Sheepshead Tagging Research, Lewis Naisbett-Jones (UNC/IMS)
We’ve had on this show many times research being done with fish particularly focusing on tagging studies, speckled trout, gray trout, cobia and this one has to do with tagging sheepshead. Good morning Lewis. Before we get into the study itself what are some of the things that we DO know about sheepshead, then we can figure out what we need to learn.
LNJ (10:07): I think the inshore aspects of sheepshead behavior is really well studied. When they are accessible in the summertime, when they are inshore and around peoples’ docks and various other habitats we know a lot about that part of their life history. We know that the juveniles prefer sea grass, shallow water kind of a vegetive habitat.
Before they go to the hard stuff.
LNJ (10:36): Exactly, they grow as adults and that’s when you find them near the wrecks, reefs and rocks, we know a lot about that in particular.
What do the juveniles feed on?
LNJ (10:47): Lots of small crustaceans, they are not super picky they will eat kind of whatever they can get a hold of in the sea grass habitat.
So where are we going from there? So what are some of the questions, if you start a tagging study you obviously start off with some kind of idea of what questions you want to try to answer? What’s your list of questions?
LNJ (11:08): So really there are two main areas that we are interested in, in our study and it’s all centered around the offshore aspect of sheepshead behavior. So we want to know where do they go when they leave inshore areas…so where do they spend their winter times. And more importantly where do they go to spawn. So where do they reproduce.
So how are we going to do that?
LNJ (11:38): Well, they are a hard species to study because they are hard to catch as I know that many people are aware.
People that catch them, it’s sort of like flounder, it’s the people that target them, you don’t get a lot of people that catch them that aren’t targeting them.
LNJ (11:55): Exactly, when you first get into sheepshead fishing it’s a very frustrating sport, but you soon pick-up little tricks along the way that helps with that process. So we’re interested in that offshore component where they go and we are getting at that by using a series of different tracking methods. We are using three different types of tags to track the movements of the sheepshead.
And what are those three alternatives?
LNJ (12:30): So we’re using conventional spaghetti tags, which are just these little plastic numbered tags the same ones everyone uses, the red and the yellow tags, and they are out there with a contact number for me and if any anglers catch a fish that we’ve released with these tags, there is a reward. We work with local fishing shops like Chasin’ Tails and Neuse and we give out gift certificates if the information is returned from those fish. We also use a type of tag called an acoustic tag, which is implanted inside of the fish which sends out little pings of sound. And we have underwater hydrophones so these kind…hear and identify the pings.
How many hydrophones are out there, because obviously these are used for a number of different studies? They are shared.
LNJ (13:16): I don’t know they exact number but probably somewhere between 50 and 100. There is a good number out there and all the different research groups kind of work together on this. So we have a number, NC State has a number of those receivers out there so we kind of share that data which is really nice.
MM: How much time do you have with the fish when you are tagging it?
LNJ (13:39): It’s pretty short, so we’ll get it on the boat and we’ll try to do for the acoustic tags surgeries, we try to do them within 10-minutes. The fish is under anesthesia it’s on a table on the boat. It’s a hard situation to do surgery because the platform is moving, but we aim for 10-minutes and the quicker you can do it the less stress is caused for the fish and the higher likelihood they’re going to swim off happy and healthy.
The trickier one is the archival PSAT tag. What are they and we’ve seen them on sharks and others, but they are awfully big.
LNJ (14:17): Yes, in my opinion this is the coolest aspect of our study. These are “besasolite” tags, this is a special type of satellite tag that we’re using and it’s called a pop-off satellite tag or PSAT. What that means is that we attach these large satellite tags to the fish and we program them to detach or pop-off from the fish after a certain period of time. And the way people will put these on sea turtles and things like that, they work quite well because the antenna is always at the surface and so they can communicate with the satellite but with a fish you can’t do that because they are deep underwater for a large part of their time. And so these tags store data as the fish are moving and when they surface, on the day that we program it to do that, that’s when the antenna communicated with the satellite and sends us all that stored data. But you’re right, these are really large tags…
And the sheepshead aren’t…
LNJ (15:17): And the sheepshead are not! No, historically they have been used on sharks, tuna and billfish and cobia and fish like that. So we are really pushing the limits of the size of the fish that can carry these tags. And what’s helped is they have reduced in size slightly within the last 10-years so that the tags that we are using are maybe 30-percent smaller than the original satellite tags that came onto the market. But it’s still a big tag for a small fish.
