The Winter Flounder Web



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Welcome to the Winter Flounder Spawning Habitat Study home page. 

Learn about winter flounder, what they mean to people, and why and how we study these unique fish. Use links to those pages on the left.

Below is a log of our recent activities as the study takes place. Also check the Picture Gallery for updates.

See the video clip of transmitter-tagged flounder spawning in the NMFS tank by clicking here.

Scientist's Log Book

June 2 2009

Click here to see patterns of contact for all tagged fish in 2009.

There is a separate graph for each fish. The fish tag ID appears in the legend.

Each blue point represents a detection at one of the hydrophones (vertical axis) at a point in time (horizontal axis). Keep in mind that hydrophones are crowded together (a few hundred meters apart) in the expectation that individual tag transmissions (coded pings) are heard by several hydrophones. That allows the position of the tag to be calculated by trilateration. Thus, these plots describe 2 important pieces of information:

    1) When and for how long each individual fish used the study area

    2) Which hydrophones were receiving a fish's pings in the same period. This helps narrow    our focus in pulling useful data sub sets from among the huge total set (over 18 million tag receptions among the hydrophones, including those from the beacon tags ).

Tags 2-10 are beacon tags, not fish.


April 5 2009



February 26

Following some very nasty weather days, Dave Messerschmid,  Carly Cappaluzzo, Tom Malatesta, and Tom Grothues fished for winter flounder in the hydrophone array by hook and line and caught nothing. After Grothues and Messershmid left, Malatesta and Capalluzzo trawled on the way back to the boat ramp and caught two flounder in one haul. One was a ripe female large enough to carry a sensored tag (ID 30400). The sex of the other, small flounder could not be determined so it was brought back to the lab. It turned out to be an undeveloped female.

February 17

Carly Capaluzzo, Tom Malatesta, and Tom Grothues After 10 water hauls (empty trawl nets) we caught 8 flounder in a single haul; one large ripe female (ID 57) and seven ripe suitors, one large enough for a tag (ID 61). It would seem to be a clustered distribution. In the large observation aquarium, we have seen males follow gravid females around the tank waiting for a chance. The next trawl captured two very small ripe males. Then it was back to water hauls.

February 16 2009

Tom Malatesta and Tom Grothues trawled again today and caught nothing. Fyke netter John Seminsky saw us on the water and introduced himself and crew member Roxanne. He offered us all of his flounder catch for that day and any flounder bycatch after the end of the commercial flounder open season. He was very knowledgeable and forthcoming with information and we had a productive discussion while drifting the tide. We picked four ripe males and four ripe females from his catch that were large enough to carry tags (IDs 32, 34,35, 36, 37, 30000, 30800 & 30900). We sexed and measured all the others and released them. 

February 11 2009

Tom Malatesta and Tom Grothues caught and tagged (ID 30200) the first winter flounder for this year. It was the only fish for 97 minutes of trawl net time. It was a ripe and running male, big enough to hold a temperature/pressure sensored tag.

 February 10 2009

We placed the remaining 7 hydrophones in the study site and began trawling for flounder to tag. We completed 90 minutes of net time and caught no flounder.


February 8 2008

Volunteers Dave Messerschmid and Brian Tracey, graduate student Joan Pravatiner, and  PI Tom Grothues went to the Navesink to begin installing the hydrophone array for this year’s study cycle. We had to do some serious ice breaking at the Rumson Township ramp, which we accomplish by backing the boat, still tied down on the trailer, onto the ice sheet where it broke through, pulling it back out, scooping the ice from under the trailer axel, and repeating several times. Once we have a hole big enough, we launch the boated, got in, and broke the ice around it with a shovel and some pipe anchors. Once we get the hole big enough to turn the boat around, we ran the boat up on the ice to let it crack through under its own weight until we had a channel to clear water. It took an hour. The locals were entertained. Dave was not. He thought we were going home when he first saw the ramp. 


