Storms and strong currents end Slope Sea operations

The Slope Sea portion of this cruise ended a little early due to storms and strong currents, but will provide important information on this poorly understood region of the ocean.  We did not complete our entire planned cruise track for the Slope Sea, but we did complete 84 stations in the northeast for a total of 133 bongo and CTD tows and 13 water casts.  The bongos will be used for our plankton analyses, including our hunt for bluefin tuna larvae.

Plankton sampling continued to catch scombrid larvae, including a few more potential bluefin larvae. We never hit a large enough patch to justify releasing drifters. We will save the drifters for another cruise that leaves in two weeks for the Slope Sea.  The water samples from the water casts will be sent off for dissolved inorganic carbon (DIC) and total alkalinity analyses. Both DIC and total alkalinity are used by chemical oceanographers to estimate pH of the water, and examine current ocean acidification conditions of the ecosystem. The basic hydrographic data collected (temperature and salinity by depth) will be used to define ocean features in the Slope Sea and to help ground truth satellite data.

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Picture of a recently caught 8-mm long little tunny (Euthynnus alletteratus) larvae.  Larval scombrids eat other larval fish, as seen by the larvae in the stomach of the little tunny / bonito.  Photo credit: Ciara Willis, Dalhousie University

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Ciara (front) and Chris (middle) wash down the bongo nets as ENS Fuller (back) prepares for a water cast.  Photo credit: Harvey Walsh, NOAA/NEFSC.

Weather and sea conditions required an adjustment to our planned cruise track, moving inshore one evening when winds and seas along the Gulf Stream made bongo sampling difficult.  We normally send the bongo down to 200 meters deep ( about 660 feet), and use about 280 to 300-meters of wire, and still could not get the net to that depth.  On the final tow of the evening, we deployed over 400 meters of wire and still could not get the net below a depth of 150 meters ( about 480 feet).

Like flying a kite on a breezy day, the current was pushing the net up with too much force or lift to overcome with our standard weight.  The ship’s bridge and crew were safely able to deploy and tow the gear, but the sea conditions wouldn’t allow for us to collect samples that we could compare to all the others we had collected. After we moved inshore to escape the strong current, we continued to see a highly diverse plankton community in the waters just offshore of our standard sampling locations during EcoMon.

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Plankton collected in a bongo sample about 30 miles north of Cape Hatteras, North Carolina.  The sample had squid paralarvae and fish larvae including: common dolphinfish (Coryphaena hippurus), shoal / dusky flounder (Syacium spp.), and unidentified gobies (Gobiidae).  Photo credit: Ciara Willis, Dalhousie University

Even though we moved inshore, we could not escape the thunderstorms that were moving through the area. We had suspended operations at a station just north of Cape Hatteras due to lightning in the area. Have you ever wondered if lightning strikes the ocean? A few minutes after we arrived at the inshore station there was a very close strike, or the ship was struck by lightning ( it depends on who you ask).  Everyone on board was safe, but we lost gyros and some other electronics.  We steamed on to the next station, the second to last scheduled for the northeast part of the cruise, as the ship’s Electronics Technician (ET) began repairing systems.  We discovered that the CTD would not talk to the computer when we resumed operations at the next station. Wherever the lightning hit, our science gear did not escape the damage.

We decided to move down to the southeast shelf, south of Cape Hatteras, North Carolina, to escape the marginal weather, and the unknown amount of time it would take to diagnose and fix the CTD problem.  Thankfully, the CTD was repaired on the transit south thanks to the persistence and skill of Betsy Broughton (NEFSC scientist) and Kirk Andreopoulos (ET on the Gordon Gunter).  We will continue to explore poorly understood parts of the western Atlantic during the second half of this cruise, this time in the waters off the southeast United States coast.

Check back on to read about what and why we are studying the ocean south of Cape Hatteras, North Carolina.

Harvey Walsh
Chief Scientist
NOAA Ship Gordon Gunter  GU 1702

Plankton Ops

The plankton sampling team for this cruise is made up of six researchers from NOAA Fisheries and regional universities.  Each 12-hour watch has a team of three people, so that we can sample day and night.  Betsy Broughton (NOAA Fisheries/NEFSC), Christine Hernandez (Woods Hole Oceanographic Institution [WHOI]), and Quentin Nichols (NOAA Fisheries/NEFSC summer intern, UMass Amherst) staff the night watch, 3-pm to 3-am.  Ciara Willis (WHOI summer intern, Dalhousie University), Chris Gingrich (NOAA Fisheries/NEFSC summer intern, Washington College) and I stand the morning watch, 3-am to 3-pm.

