather Data from the Bridge:

Latitude: 34°18’ N
Longitude: 77°4’ W
Wave Height: 3-4 feet
Wind Speed: 6.68 knots
Wind Direction: 42°
Visibility: 10 nm
Air Temperature: 28.0°C 
Barometric Pressure: 1022.4 mb
Sky: Partly cloudy

Science and Technology Log

Today, with the help of friends Zeb and Todd, I’d like to take a deep dive into the mission of this cruise.  Starting with the fish work up process aboard Pisces, first explained in blog #3.  Below is a picture flowchart I drew up to help visualize what’s going on. 

This sequential process is rather straight forward following steps 1-8, rinse (the gear) and repeat. It’s the before and after; what comes before step 1 and after step 8, that’s important; How and where is the data used.  If you follow along into steps 9, 10, 11… you start with the laboratory analysis of the biological samples – otoliths and gonads – used to age the fish, and determine reproductive activity and spawning seasons, respectively.  This information is vital to proper management of fisheries.  Here’s why. 

This cruise, and SEFIS in general, originally came into existence because of red snapper.  Scientists determined around 2009 that the red snapper population in the SE Atlantic was at historically low levels.  Strict regulations were put in place to help the species rebound.  This on its own was a good measure, but only one step.  In order to assess the effect of the regulations, scientists would have to monitor the abundance of red snapper in the region.  However, charting changes in abundance would not be enough with this species (or with many others) due to the nature of its life cycle and reproduction.  See, all populations have a natural age structure balance.  This includes species specific traits – like its survivorship curve (how likely it is for an individual to die at different points in their life – for red snapper and many other reef-associated species it’s incredibly high at their larval and juvenile stages).  It also includes pertinent developmental characteristics such as when the species is reproductively mature.  Like many similar fish, older, mature red snapper have greatly increased reproductive potential, also known as fecundity.  So while the population has been bouncing back in terms of numbers, the number of older, mature, more fecund fish is still considerably lower than historical levels; thus the population is still recovering.  *this information is gathered from the data collected by scientist here on our SEFIS mission, and others like them. 

The next step is to share this data with other scientists who will then, in conjunction with other information on the species, analyze the data and bring the results and conclusions of their analyses to policy makers (FYI, the government is moving towards making governmentally gathered scientific data available to the public).  Discussion ensues, and climbs the political decision-making-ladder until allowable catch regulations are determined.  Florida fishers, check here for your current snapper regulations or maybe this Fish Rules app will help.  Fish safe, my friends!

Ultimately this is a tricky and tangled issue of sustainability.  Commercial fishermen are understandably upset, as this can threaten their livelihood.  Although real, this concern is inherently short sighted, as their long term earnings depend on healthy and robust populations, and ecosystems.  The difficult part is to gather the necessary scientific data (very challenging, especially for marine organisms) and marry that to the many financial, social, and political concerns.  Comment below with thoughts and suggestions.  And while you’re at it, here’s a lovely and quick (fish-related) tutorial overview of this situation in general – the tragedy of the commons – and the challenges of managing our resources. 

A quick note about otoliths.  Within the fish processing protocol (above) – the most satisfying part is otolith extraction.  On board competitions abound: people vie for first chair (the spot in the lab that’s the coolest and best lit) and for the sharpest knives and scissors.  Much like a wild west showdown, most important is fastest extraction times.  Dave H opts for the classic chisel-through-the-gills technique, while the rest of us opt for the saw-through-the-skull-with-a-knife-and-crack-the-head-open-just-behind-the-eyes technique.  While Brad looks to perform the “double-extraction” – both otoliths removed in the tweezers at the same time, I look to perform the please-don’t-slice-my-hand-open extraction.  The quest for otoliths is usually straight forward.  But sometimes an ill-sliced cut can leave you digging for the tiny ear bones forever. 

