NOAA Teacher at Sea
David Walker
Aboard NOAA Ship Oregon II
June 24 – July 9, 2015
Mission: SEAMAP Bottomfish Survey
Geographical Area of Cruise: Gulf of Mexico
Date: July 3, 2015
Weather Data from the Bridge
Weather has fortunately continued to be calm. The only main deviation from clear skies has been haziness (symbolized “HZ” on the above weather log from 7/2/15). On 7/2/15, sky condition varied from FEW (3-4 octas) in the very early morning, to SCT (3-4 octas) and BKN (5-7 octas) at midday and afternoon, to SCT (3-4 octas) in the evening and night. Swell waves have varied throughout the past couple of days, from less that 1 meter to around 3 meters in height.
Science and Technology Log
The past few days honestly blend completely together in my mind. I feel as though I have reached an equilibrium of sorts on the boat. The night shift has proceeded normally – station to station, trawl to trawl, CTD data collection at each station, plankton collected periodically throughout the shift. Certain trawl catches have been exceptionally muddy, which poses a further task, as the organisms must first be separated from all of the mud and cleaned, before they can be identified.
In addition, on Day 6, the trawl net was damaged on a couple of occasions. I’ve realized that a trawl rig is quite the complicated setup. The trawling we are doing is formally called “otter trawling”. Two boards are attached at the top of the rig to aid in spreading out the net underwater. To allow the net to open underwater, one of the two lead lines of the net contains floats to elevate it in the water column. A “tickler chain” precedes the lead lines to stir fish from the sea floor and into the net. The fish collected by the net are funneled into the terminating portion of the net, called the “cod end”. FMES Warren Brown is an expert when it comes to this entire rig, and he is in charge of fixing problems when they arise. On Day 6, Warren had to fix breaks in the net twice. With help from Lead Fisherman Chris Nichols and Skilled Fisherman Chuck Godwin, new brummel hooks were attached to the head rope for one of the door lifting lines, and a new tickler chain was installed.
I also learned a lot more of the specifics involved in the workup of the plankton catch. The dual bongo contains two collection nets in parallel. Plankton is removed from the cod ends of these nets, but not combined. The plankton from the left bongo is transferred to a mixture of formaldehyde (10% v/v) and sea water for preservation. The plankton from the right bongo is transferred to 95% ethanol. The reason for this is that different solvent mixtures are needed to best preserve different parts of the plankton in the sample. The formaldehyde solution is best for fixing tissue, yet it tends to dissolve hard parts (for example, otoliths, discussed below). The ethanol solution is better for preserving hard parts (bones, cartilage, etc.). This explains the need for two bongos. Workup of collected plankton from the Neuston net is similar, except many non-plankton species are often collected, which have to be removed from the sample. Highlight non-plankton species from the past couple days have been sailfin flyingfish (Parexocoetus brachypterus) and a juvenile billfish (Istiophoridae). Neuston-collected plankton is transferred to 95% ethanol. This solvent is the only one needed here, as only DNA analysis and stock assessment are conducted on Neuston-collected plankton. All plankton is shipped to Poland, where a lab working in collaboration with NOAA will analyze it. Samples are broken down according to a priority species list sent by NOAA.
The CTD survey is coming along nicely. Progress through July 1 is shown on the below bottom dissolved oxygen contour. Similar trends to those commented on in my last blog post continue to be observed, as a further area of hypoxia has been exposed near the coastline. You can see that our survey is progressing east toward Mississippi (we will finish this leg in Pascagoula, MI, though the survey will continue on to the Florida coast during Leg 3).
A couple of other distinct memories stand out in my mind from the past couple of days:
- Sexing “ripe” fish. Sometimes, certain species of fish are so fertile over the summer that certain individuals are deemed “ripe”. Instead of cutting into these fish, they can be more easily sexed by applying pressure toward that anus and looking for the expression of semen or eggs. One of the species for which this technique is most often applied this time of year is the Atlantic cutlassfish (Trichiurus lepturus). One must be careful, however, for as I found out, the gametes sometimes emit from the anus with much force, shooting across the room. It only takes wiping fish semen off of your face once to remember this forever.
