Carmen Andrews: Transforming Fish into Data, July 15, 2012

NOAA Teacher at Sea
Carmen Andrews
Aboard R/V Savannah
July 7 – 18, 2012

Mission: SEFIS Reef Fish Survey
Location: Atlantic Ocean, off the coast of Cape Canaveral, Florida
Date: July 15, 2012

Latitude:      28 ° 50.28   N
Longitude:   80 ° 26.26’  W       

Weather Data:
Air Temperature: 28.6° C (83.48°F)
Wind Speed: 18 knots
Wind Direction: from the Southeast
Surface Water Temperature: 27.6 °C (81.68°F)
Weather conditions: Sunny and Fair

Science and Technology Log

How are fish catches transformed into data? How can scientists use data derived from fish to help conserve threatened fish species?

The goal of the Southeast Fishery-Independent Survey or SEFIS is to monitor and research reef fish in southeast continental shelf waters.  Marine and fisheries scientists have developed sophisticated protocols and procedures to ensure the best possible sampling of these important natural resources, and to develop fisheries management recommendations for present and future sustainability.

During the cruise, important commercial fish in the snapper and grouper families are caught over as wide an area as possible; they are also taken in large enough numbers that they can be worked up into statistically reliable metrics. In addition to counts and measurements, biological samples are also taken at sea for future analysis in land-based research labs.

Gag grouper ready for its work up

Gag grouper ready for its work-up

Scientists strive to render an informative snapshot of reef fish stocks in a given time interval. Reports that analyze and summarize the data are submitted to policy-makers and legislators to set fisheries rules, restrictions and possible quotas for commercial and sports fishermen.

After fish are caught and put on ice, processing includes several kinds of measurement that occur on deck. This data is referred to as ‘Length Frequency’. Tag information from the trap follows the fish through all processing.  Aggregate weight measurements for all the fish of one species caught in a trap are made and recorded in kilograms.

David is weighing the gag grouper, with Adam P. looking on

David is weighing the gag grouper, with Adam P. looking on

The length for each fish in the trap is noted, using a metrically scaled fish board. Not all fish are kept for further processing.

David measuring the length of the gag grouper

David measuring the length of the gag grouper

Species-specific tally sheets randomly assign which fish from the catch are kept and which ones are tossed back into the ocean. These forms, which specify percentages of fish identified as ‘keepers’, are closely consulted by the data recorder and the information is shared with the scientist who is measuring the catch.

Shelly is recording length frequency measurement data

Shelly is recording length frequency measurement data

Length frequency data entries

Length frequency data entries

Red Porgy keep/toss percentage sheet

Red Porgy keep/toss percentage sheet

Kept fish are put in a seawater and ice slurry. The others are thrown over the side of the boat.

Age and reproductive sampling are done next in the wet lab.

Small yellow envelopes are prepared before fish work up can begin. Each envelope is labeled with cruise information, catch number, fish number, and the taxonomical name of the fish, using  binomial nomenclature of genus and species.

Adam P. and Shelly labeling envelopes and plastic specimen containers

Adam P. and Shelly labeling envelopes and plastic specimen containers

A small color-coded plastic container (the color indicates fish species tissue origin), with the fish’s source information riveted at the top, is also prepared. This container will store fish tissue samples.

The fish trap catch number is documented on another data form, along with boat and science team identification, collection method and other important information about the circumstances surrounding the fish catch.  Each species’ data is separately grouped on the data form, as individual fish in a catch are sequentially numbered down the form.

Me, transcribing fish weight & length data

Me, transcribing fish weight & length data

Each fish is weighed, and the weight is noted in grams. The scale is periodically calibrated to be sure the fish is weighed accurately.

Vermilion snappers and scamp, labeled and  ready for dissection

Vermilion snappers and scamp, labeled and ready for dissection

Three length measurements that are made: standard length (SL), total length (TL), and if the fish species has a fork tail — fork length (FL). The fish is laid, facing left on a fish board. The board is long wooden plank with a metric measuring scale running down the center.

