NOAA Teacher at Sea
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
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.
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.
The length for each fish in the trap is noted, using a metrically scaled fish board. Not all fish are kept for further processing.
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.
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.
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.
Each fish is weighed, and the weight is noted in grams. The scale is periodically calibrated to be sure the fish is weighed accurately.
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.
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.
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.
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.
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.
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.
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:
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.