There are still a lot of questions about this area as a spawning ground for Atlantic Bluefin tuna.  One of the research questions being addressed on this cruise is how the currents of the Slope Sea affect the planktonic larval stage of bluefin tuna.  Plankton are organisms that rely on the wind and ocean currents to move through the ocean (from the tiny algae and small amphipods to larval fish and crustaceans to jellyfish). We are hoping to find patches of larval bluefin tuna where we can release drifters that will track the movements of the water surrounding the larvae as they grow.

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Christine Hernandez (front) and Ciara Willis (back) sort samples in the lab as the samples are brought on board.  They also take pictures of larvae for us to post (see images below).

At each station, we sort a small portion of the sample we just collected for any fish larvae we can find.  The larvae we’re looking for are tiny, 2-10mm (about 1/16 – 3/8 of an inch) long, so we need to use microscopes. We also have to work fast, so we don’t drift too far from where the larvae were caught. We have found one potential Bluefin larvae already, which we will verify with DNA analysis.  We are hoping to find a larger patch to justify releasing the drifters.  We’ve also seen plenty of cousins of Bluefin including bullet or frigate mackerel (Auxis spp.).

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Picture of a fresh caught larval bullet / frigate mackerel.  These are small cousins of the bluefin that are found in surface waters of the open ocean.

The influence of the warm Gulf Stream waters can be seen in the diversity of the fish community caught in the bongo nets.  In addition to the tuna and mackerels, we are catching more tropical and subtropical species like driftfishes (family Nomeidae) and eyed flounder (Bothus spp.).

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Larval (top) and juvenile (bottom) driftfish caught in the bongo nets.  Driftfishes are open ocean (pelagic) species, often associated with drifting algae like sargassum or jellyfish, particularly as juveniles. Photos of fishes by Christine Hernandez and Ciara Willis.

Harvey Walsh
Chief Scientist
NOAA Ship Gordon Gunter, GU1702

Seeing some interesting seabirds, marine mammals and sea turtles

Over the past six days, observers Timothy White and Glen Davis have been working together from sunrise to sunset to collect abundance and distribution data of seabirds, marine mammals and sea turtles from the Gunter’s flying bridge. This project is an extension of the Atlantic Marine Assessment Program for Protected Species (AMAPPS), which is an ongoing partnership between BOEM and NOAA. Timothy and Glen report high diversity and abundance in transitional waters and zones characterized by steep temperature and salinity gradients.

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Observers Timothy White (right) and Glen Davis (left) at work on the flying bridge.

The following species list is rapidly growing and includes unique seabirds not often observed on the shelf:  Trinidade Petrel, White-tailed Tropicbird, Black-capped Petrel, Brown Booby, South Polar Skua, Manx Shearwater, Arctic and Common Terns, Pomarine Jaeger, Band-rumped Storm-Petrel, Audubon’s Shearwater, Leach’s and Wilson’s Storm-Petrel, and Cory’s and Great Shearwaters — the last four are notably migrating to the north widely through the area.

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Numerous Great (left) and Cory’s Shearwaters (right) have been observed migrating north over Gulf Stream waters.  Great Shearwaters breed on sub-Antarctic islands. Cory’s Shearwaters breed in warmer waters on islands in the eastern Atlantic.  Both species are abundant on Georges Bank in summer where they feed on fish. Photo by Glen Davis.

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Endangered black-capped petrels (white-faced morph pictured) were observed on multiple days over well-mixed waters. Photo by Glen Davis.

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A 1st year Brown Booby from the Caribbean. Photo by Glen Davis.

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Band-rumped storm petrels originate on islands in the eastern Atlantic and are abundant in the Gulf Stream. Photo by Glen Davis.

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A 1st year Pomarine Jaeger molting feathers.  This bird was born in the Arctic. At sea, Pomarine Jaegers are kleptoparasitic, which means they pirate food from other seabirds.Photo by Glen Davis.

As of June 15, marine mammals sightings include: Sperm Whales, Killer Whales, Striped, Atlantic Spotted, and Bottlenose Dolphins. Loggerhead Sea Turtles have also been observed.

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These striped dolphins were members of a large pod that consisted of ~ 200 individuals. Photo by Glen Davis.

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A loggerhead sea turtle in warm, blue Gulf Stream water. Photo by Glen Davis.

