Stephen Kade: The Shark Cradle and Data Collection, August 8, 2018


NOAA Teacher at Sea

Stephen Kade

Aboard NOAA Ship Oregon II

July 23 – August 10, 2018

 

Mission: Long Line Shark/ Red Snapper survey Leg 1

Geographic Area: 31 41 010 N, 80 06 062 W, 30 nautical miles NE of Savannah, North Carolina

Date: August 8, 2018

 

Weather Data from Bridge:

Wind speed 11 knots,
Air Temp: 30c,
Visibility 10 nautical miles,
Wave height 3 ft.

Science and Technology Log

Normally you wouldn’t hear the words shark and cradle in the same sentence, but in our case, the cradle is one of the most important pieces of equipment we use each day. Our mission on the Oregon II is to survey sharks to provide data for further study by NOAA scientists. We use the long line fishing method where 100 hooks are put out on a mile long line for about an hour, and then slowly hauled up by a large mechanical reel. If a shark is generally three feet and weighs 30lbs or less, it is handled by hand to carefully unhook, measure and throw back. If the shark is much larger and cannot be managed safely by hand, it is then held on the line by the ships rail until it can be lifted on deck by the cradle to be quickly measured, tagged, and put back into the ocean.

The shark cradle

The shark cradle

The shark cradle is 10 ft. long, with a bed width of roughly 4 feet. It is made from thick aluminum tubing and strong synthetic netting to provide the bed for the shark to lie on. It is lifted from the ship’s deck by a large crane and lowered over the ships rail into the ocean. The shark is still on the line and is guided by a skilled fisherman into the cradle. The crane operator slowly lifts the cradle out of the water, up to the rail, so work can begin.

A team of 3 highly skilled fishermen quickly begin to safely secure the shark to protect it, and the team of scientists collecting data. They secure the shark at 3 points, the head, body and tail. Then the scientists come in to take 3 measurements of the shark. The precaudal measurement is from the tip of nose to the start of the tail. The fork measurement is from the tip of the nose to the fork of the tail (the place where the top and bottom of the tail meet). Finally there is a total length taken from the tip of the nose to the furthest tip of the tail.

When all measurements are complete, a tag is then placed at the base of the first dorsal (top) fin. First a small incision is made, and then the tagger pushes the tag just below the skin. The tag contains a tracking number and total length to be taken by the person who finds the shark next, and a phone number to call NOAA, so the data can recorded and compared to the previous time data is recorded. The yellow swivel tags, used for smaller sharks, are identical to ones used in sheep ears in the farming industry, and are placed on the front of the dorsal fin. The measurements and tag number are collected on the data sheet for each station. The data is input to a computer and uploaded to the NOAA shark database so populations and numbers can be assessed at any time by NOAA and state Departments of Natural Resources.

removing hook

A skilled fisherman removes the hook so the shark can be released.

longline

The longline is mile long and carries up to 100 hooks.

The shark is then unhooked safely by a skilled fisherman while the other two are keeping the shark still to protect both the shark and the fishermen from injury. The cradle is then slowly lowered by crane back into the ocean where the shark can easily glide back into its environment unharmed. The cradle is then raised back on deck by the crane operator, and guided by the two fishermen. All crew on deck must wear hardhats during this operation as safety for all is one of NOAA’s top priorities. This process is usually completed within 2 minutes, or the time it took you to read this post. It can happen many times during a station, as there are 100 hooks on the one mile line.

 

 

Personal Log

It is amazing for me to see and participate in the long line fishing process. I find it similar to watching medical television shows like “ER” where you see a highly skilled team of individually talented members working together quickly and efficiently to perform an operation. It can be highly stressful if the shark is not cooperating, or the conditions aren’t ideal, but each member always keeps their cool under this intense work. It’s also amazing to see the wealth of knowledge each person has so when an issue arises, someone always knows the answer to the problem, or the right tool to use to fix the situation, as they’ve done it before.

Animals Seen Today: Sandbar shark, Tiger shark, Sharpnose Shark, Sea Robin, Toadfish, Flying Fish

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