This leaves us with: Why otoliths?  These tiny little ear bones help function in the fish’s vestibular system.  That’s a fancy way of saying the balance and orientation system of the fish.  They help vertebrates detect movement and acceleration, and they help with hearing.  These little bones help you determine your head and body orientation – turn your head sideways, it’s your otoliths who will send the message.  All vertebrates, including you, gentle reader, have them.  This makes me wonder if folks with exceptional balance and proprioception and court awareness have bigger otoliths?  Fish requiring more balance, those that sit and wait to hunt vs. those that swim predominantly in straight lines, have bigger otoliths. 

Otoliths are made of layered calcium carbonate (side question – does ocean acidification impact otolith formation?  Like it does with other calcium carbonate structures in the ocean?)  The fish secretes new layers as it ages: thicker layers during good times, thinner layers during lean times – correlated with summer and winter seasonality – just like with tree rings.  Once you dig out the otoliths, they can be analyzed by on-shore scientists who slice ‘em in half and take a really thin slice, deli-meat-style.  Voila! You can then count up the rings to tell how old the fish is. 

Retrieved from https://www.researchgate.net/publication/255711740_The_Ecology_of_Atlantic_Cod_Gadus_morhua_in_Canadian_Arctic_Lakes

Personal Log:

I’ve been continuing my work aboard the Pisces.  Lately the focus has been on conversations with scientists and ship personnel.  The source of most of today’s blog came primarily from conversations with Zeb and Todd.  They were both super helpful and patient in communicating the goals and mission of this cruise and SEFIS.  I’m also trying to contribute some things that might be useful to the NOAA scientists after the cruise is completed, and things that will be helpful to my students now and during the school year – like the drawings and diagrams, along with some upcoming videos (topics include: CTD color and pressure, Underwater footage featuring a tiger shark and hammerhead shark, Waves, All Hands on Deck, and a general cruise video). 

The food and mood of the cruise continues to be good.  * note: my salad eating has taken a hit with the expiration of spinach and leafy greens – it’s amazing they lasted as long as they did – the stewards, Rey and Dana, are amazing! 

General Updates:

1. The other night I had my first bit of troubled sleeping.  The seas were roaring!  Actually, just about 6 feet.  But it was enough to rock the boat and keep me from falling asleep.  It was almost a hypnic jerk every time the ship rolled from one side to the other.  Special sensations for when my head dipped below my feet. 
2. Two more book recommendations:  a. Newberry Book Award Winner: Call it Courage, by Armstrong Sperry.  I loved this book as a little boy.  I did a book report on it in maybe the 2^nd or 3^rd grade.  I spent more time drawing the cover of the report than I did writing it.    B.  A few years ago I read The Wave, by Susan Casey.  Great book about the science of waves and also the insane culture of big wave surfers. 
3. I haven’t seen all that much lately in terms of cool biodiversity.  The traps did catch some cute swimming crabs, a lionfish, and a pufferfish.   * more below.
4. Zeb won the Golden Sombrero Award the other day.  This is a momentous achievement awarded to a chief scientist after six consecutive empty fish traps!
5. Lauren crafted us an extra special tie-dye octopus named Oscar.  He’s wearing the Golden Sombrero in the photo above.     
6. Only 2.5 days till I’m back home.  Can’t wait to see my family. 

Neato Facts =

Back to general update #3 and today’s neato fact.  Both lionfish and pufferfish are toxic.  But are they poisonous? Or venomous?  Wait.  What’s the difference?  Both poisons and venoms are characterized as toxins, and often they are used interchangeably.  The distinction lies in the means of entry into your body.  Venoms get into you via something sharp – you’re either bitten with fangs or stung with stingers or spines.  Examples include our friend the lionfish, snakes, and bees.  Poisons, conversely, get into you when you eat it.  Examples include pufferfish, poison dart frogs,

Here’s a simple way to remember: Injection = Venom, Ingestion = Poison.  Click these links for interesting lists of poisonous animals, poisonous plants, and venomous animals. 

Please let me know if you have any questions or comments.