- Flying fish. I saw my first flyingfish (Exocoetidae) during a plankton collection with the neuston net. The net would scatter the fish, and they would fly for cover, sometimes 10-15 meters in distance. Amazing.
- Preparing sand dollars. Interestingly, the sand dollars we caught (Clypeaster ravenelii) looked brown/green when they came out of the ocean. Sand dollars are naturally brownish, and in the ocean, they are most often covered in algae. We kept a couple of these organisms to prepare. To prepare, we first placed the sand dollars in a dilute bleach solution for awhile. We then removed them and shook out the sand and internal organs. We then placed them back in the bleach for a little longer, until they looked white, with no blemishes. The contrast between the sand dollar, as removed from the ocean, and this pure white is quite remarkable.
- Otoliths. Fisheries biologist Kevin Rademacher showed me a nifty way to remove the otoliths from fish. Otoliths, “commonly known as ‘earstones,’ are hard calcium carbonate structures located behind the brain of bony fishes,” which “aid fish in balance and hearing” (Florida Fish and Wildlife Conservation Commission). When viewed under microscope and refracted light, otoliths show a pattern of dark translucent zones (representing period of quick growth) and white opaque zone (representing periods of slower growth). By counting the white opaque zones (called “annuli”), fisheries biologists can estimate the age of the fish. Granted, this process differs for different fish, as different fish species have different otolith size. Accordingly, a species standard is always prepared (usually a fish raised from spawn, from which the otoliths are taken at a known age) to estimate the growth time associated with one whole annulus for the particular species. Sample otoliths are compared to the standard to estimate age. Otolith analysis also allows scientists to estimate “growth rates,…age at maturity, and trends of future generations” (Florida Fish and Wildlife Conservation Commission). On this survey, we only take otoliths from fish that are wanted for further laboratory analysis, but are too large to store in the freezer. On some surveys, however, otoliths are removed from all fish caught. I got to remove the otoliths from a large red snapper (Lutjanus campechanus). The first step is to make an incision to separate the tongue and throat from the lower jaw. The hand is then inserted into the hole created, and using a fair bit of force, the throat and gills are ripped away from the head to expose the vertebrae. The gills are then cut from the base of the vertebrae, to expose the bony bulb containing the sagittal otoliths. Diagonal cutters are then used to crack open the boney bulb containing the sagittal otoliths, and the otoliths are removed using forceps.
Personal Log
I am still feeling great on the boat. The work is quite tiring, and I usually go straight to the shower and the bed after my shift ends. Interestingly, I think I’m actually gaining quite a bit of weight. The work is hard and the food is excellent, so I’ve been eating a bunch. I’ve been getting 7-8 hours of sleep a night, which is more than I normally get when I am at home, especially during the school year. One thing I have been noticing ever since the trip started is that I have been having quite nightmarish dreams every night. This is rare for me, as I usually either don’t have dreams or can’t remember the ones that occur. I initially thought that this might be due to the rocking of the boat, or maybe to the slight change in my diet, but I think I’ve finally found the culprit – Dramamine®. Research has indicated that this anti-motion sickness drug can cause “disturbing dreams” (Wood, et al., 1966), and I have been taking this medication since the trip started. This hypothesis is consistent with the observation that my nightmares lessened when I reduced my daily Dramamine® dose from 2 pills to one. I finished Everything is Illuminated and have begun a new novel (Tender is the Night, by F. Scott Fitzgerald). I am now well into the second week of my trip!
Did You Know?
Earrings can be made from fish otoliths (ear stones). These seem to be quite popular in many port cities. Check out this article from the Juneau (Alaska) Empire Newspaper.
Notable Species Seen