Tim White
Aboard the NOAA Ship Gordon Gunter, GU1702

Searching for Atlantic bluefin tuna larvae and more in the Slope Sea

The NOAA Vessel Gordon Gunter departed on June 10 from Newport, Rhode Island, and immediately headed off the continental shelf to water deeper than 1,000 meters (about 3,300 feet) known as the Slope Sea.  The Slope Sea is an area of the ocean that is bounded to the north and west by the northeast United States Continental Shelf and to the south by the Gulf Stream, whose dynamic currents provide a strong influence over the area.  The Gulf Stream is constantly shifting position and pathways, like a giant water snake slithering through the ocean, and will frequently shed pockets of warm water, called Warm Core Rings, into the Slope Sea.  The dynamic nature of the Gulf Stream creates a mosaic of habitats that are used by a wide range of species.  However, very little of the Slope Sea has been explored, and little is known about who calls it home.

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Sea surface temperature image from NOAA-19 satellite for the Slope Sea blue fin tuna cruise the day of departure.  The water temperature is shown in the colors, with blue cold temperatures and red warm.  The Gulf Stream shows up as the darkest red.  The black line represents the proposed cruise track for the northeast portion of the cruise.

The cruise now underway is targeting a different set of objectives from the standard Ecosystem Monitoring (EcoMon) cruises run by the Northeast Fisheries Science Center (NEFSC)’s Oceans and Climate Branch.  As described in a previous post, the EcoMon cruises are designed to monitor lower trophic levels, oceanographic conditions, and the distribution of fish larvae and eggs across a wide area of the continental shelf.  While some changes have been made over time, this area has been sampled with the same general sampling approach since the 1970s.

The current cruise stands in sharp contrast to the EcoMon program in that it is focused on a rarely sampled area, the Slope Sea, and much more prominently on a single species, Atlantic bluefin tuna.

Atlantic bluefin tuna are one of the iconic marine fish species.  Over the course of their seasonal migrations, individual bluefin tuna can occupy both nearshore and oceanic waters, swim across the ocean, and cross through international waters and the exclusive economic zones of multiple nations.  These migrations expose bluefin tuna to a wide variety of fisheries, a factor that presents a notable challenge to managing this species.

In recent decades, the common view of Atlantic bluefin tuna was that they spawned only in two places, the Mediterranean Sea in the Eastern Atlantic and the Gulf of Mexico in the western Atlantic.  However, in the summer of 2013 two cruises sampled the Slope Sea, both of them achieving noteworthy catch rates of early-stage bluefin tuna larvae.  These collections were consistent with a hypothesis first put forward in the 1950s that the Slope Sea was a third spawning ground for this species.  Follow up sampling in 2016 again achieved notable catch rates of bluefin tuna larvae.

Researchers aboard the NOAA Ship Gunter are evaluating the distribution and abundance of bluefin tuna larvae in the Slope Sea spawning ground.  This cruise is sampling earlier in the season than previous Slope Sea cruises to provide us information on the regional start of the spawning season for this species.

The scientists aboard also include two sea bird observers who will be conducting visual observations during the daytime transits between stations.  In addition to sea birds, they will be looking for whales and dolphins, sea turtles, large fish, and jellyfish.

While the focus of this cruise is on Atlantic bluefin tuna, one other exciting aspect of the project is that we are not certain of the full suite of other species we might collect or observe during visual surveys.  The Slope Sea has long been hypothesized to be important in the life history of other species, besides Atlantic bluefin tuna, that support economically valuable fisheries off the northeast United States.  Given the limited sampling that has been done in this region, it is quite possible that a new discovery will result from this cruise.  Follow along  for the next 2 weeks, as we travel through the Slope Sea and down the United States Atlantic coast to Cape Canaveral, Florida, as we further describe our mission and our initial discoveries.

Scientists and Crew of the NOAA Ship Gordon Gunter, GU1702
Harvey Walsh, Chief Scientist

Why do we do the EcoMon surveys?

May 25, 2017

The Gordon Gunter is just finishing up Leg 1 of the Spring Ecosystem Monitoring Survey.  By tonight we will have completed sampling at ninety-two stations, encompassing  all of the Mid-Atlantic Bight and Southern New England areas.  We were very lucky in that the low pressure system that threatened to make conditions unworkable on Georges Bank dissipated and we were able to reach some stations on its southwest corner, thus freeing up Leg 2 to concentrate more on the rest of Georges and the Gulf of Maine.  After docking at Naval Station Newport on Friday morning, the Gunter will be in for the weekend and then pick up a partially new scientific complement on Monday, Memorial Day, and sail that afternoon.
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A loggerhead turtle photographed on day 5 of the cruise. Photo by John Loch, Integrated Statistics

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A pod of common dolphins, also photographed on day 5 of the cruise, by John Loch, Integrated Statistics.