The wind rose from 2 knots to 20 with gusts to 25. Dave, as the one of the most skilled boat operators around, gots to try to hold the boat on the GPS numbers as Brian and I kicked the heavy deep water frame anchors and hydrophones overboard. We also got a pipe anchor in place but the wind was fierce.  We began trawling for flounder to tag. We caught nothing in 30 minutes of net-time. With the heavy part done we headed for the ramp, which by now was almost ice free. A warm night should keep it that way.


April 1, 2007

Mike Holsworth of Parlin, NJ reported the recapture of a 15 inch spent female (tag 30300) originally tagged on February 1 of this year in Red Bank. He recaptured it near the Oceanic Bridge. Thanks for the report, Mike.

March 31, 2007

John Rosendale represented our research efforts with a poster at the annual Clean Ocean Action  winter flounder tournament. Lots of fish were caught in the tournament.  Most reported to have caught them near the Oceanic Bridge although someone also reported a good catch in the Shrewsbury. There were 40+ boats in the Navesink. The winning fish was 3.13 lbs with many fish over 2 lbs were weighed in.  The tourney had not seen a 3 lb fish in years.  At least several boats with 4 anglers limited out (10 fish limit per angler).  John saw 1 big female that wasn't spawned out, but heard of two more.  Most fish appeared recently spent.

Ralph Ciambruschini of Sea Bright reported the recapture of tagged flounder #17, a female of 2.1 lb  (and that's spawned out!). He said the fish was in great shape and was taken seaward of the Oceanic Bridge.

March 30, 2007

Scott Baker of Chester, New York, during a visist to the Navesink caught a flounder that we tagged last year, near the Oceanic Bridge where we had had tagged it. This female, carrying a sensor fitted tag (Tag 29700)  was almost 16 inches when we originally tagged it on February 14, 2006, and had grown an inch when Scott caught it. Thanks for the report and the image, Scott. 

Jim Shersick of Metuchen, NJ, also caught a flounder in the Navesink today  that we tagged (Tag 18) on January 22 of this year. This female was ready to go when we tagged it, and spawned out when recaptured. 

March 27, 2007

Jay Turnure and Tom Grothues trawled from the Oceanic Bridge to the Hospital in Red Bank, collecting 18 winter flounder. Most were taken just upstream of the bridge, with one in the hydrophone array and one in Red Bank, so there was a marked shift in the distribution towards the estuary mouth. We saw and spoke to anglers near the bridge who were also doing well. All of the fish we caught were spent, so we tagged none. We also collected the hydrophones. Any tagged fish still in the array should be spent as well. 

March 19, 2007

Roland Hagan, Jay Turnure and Tom Grothues trawled from east of the Oceanic Bridge to near the hospital in Red Bank using a spare net. We collected three flounders, all from within the array boundary and all spent, so we tagged none. All appear to be females, but we brought them back to the lab for microscopic examination. With four spent flounder and no ripe ones collected this week, it appears that the spawning season is winding down, although we collected spawning fish until March 30 last year. A March 31 winter flounder fishing tournament hosted by Clean Ocean Action will provide a good indication of the ratio of gravid to spent females. 

March 14, 2007

Roland Hagan and Tom Grothues replaced 7 hydrophones in the array and had time for just two trawls before returning. The first trawl collected one spent flounder just east (downstream) of the array, the second snagged something heavy anchored the boat for 10 minutes before the net finally tore, making it useless.

March  12, 2007

Roland Hagan, Arnie Fouge and Tom Grothues replaced hydrophones in position  9 and 8 with their antennas.

February 28, 2007

Ice melt from a warm rain is enough to get a boat into the water in Rumson, although lots of ice remains in Red Bank and along the shore as far seaward as the Oceanic Bridge. We find everything and recover all but one buoyed system, which is not in eminent danger.  Nothing was visibly damaged, though some of the moorings had been plowed over and sunk by moving ice sheets. None were displaced, and our GPS waypoints put us right on our toppled stakes, which we fished out with a grapple. The flexible pipe anchor design  worked well; the toppling protected the equipment from being crushed or lost. In contrast, we see that some of the shoreline residents have had their heavy piers pilings felled and their docks twisted and crushed. It will be interesting to see what the flounder were doing under all this ice.