Standard length does not include the caudal fin or tail. It begins at the tip of the fish’s head; then the fish measurer lifts the tail up slightly to form a crease where the backbone ends. Standard length measurement includes the fish’s head to end of backbone dimension only. Total length is the entire length of the fish, including the caudal fin. In fork-tailed species, the fork length measurement begins at the fish’s snout and ends at the v-notch in the tail.

Fish length measurements

Fish length measurements

Source: Australian Government – Department of Environment, Water, Population and Communities

Part of the dissection of every fish (except gray triggerfish) is the extraction of  otoliths from the fish’s head. An otolith is a bone-like structure made of calcium carbonate and located in the inner ear of fish. All vertebrates have similar structures that function as gravity, balance, movement, and directional indicators. Otoliths help fish sense changes in horizontal motion and acceleration.

To extract the otoliths, the scientist makes a deep cut behind the fish’s head and pulls it away from the body. The left and right otoliths are found in small slits below the brain. They must be removed carefully, one at a time with forceps. They can easily break or slip into the brain cavity.

Red snapper with removed otolith

Red snapper with removed otolith

Otoliths reveal many things about a fish’s life. Its age and growth throughout the first year of its life can be determined. Otoliths have concentric rings that are deposited over time. The information they show is analogous tree ring growth patterns that record winter and summer cycles. Other otolith measurements can determine when the fish hatched, as well as helping to calculate spawning times in the fish’s life.

The oxygen atoms in calcium carbonate (CaCO3) can be used to assay oxygen isotopes. Scientists can use these markers to reconstruct temperatures of the waters the fish has lived in. Scientists also look for other trace elements and isotopes to determine various environmental factors.

Each pair of otoliths is put into the small labeled yellow envelope.

The otoliths on the gray triggerfish are too small to be studied, so the spine from its back is collected for age and growth analysis.

Spine removed from a gray triggerfish

Spine removed from a gray triggerfish

The last step standard data collection is determining the sex and maturity of the fish. The fish is cut open at the belly, similar to preparing the fish as a filet to eat it.

Making a cut into a vermilion snapper

Making a cut into a vermilion snapper

If the fish is big, the air bladder must be deflated. The intestines are moved or cut out of the way. The gonads (ovaries and testes) are found, and the fish can be identified as a male or female. (Groupers can be hermaphroditic.) The fish’s stage of maturity can also be determined this way.  Maturational stages can be classified with a series of codes:

U = undetermined

1 = immature virgin (gonads are barely visible)

2 = resting (empty gonads – in between reproductive events)

3 = enlarging/developing (eggs/sperm are beginning to be produced)

4 = running ripe (gonads are full of eggs/sperm and are ready to spawn)

5 = spent (spawning has already occurred)

Dissected gonad specimens are removed from the fish and placed in a plastic containers, snapped shut and stored in a formalin jar to preserve them. These preserved samples will be analyzed later by histology scientists. Histology is the science of organ tissue analysis.

Dissected fish gonads

Dissected fish gonads

Red snappers have their fins clipped to provide a DNA sample. They may also have their stomachs removed and the contents studied to better understand their diets.

Video data from the underwater cameras is downloaded in the dry lab. This data will be analyzed once scientists return to their labs on land.

Personal Log

Many different kinds of echinoderms and other invertebrates have been pulled up in the fish traps. Several are species that I’ve never seen before:

Basket Star

I am holding a basket star. It is a type of brittle star in the echinoderm phylum.

A red sea star

A red sea star

Spikey sea star

Spikey sea star

Small crab, covered in seaweed, shell and sand

Small crab, covered in seaweed, shell and sand

We also catch many unusual large and small fish in the traps and on hooks. Several of these have been tropical species that I’ve only seen in salt water aquariums.

