Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 9, 2018 (Day 1)*

*Note:these will be posted on a one-day delay, i.e., this report is for yesterday’s activities.

Hello again, and welcome to Weedlines !

Our first day at sea was a success; it’s nice when you can get off to a great start. We left the dock last night at midnight, and steamed due south of Mobile Bay towards a location (approximately 28°N, 88°W) where we hoped to findSargassumbased on remote sensing analyses. We woke to calm seas (< 1 foot), but relatively cloudy skies, which made scanning the horizon for Sargassuma bit difficult. Along this transit we encountered quite a few dolphins, including two large pods of approximately 30-40 individuals (we think maybe Pantropical Spotted Dolphins), and we even spotted the flukes of a whale in the distance just prior to it diving. Also along the way we encountered scattered clumps of Sargassum, but no larger, consolidated mats or weedlines–at least not until later in the afternoon!

Brown booby

A brown booby leads the way to the largest Sargassum mat we have encountered on this project. (Photo: Eric Haffey)

Around 1430 we came across the largest mats we’ve encountered in the Gulf today, at least on this project. Though late in the day, we decided to sample and do our best to get as much done as possible. We started with a neuston “dip” through a thick part of the mat, and though we collected a lot of Sargassum, there were relatively few fish, including an Ocean Triggerfish and Sargassumfish. Notably, this Sargassummat was very “thick”; we estimated that the canopy thickness ranged anywhere from 20-50 cm. So perhaps our neuston net was not the most effective sampler (we plan on trying again tomorrow).

Sargassum washing

The Fisheries Oceanography Lab washes down Sargassum, inspecting for fish, invertebrates, and micro and macroplastics. (Photo: April Hugi)

Anna

Anna Millener excited to catch her first fish! (Photo: Carla Culpepper)

We collected water samples for nutrients, set out our camera rig to survey fishes under the canopy (the ones that got away!), and tried our hand at fishing with the sabiki rigs. Not much action with the hook-and-line fishing today, with one exception: first-time angler Anna Millender landed her first ever fish, a Bluerunner (Hardtail) right as the clock was ticking down on our fishing set. Congrats Anna! We hung around for the evening to set a pair of light traps in the Sargassummats. We collected a few juvenile fishes, including a small tuna (species to be determined), and many swarming swimming polychaetes! After wrapping up these samples, we spent a few minutes “fish gazing” along the side of the vessel, as the ship’s lights attracted a host of organisms, including some small amberjack, flyingfish big and small, squid, and other photopositive or just plain curious organisms. It was a long day, but a successful one, so we’ll sleep well tonight.

There is so much biomass in this region, we’ve decided to stay in this area, in the hopes of getting an early start tomorrow, and maybe try out a few new gear types. So stay tuned!

Sargassum

(Photo: Carla Culpepper)

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