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Banana dolphins created by Paul Acob, second cook aboard the  Gordon Gunter. Photo by Jerry Prezioso, NEFSC

While out here I received an email asking why we are doing this work out here.  I’ve given a lot of thought to how we do our research, but not so much about the why.  It’s a fair question. Maybe in these times of discussion about how much and how fast our climate is really changing and how much is caused by man, this becomes a question that we should be readily prepared to answer.
My answer would be that we need to do these ecosystem monitoring surveys because we are on the front lines of observing and documenting first hand what’s going on in our coastal and offshore waters.  The science staff, aided by the ship’s command and crew, is working 24 / 7 to document as much as they can about the water conditions, not just on the surface but down to 500 meters, by measuring light, chlorophyll, and oxygen levels as well as nutrients available.  Water column temperatures and salinities are profiled and Dissolved Inorganic Carbon (DIC) levels are checked as a way of measuring seawater acidity at the surface, mid-water and bottom depths. What planktonic organisms are present?  Plankton tows across the continental shelf down to 200 meters are made to collect them.  What large marine organisms such as whales, turtles and seabirds are present in different areas and at different times of the year, and are they different from one year to the next?  From one decade to the next? Two seabird observers work throughout the daylight hours to document and photograph large marine organisms encountered along our cruise track.  Without this information being gathered on a regular basis and in a consistent manner over a long period of time, we would have no way of knowing if things are changing at all.
So that’s my answer.  I want to point out that it is really a team effort to collect all these data and samples.  I want to thank the ship’s crew and command for making this cruise a real success, even when we didn’t get the typically benign May weather I had been expecting!  The command was checking our potential cruise track constantly to take weather set-backs into account and keep us working at maximum capacity, even when we were slowed down due to seas and winds.
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Suffolk Community College student Maira Gomes on her first research cruise rinsing a plankton sample from the “baby” bongo net. Photo by Jerry Prezioso, NEFSC

The crew kept the ship running smoothly with not a minute lost to any mechanical problems, and deployed the bongo nets and CTD-rosette safely and efficiently even when conditions were less than ideal.  We couldn’t ask for better accommodations or food.  Every meal offered a variety of entrees to satisfy a variety of tastes.  And the science staff did a super job, with veteran sea-goers training newly arrived students, one of them at sea for the first time ever, to fit in and take up their tasks of collecting data and samples from the ninety-two stations that were completed during this leg.
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CTD specialist Tama Holzwarth-Davis processing data from a just-completed bongo net deployment as the “mission control center” in the dry lab of the Gordon Gunter. Photo by Jerry Prezioso, NEFSC

Thank you all for making this trip such a success. I’ve had the pleasure of sailing with many of you in the past, and I hope to do so again!
Jerry Prezioso
Chief Scientist
Spring Ecosystem Monitoring Survey GU1701

Salmon team and predators ready for Spring on the Penobscot

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This is the computer readout from our two frequency echosounders.  The water surface and bottom are thick red lines, the specks in between the lines are likely fish. Photo by NOAA/NEFSC/NEST

Another beautiful spring day in Maine means that salmon biologists are busy in the field.  Since our last post, we’ve been waiting for the warmth of spring to arrive, bringing with it the sea-run fish migrations.  Last Friday we conducted one of our biweekly fish surveys of the Penobscot Estuary.  We used single frequency echosounders, also known as “fish finders”, to measure the amount of fish in the water column as we cruised through the estuary.  Generally this technique is called “hydroacoustics,”and uses sound waves to record what types of objects are in the water.  In our case we are using it to identify fish in the water.

For the past five years, we have made the same cruise along the Penobscot Estuary and are accumulating the data from echosounders which translate into the number of fish.  This allows us to describe patterns of fish abundance.  Many of these fish are sea-run species that make a migration inland during the spring.

Why is this important? Because one aspect of our research is understanding the dynamics of Atlantic salmon smolt survival as they migrate from rivers to the ocean.  Previous studies have shown that predators are a big factor. This survey is designed to figure out where predators such as large fish, cormorants, and seals congregate relative to their prey – namely, fish.  While the echosounders are counting fish, we observe the birds or mammals that we see, record their species, number, and behavior (feeding or resting).  Describing the overlapping distributions of predators and prey is the first step in understanding the complex ecological interactions that salmon are part of as they migrate to sea.