Lizardfish

Lizardfish

Sargassumfish

Sargassumfish

Hooked blacktip shark

Hooked blacktip shark

Scrawld Filefish

Scrawld Filefish

Spotted butterflyfish

Spotted butterflyfish

Jack knife fish

Jack knife fish

Walter Charuba: Red Skies at Night: July 21st, 2011

NOAA Teacher at Sea
Walter Charuba
Aboard R/V Savannah
July 18 — 29, 2011

Mission: Reef Fish Survey
Geographical Area: Southeast Atlantic Ocean
Date: July 21, 2011

Science and Technology Log

There is an old sailor’s proverb: “Red Sky at night, it will be bright” or “sailors take flight“ or something like that. I just know that I live by this saying and it has caused many a captain to throw away their weather charts. There was a beautiful red sunset last night and I stood at the bow or stern (I am down to two boat locations now) in complete admiration. However, when I started my shift in the morning there was a front moving in with rain clouds and lightning. I must admit I have been pretty calm most of the trip and this has not been due to the Dramamine. Seeing these clouds caused my imagination to get the better part of me, which of course would be the part that includes my brain.  I had images of “The Great Wave” by Hokausai racing in my head.  This outlook was ridiculous because there weren’t even white caps on the waves. The storm never hit us and the day turned out to be excellent.

Dolphins chasing flying fish at night

Another reason last night was special was because I was able to view some dolphins at a very close distance.  First Mate, Michael Richter, made it quite clear that no one was supposed to walk around the boat alone at night, especially the dark upper deck , and especially on the railings. So after daylight, we are limited to the lighted lower deck.  As I was reviewing my constellations, the light seemed to attract these flying fishes. I do not know if this is true, because correlation isn’t always causation, but it looked true.  As I was staring at the flying fishes, a large splash startled everyone. It was a spotted dolphin and a calf jumping for the flying fishes. The dolphins jumped around for about twenty minutes until we took off to our next destination. It was kind of like our own little Sea World, except natural. It was a perfect way to end the night.

Here I am (right) preparing to help with the trap collection

Morning was the time to not only see, but capture, new creatures. My last blog described the deployment of traps, but now I will write about the retrieval of traps. Science Watch Chief, David Berrane termed this “action time.”  The two flotation buoys we drop are significant because, after “soaking” a trap for 90 minutes, the boat returns to these devices and a crew member has to throw a grappling hook at a line between the buoys. We then quickly pull the buoys in next to the boat.  The buoys are lifted up, the line is connected to a “hauler,” and a trap is pulled on board. This may sound simple but it is actually a five person task. The task is very intense and focused because people may trip over the buoys or ropes, or the trap’s line can snap due to weight or current. Hopefully the trap will be filled with fish and the cameras will record useful data from depths ranging from 25 to 83 meters. As soon as the trap is brought on board, the fish are collected and the cameras are disconnected.

The cameras used on the fish traps

The video survey of the reef is just as important as capturing fish, as cameras can assess the population of species that do not go in traps. Zeb Schobernd, the video watch commander, and I do salute him, downloads all the data on board for further viewing during the off season. Imagine all the viewing that has to be done? For instance fifteen videos were taken in one day of our ten day cruise, and there are four or five missions a year. To avoid reef video insanity, the data is viewed in thirty second intervals which is still a great deal of work.

Fish brought on board are immediately classified to species, and then measured individually. Measurement data are called “length frequency,” and hundreds of fish could be measured from one trap. According to a random tally sheet, certain fish are kept to collect “age and growth” data. Again, this could be hundreds of fish. In the ship’s “wet lab,” fish are then dissected. Most fish have a pair of “otolith” bones (i.e., ear stones) in their head.  Otoliths are collected at sea, but sent to a lab where they will be examined under a microscope.  When otoliths are cut by a delicate saw, visible rings tell the age of a fish, similar to how the rings visible on a tree stump can tell the age of a tree. Fish are further dissected to check the condition of their reproductive systems.

In the next blog I will I write about the “CTD” device.