February 15, 2007

Ice boats and off-road vehicles are running over thick ice to the western edge of the hydrophone array. We can see that several of the hydrophone antennas are standing tall through the middle of fast ice and the 2 buoyed antennas remain in open water, but several stakes are missing, presumed to be plowed over by shifting ice. Nothing to be done but wait!

February 5, 2007

It's not looking too good for further trawl efforts just now.  The antenna poles can be seen in open water but there is not much open water left.  Its completely iced up in the bay around Red Bank.  The launch ramp is iced up and there is ice along the banks near the bridge. If the ice freezes fast we may keep our gear in place, but large tidal heaves will cruch or move the shallow water antenna stakes. 

February 1, 2007

Brian Tracey (Rutgers Scarlet Knight  Line Backer # 54), a marine biology major, joined Beth Phelan, technician Jackie Toth, and Tom Grothues for a day of tagging. There were large ice floes on the river starting just above the Oceanic Bridge, but nothing  through which the boat couldn't break. Trawls came up empty until we got to the seaward edge of and into the hydrophone array, where we caught four fish, two ripe females and two ripe and running males. Having cut one tag bridle too short, we tagged only the two females and one male. The ice was gone by the evening. 

January 24, 2007

Jay, Jen and Roland tagged six more fish, 3 males and 3 females. Catches were concentrated near the hydrophone array, although trawls were made throughout the estuary. All were ripe and one very swollen female was running eggs.

January 22, 2007

We finished installation of the hydrophone array today by placing the last buoyed hydrophone and synchronizing two previously installed units. Then we trawled. We caught and tagged 7 nice fish, all ripe but none running, in 5 net hauls between the Oceanic Bridge and the eastern boundary of the hydrophone array. Having just a half hour till dark, we logged into the hydrophone that sunk last week and found it to be working fine – we watched in real time as it logged 6 beacon tags and numerous contacts with fish 13, the big female tagged two weeks ago.


January 18, 2007

Working under low gray skies with periodically thick falling snow, sleet, and freezing rain, we installed three more hydrophones before having to shut down the laptop. Thanks to Jeff Pesutti for running out some lengths of chain to properly ballast the buoyed deep-water hydrophones. We also rescued and reset a posted hydrophone that had tipped and sunk in the previous nights heavy winds, the mud being too shallow here to get a deep set. We found some really deep mud this time.

January 10 and 11, 2007

There is ice on the water. We deployed 7 of the 10 hydrophones and initialized GPS reception of 5 of them before we ran out of light and laptop battery. The potential tide range here has the hydrophone antennas towering 7 feet above the water at low tide, but only 2 feet at the very high tide. The hydrophones will remain in until April. They can be downloaded and programmed via the antenna  box without pulling them up, so we can adjustment their operation based on early results.

January 4, 2007

Jay Turnure and Roland Hagan trawled the study area and tagged 2 fish, a male and female. This early success starts the year off better than last.


December 14, 2006

We finished a dress rehearsal of the hydrophone deployment. All of the hydrophones and their antennas were staked or buoyed in Great Bay, Tuckerton NJ in similar conditions to our Navesink study area. The test location near the Rutgers University Marine Field Station allowed us easy access to the workshop while we tweaked the mooring designs. The weather on the first few days was almost too nice; the flat calm didn’t challenge us! That changed a bit today. We benefited greatly from the expertise of Gordon Carl of Applied Biometrics Inc., who came down from Canada to help us run our tests.