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A pair of loons looking for a meal in the freshwater portion of the Penobscot River estuary. Photo by NOAA/NEFSC/NEST

 

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A harbor seal sits on a haul-out ledge. The Penobscot Estuary survey records the number and location of any marine mammals encountered to help in determining areas of potentially high predation for Atlantic salmon smolts as they migrate the estuary. Photo by NOAA/NEFSC/NEST

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Roosting double crested cormorants. These birds are exceptional fishers that eat migrating Atlantic salmon smolts in Maine Rivers.  Photo by NOAA/NEFSC/NEST

In this survey our nice day turn unsettled when Northwest winds instigated a small craft advisory for the area.  Luckily for us we were already north of the more exposed areas of the survey and could safely continue on our mission.  We saw a number of cormorants and seals but they were mostly at roosting and haul-out areas.

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Justin Stevens, contract NOAA Fisheries biologist, navigating the Penobscot Estuary during a fish survey using hydroacoustics. The weather looks nice but mid-survey a small craft advisory was issued for the general area and this is the face of a boat operator scowling at the news.

 

The number of fish counted with the echosounder was less than we have seen in previous years by this time, but water temperatures are still around 10°C (50°F) so we probably are not close to the peak of the fish migration.  My gut tells me that things will be changing soon given we have started to have some sunny days with temperatures in the 80s.  One thing that is guaranteed, things will be different next time we are out.

 

The NOAA Fisheries Northeast Salmon Team

Penobscot River, Maine

 

 

 

 

Sea Angels, OASIS and Terns

May 22
As I am writing this the Gordon Gunter is heading for its sixty-third station about ninety miles south of Martha’s Vineyard.  This station is just off the shelf edge as we work our way east along the offshore part of the Southern New England area of our survey.  Our intent to is reach and sample the southwest corner of Georges Bank in the time we have left before returning to Newport, Rhode Island on Friday morning.  Yesterday this seemed like a daunting task, given a rather dire forecast for Wednesday on Georges Bank, but with the stalling of a frontal system that forecast now looks like it will be delayed long enough for us to continue working offshore and return to more sheltered inshore waters by the end of our scheduled sailing time.
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Biologist Chris Taylor guides the bongo net array onto the Gordon Gunter‘s deck.  
                Photo by Jerry Prezioso, NEFSC

Most of these stations have been sampled with bongo-style plankton nets, but eleven have made use of our CTD 911 and Niskin bottle rosette array, to gather water samples from various depths,as well as profiling temperatures, salinities, chlorophyll-a, oxygen and light levels through the water column.
All the gear has been working flawlessly, as well as the Oceanographic At Sea Information System (OASIS) software that is running it, in its first trial at sea.  Thank you Joan Palmer and John O’Neil from NEFSC’s Data Management Services for your support on this!  Also Maureen Taylor and Tamara Holzwarth-Davis of NEFSC for their collaborative efforts to make it work, and who are sailing with us right now to monitor its performance while performing their other sample and data collection tasks.
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Stony Brook University graduate student Lis Henderson filtering sea water drawn from one of                 the Niskin bottles directly in front of her.  Photo by Jerry Prezioso, NEFSC

Most of our plankton catches have been fairly “clean”, unencumbered by large amounts of phytoplankton or gelatinous organisms, although our very last tow, in deep water near the shelf edge, did have a fairly large amount of phytoplankton.  Most of the tows have been dominated by small copepods and a few stations had some hyperiid amphipods in them.  We have also been seeing a few “sea angel” pteropods in some of the plankton samples, although by the time we wash them out of our plankton nets, their colors are a pale remnant of what they look like in the water.
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Sea angel pteropod (a shell-less planktonic snail) caught in one of the bongo nets.
                 Photo by Lis Henderson, Stony Brook University

On a larger scale, our bird and marine mammal observers, John Loch and Nick Metheny, have made a variety of observations, ranging from right whales at the very beginning of the trip, to loggerhead turtles, common dolphins, shearwaters and common terns over the past few days, while today they spotted several basking sharks.
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John Loch and Nick Metheny scouting for marine mammals and seabirds from the                 flying bridge of the Gordon Gunter.  Photo by Jerry Prezioso, NEFSC

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One of the many common terns seen during Leg 1 of  the Gordon Gunter EcoMon cruise.   Photo by Nick Metheny, Integrated Statistics

We made excellent progress on our way south towards Cape Hatteras, but were slowed down quite a bit on our way back north by higher than forecast winds. Conditions have now improved and the vessel is back up to full speed in transiting between stations.  The crew and command have things running pretty smoothly, and if these conditions hold, they should be able to get us through the southwest corner of Georges and back to Narragansett Bay by Friday morning!
Jerry Prezioso
Chief Scientist
Spring Ecosystem Monitoring Survey, GU1701