MM: How big is the tag?
LNJ (15:51): It’s 40 grams, about one and a half ounces, but it’s 4.5-5-inches long and that doesn’t include the antenna, so when you have the antenna it’s almost half the length of the fish but the antenna is pretty low profile.
You’re putting these on the bigger fish that you are catching.
LNJ (16:13): Exactly, so we target largest sheepshead we can get.
How do you catch your fish?
LNJ (16:20): Hook and line! We do work a little bit with pound net fishermen, but because of the restrictions to the flounder season it’s been harder to get sheepshead from them and they are typically a by-catch of the flounder pound nets. So a lot of the fish that we have tagged over the last two years all been caught by hook and line.
What’s your favorite bait?
LNJ (16:41): Great question. So we’ve gone through different baits over the last two years. I think my personal…if I had to choose just one bait I would probably stick to mud crabs or fiddler crabs. We’ve also had great success with sea urchins and mussels as well.
In the different groups of fish you’ve tagged how many fish have you tagged with the spaghetti tags, the acoustic and the satellite tags?
LNJ (17:10): So we’ve done just over 600 fish with the spaghetti tags, at two years, a lots of days fishing on the boat fishing for sheepshead. We’ve done approximately 50 fish with the acoustic tags and again another 50 with the satellite tags.
Are you getting good returns?
LNJ (17:26): Well yes, for the spaghetti tags we’ve had about 68 anglers call in fish that they’re recaptured in the last year or so, which has been really valuable information. And we’ve been getting good detections from our acoustic tags and a good success rate from our initial deployment of the satellite tags.
From the acoustic tags you know daily where the fish are, what they are doing, where they are hanging out, where they are feeding where they are wandering on a general basis. Do they move around very much?
LNJ (18:01): They do. It’s hard to say for sure because a large part of it relates how much coverage you have with the (hydrophone) receivers, and we don’t have them everywhere but we do have good coverage inshore and especially around the Morehead City area. So we do have good data that suggest that at least a small number of sheepshead, the mature adults, actually remain inshore within the inlets year round. Obviously another proportion of that population does leave and migrate offshore to spawn as well. It’s been very interesting data to look at.
Whatcha got Lewis , what do you know so far?
LNJ (19:22): We’re halfway through the study so the data is still kind of rolling in. But our early findings have been really interesting. We’ve identified a number of adult sheepshead leaving the inlets to migrate offshore and that started late October and continued right up into early December we had detections of fish leaving and making their way offshore. Satellite tagging data from our first year of our project identified a bunch of locations, most of them relatively close to the inlets.
LNJ (19:56): Like within five miles of the inlet for the most part. Fish hanging around artificial reefs AR-315 and some of the live bottom areas close to Beaufort Inlet.
So you’re guessing that those are possibly the spawning grounds for those fish, or where do you think that’s occurring?
LNJ (20:16): Yes, I would love to say where the spawning grounds are, but it’s a little too early to say but certainly these locations that we’re getting are within the window that we anticipate the fish are spawning so that spawning grounds probably are within these areas or very close to these areas.
What time of year?
LNJ (20:36): April is the time when our tags pop-off and give us the locations of the fish, and we think spawning/reproduction is April/May time.
That’s just before they start to come back in then.
LNJ (20:47): Exactly.
We start seeing them staging just outside the inlets early spring and April they start coming back to the piers and inside.
LNJ (20:58): Exactly. We did have one fish with a tag which came off slightly earlier in December and that fish was about 22-miles south off the coast from Beaufort Inlet.
Where do you go from here?
LNJ (21:11): We have to wait for April until we get the tags to pop-off. It’s a waiting game here, but it will be really interesting to compare this year’s data to last year’s data and see if there is a common pattern between years.
Do you get a feel that these fish survive pretty well? When they did the studies with the gray trout they lost a lot of trout. These are pretty good surviving and coming back and forth?
LNJ (21:39): Oh yes, we realized pretty early on that sheepshead are really hardy fish, especially compared to gray trout and some other species. So we have really high survival rates post-surgery and post tagging procedures. And a fact that a large number or our tags made it to April suggest that those fish were alive and well.
Can we get you back next spring??
LNJ (22:09): Yah! Love to.