December 11, 2006

It is time for a dress rehearsal of the coming hydrophone deployment. This winter’s deployment will be more challenging than the previous year’s. All of the hydrophones will be clustered within an area of about a half square kilometer so that fish movement in that area is captured by multiple hydrophones at the same time. Very small differences in the time that it takes a tag signal to get to different hydrophones is used to calculate the exact position of the fish in three dimensions to a resolution of less than a meter. This process is called triangulation. It also requires a surface antenna and some shallow hydrophone placement.

 The deepest part of the Navesink River is where it is also at its most narrow, so very shallow shoreline water is also close by. By placing our hydrophones to cover this entire area, we can test the hypothesis that flounder do not discriminate between shoal and deep water during spawning activity. The preferred use of depths or shoals, especially at night and when accompanied by rising movement typical of spawning behavior, would cause the hypothesis to be rejected.


November 29-30, 2006

Tom Grothues and Beth Phelan attended the Flatfish Biology Conference in Connecticut and presented a talk with results from Year 1. We also heard from two other groups who telemetered winter flounder in New Hampshire. A common theme that we heard from other scientists is that adult winter flounder are becoming harder to find while juveniles are more common. Unfortunately, we heard of declines for other flatfish species as well. Summer flounder numbers, however, seem to be doing well.

These graphs show  which hydrophones (y- axis) detected winter flounder passage on what dates (x-axis). The further up a blue dot appears, the further a fish was upriver at that date. None of the fish went as far as the last hydrophone in Red Bank.

The graph above shows the depth at which a female winter flounder was over a period of 5 hrs around midnight based on transmissions from a pressure sensor in the tag. There is an obvious "bottom" between 2.3 and 2.5 meters, from which the fish rose into about 1 meter into the the water column at least 8 times. Each "hop" lasted 30-40 seconds - the pressure data broadcasts are 10 seconds apart. This pattern is  consistent with the behavior observed in tanks during spawning. This pattern was see for other fish at other times as well. 

April 25, 2006

Jay Turnure and Tom Grothues recovered the last hydrophone, stationed between Lower Rocky Point and Barley Point, after a quick inspection dive. The hydrophone had  been pulled up off of its base and dropped back down on the bottom nearby. This was the second time this has happened. I guess the labeled buoy attracts the wrong kind of attention, but why not just call and ask about it? Our phone number is on it.   Although the curious may  have meant no harm, the hydrophone function is compromised when it lays on its side in the mud rather than sticking up two feet above the bottom. We recovered the data and, while we could detect some passing fish, including the ones caught out in the Shrewsbury, the period of disturbance was pretty clear as the number of contacts per fish fells from the hundreds per day to ten or less.  

This brings the field phase for Year 1 to a close. Now starts data analysis and planning for the Year 2 phase, including a design for more secure moorings.

April 24, 2006

Jeff Pessutti (NMFS) kindly clipped a section  of the lengthy surveillance video from the big observation tank where we kept 2 male and 2 female tagged flounders. Spawning began within one hour of moving the fish to the tank and resulted in thousands of larval fish (see the March 21 post). Although the original high resolution had to be compromised for posting here, you will see two flounder rise up from the bottom of the tanks together in their characteristic spiral. Download the avi clip here.  

April 13, 2006

Two tagged winter flounder were recaptured this morning by anglers on the same boat as reported by Captain  Hal Hagaman of the Sea Tiger II. The boat was fishing in the Shrewsbury River, confirming that the fish had indeed left the Navesink River study area. Both fish were males. One was landed by James Darley of West New York, NJ  near lower Rocky Point where the Navesink empties into the Shrewsbury, the other a little further towards the Hook.

April 12, 2006

Data, data, data! A preliminary look at the unfiltered data (more than 60,470 contacts with tagged fish!) shows several of the flounder moving from the lower Shrewsbury up to as far as Red Bank in late March, then moving quickly back down to the area of the bridge. Several were still there as we pulled the gear, but are sure to be spent by now; others have apparently moved even lower or exited the river. Data collection from Hydrophone 1, which remains deployed in the river, will help determine this.

April 11, 2006

One of our hydrophones was pulled up and returned to us by a citizen concerned that it was in the wrong place. Another was apparently pulled up and not (yet) returned. We dove to look for it a week after noticing the buoy was missing, but the anchor and unit are gone. A trawl effort over a wider area surrounding the GPS numbers also yielded nothing except a few spent flounders. Anyone finding the lost gear is encouraged to contact us, especially since the data is still aboard the unit. 

A fishing tournament last week caught numerous spent winter flounder, but only one female with eggs. On that note, and with the apparent increasing risk to our gear, we pulled all but one remaining hydrophone and retrieved the data. Hydrophone 1 remains near Barley Point to act as a gate keeper to tagged fish leaving the Navesink. It now has a yellow ball float on it with RUTGERS and our phone number. Kindly keep an eye on it.

March 30, 2006

The tagging effort ended today after with two more ripe and running males were tagged. These were the only two fish of 11 that could be tagged; all others were small immature fish or, in one case, a large female that was already "spent" (done spawning). The flounder under observation at the NMFS lab have also completed spawning. 

The NJ DEP released an advisory regarding the consumption of winter flounder from certain areas; see it on the news page. 

March 21, 2006

The 4 acoustically tagged winter flounder in the big observation tank at the NMFS laboratory have spawned.  Larvae are visible swimming in the water column.  We are taking observations on swimming and sinking rates.  We cannot accurately estimate numbers over such a large space but we have digital video images to analyze. The fish have been under constant observation by video, so now it is time to go back and search it for the actual spawning events to see when and how often.  

March 17, 2006

After such a great catch last Monday, it was disappointing to catch only one small immature male in the trawl today. It seems unlikely that they all left, more likely they have buried themselves again during the cold snap. Downloading the hydrophone data promises to be revealing.

March 13, 2006

At last we are catching winter flounder in the trawl nets, lots of them. Technicians Gina Petruzelli and Mike Holon had captured four by 9:30 AM and as many as 15 per net haul by mid-day. Most, however, were  immature males too small to tag, but finally some females came on board. The day ended with two large egg-bound females and two ripe males tagged, and the promise of another good day later this week. So have they been here all along, buried deep and unmoving in the cold mud, or did they just make a grand entrance?

March 7, 2006

Mike Holon, Jay Turnure, and Natalie Wilkies trawled from 6:00 AM until after 10:00 AM, covering the Navesink from its headwater to and its inlet with the Shrewsbury. Caught nothing. Beginning to sound familiar?

 March 3, 2006

Mike and Jay again try their luck with Morgan at the fyke nets.  We were able to pick up tag one female out of one of his nets.  Afterwards, we headed over to the NMFS lab at Sandy Hook to tag flounder from a captive stock for tank studies of spawning behavior.  We tagged two females to even the ratio with previously tagged males in the lab.  The four lab fish were released into the large tank together with untagged and dummy-tagged fish to see if tags interfere with spawning behavior. 

 February 23, 2006

This week we combined efforts both fyke netting and both day and night trawling. To even the male to female ratio, we are tagging only females.  We worked with Morgan Kavanaugh and his fyke nets with little success, catching only a few small males. In addition, we trawled both day and night. Both attempts were fruitless. On Tuesday with the help of John Rosendale of NMFS we were able to trawl a large area of the river covering all possible habitats, muddy and sandy bottoms, channels and flats.  On Thursday, Mike Holon, Jay Turnure, and Tom Grothues, armed with a chum pot and trawl hitting the water at 9:00 PM.  After 6 unproductive hours on the moonless Navasink, bracketing the dead low tide at 11:55 PM, the crew called it a night and returned home at 4:30 AM. We caught a herring.

February 14 and 15, 2006

Morgan Kavanaugh and I tagged 2 female flounders and 3 males captured by fyke net in the lower Navesink. We delivered 7 additional males to the NMFS lab to test their willingness to spawn with dummy tags. The sex ratio remains skewed, suggesting that spawning is just beginning. The males were running ripe and the females were swollen with eggs (below and Gallery). 

The swollen "side" is actually the ventral or belly side, with egg laden overies extending towards the tail. The thin edge is the fish's back. She is laying on her left or "blind" side, and both eyes are on her right side.

February 5, 2006

Fyke netters Dennis and Morgan Kavanaugh donated seven winter flounder captured in their gear over the last two days. Four were large enough to tag. These were all males and  "running ripe", meaning that they are leaking milt when handled. Males of many fish species typically arrive on spawning grounds first. The females, when they arrive, will be larger. We tagged the four fish in the nearby NMFS lab at Sandy Hook and moved them to a pool for observation before release. They were very docile when handled and tolerated tagging extremely well. They swim normally in the tank with untagged smaller flounder. One will be released into a giant observation tank for a while before release where it can bury itself deeply if it wishes; untagged flounder may bury to six inches. This will allow us to test detection of buried tags, which is expected to dampen transmission. 

January 27, 2006

Three more hours of trawling and no fish. At the ramp we meet commercial fyke netters that also bemoan the current scarcity, but promise to help us if they do catch any winter flounder in their gear. Not to worry yet, historically this is just the beginning of the spawning season in the Navesink.

January 24, 2006

Three and a half hours of trawling, sweeping almost eight linear kilometers in shallow and deep water, from the mouth of the Navesink to its headwaters, nets no winter flounder. NMFS' John Manderson reports sighting a single one for several hours of video sled trawling in the same area. Water is still a relatively warm 40 oF; so spawning could be delayed this year.

January 20, 2006

Deuce, Jay Turnure, and Tom program hydrophone duty schedules to 40 sec awake, 80 sec  asleep, and deploy them during the falling tide. Float lines for 1 and 4 only show on mid-low tide.

January 13, 2006

Tags and hydrophones arrived last week. Technician Michael “Deuce” Greaney helped assemble, power up, and program the units for duty using a laptop connection. Technicians Mike Holon and Deuce help Tom Grothues deploy nine of the pipe anchors on a calm but foggy day during a minus tide (see the Gallery page). Meanwhile, co-investigator Beth Phelan and her NMFS associates pull a camera sled across the study area looking for winter flounder and reading light levels to program aquarium lights for tank testing the tags on fish. The freezing cold weather of mid December was followed by two weeks of warm weather and the water is a balmy 41o F. Not surprisingly, the camera sled finds no flounder moving up the river.

December 22, 2005

The problem with winter flounder is that they like it cold. We should have studied groupers. Aside from being uncomfortable, ice is tough on gear. It can drag floats and gear, or tear the floats away from the gear. Here is our solution: Pipes are sunk into the mud with just enough sticking out to fasten the hydrophone. A line from the pipe goes to a small bullet-shaped float (like for crab pots) using floating polypropylene line. 

December 14, 2005

Together with Shah Muossavi of Applied Biometrics Inc. and Navesink locals John Manderson and Jeff Pessuti of NMFS, we surveyed the study area for sound properties on Tuesday, 12/13. It was cold. Hand and toe warmers barely took the edge off. We powered the boat slowly through 2-inch thick ice off Red Bank (pictured in gallery). Shah characterized ambient noise (possible interference) in the turbulent tidal rip off Lower Rocky Point. Between the Oceanic Bridge and Red Bank, we  measured the distance from which we could detect and decipher three coded tags moored in the water as we backed away in the boat. This information helps finalize positioning of the listening gear (hydrophones), which need to stay submerged under the ice.

October 6, 2005

Presentation of proposed work at the DOT Dredging Summit at Monmouth University in Long Branch, NJ. Click here to download Powerpoint slide show: Understanding and Resolving Conflicts Between Winter Flounder and Dredging 

October 3, 2005

Funding is awarded from the I Boat New Jersey program of the Department of Transportation


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