Dogfish!

Squalus acanthias

Squalus acanthias, or the Spiny Dogfish, is a species very important to our gill net research.  Despite the name, Dogfish are a species of small shark that are commonly found between 50-149 m, but have been observed venturing below depths of 700m.  This species has a venomous spine in front of each dorsal fin, thus the term "spiny."  The fishermen we work with use gill nets to catch these fish, which they then sell sell to a growing regional and overseas market.  In Europe, Dogfish is often served as fish & chips.


Dogfish are a migratory species.  They spend the winters in offshore southern waters, and move north for the summer months. Despite their relatively small size (3-4 ft),  Dogfish are aggressive and are commonly observed relentlessly pursuing prey.  The name "Dogfish" arose from the species' habit to hunt in packs.  Groups of hundreds or thousands sweep through an area and feed on the fish, crabs, shrimp, squid, and other invertebrates in front of them.  

Spiny Dogfish are believed to have the longest gestation period of any vertebrate, 20-22 months.  This coupled with the fact individuals don't reach sexual maturity until they are ~20 years old, creates a precarious situation if the species is overfished.  The long gestation and high age-at-maturity means if the population declines significantly, it will be hard to bring numbers back.  Luckily, stocks have been managed since the 80's, and the species is being fished responsibly.

Me holding a Spiny Dogfish caught in 2016

Thanks for reading, and stay tuned for more info!

New Hampshire Raised Gill Net Results 6/27

Hi Everyone!


This past week I went fishing on the F/V Marion J, whose crew were using our experimental gill nets in their quest to catch Dogfish.  Although we only hauled 2 strings containing 2 experimental nets, the results looked promising.

First, for those of you who do not know how gill netting works, here is a quick breakdown.  Fishermen string together nets like the ones shown to the right, approximately 11 nets long.  They set the nets on the bottom in this case, and let them soak for 24-48 hours.  The fish can't see the nets and swim headfirst into them where they are entagled.   Then, the crew comes along and hauls the nets, picks the fish, and re-sets the net.  Pictures are worth a thousand words, so here are pictures (and videos) showing those processes.

Part of the machinery that pulls in the nets.

Overall, our experimental nets performed well!  If you look at the graph below you can see both nets caught more Dogfish than the normal net it was being compared to (in this case the net right after).  We caught 3 Cod in the first string, of which our experimental net caught 1, and 0 Cod in the second string.

Thanks for reading!  We should have more data by the end of the week!

-JT

A nice Monkfish we caught the same day

Weekly Update #1

Hi everyone,

Pollachius pollachius aka Atlantic Pollock

This week was exciting as we received our first set of raised gill net data from the summer 2017 field season!  Our fisherman from Harpswell, Maine were using our experimental nets alongside their standard nets to catch Pollock this past may.

Compared to our data from last spring (previous data can be found under "results" tab), this year's data looks a bit different.  One of the first things we noticed was that our experimental nets were catching an equal amount / less Pollock than the standard nets.  One of our goals for this project was to ensure that Sea Grant experimental raised gill nets were catching an equal amount / more target fish than the standard nets.  Last spring, our experimental nets were clearly catching more target fish than the experimental nets.  This spring, our nets often caught less fish.

Another goal of the raised gillnet was to reduce the amount of Cod bycatch.  This new data shows that our experimental nets didn't do an adequate job in reducing the Cod catch.  Although these results don't support our goals necessarily, it is still early in the season, and this is the first time we have seen these sorts of results.

After talking with the Captain, he said this spring has been much more "alive" and variable than previous springs.  He stated that there is more feed around, and that it is higher in the water column.  With these observations, he said the Cod have been higher off of the bottom as well.  

This goes to show that fish behavior is extremely variable.  Maybe the variability in behavior this spring is the cause of our peculiar results?

Stay tuned for future data!!  Talk to you next week.

Blog is almost ready to go!

Hi everyone!  With gill net season right around the corner, I present to you the new blog where I will post about my weekly field data collection sessions, thoughts from the fisherman using our gear, and results from our research!  I hope that fishermen/women and the public alike tune in to hear first hand the results of our local research.

Over the next few days I will be posting explanations about our projects, but in the mean time, check out the results from last field season, and read an explanation of the goals of our project.

Thanks for reading.
JT

A nice day out profiling benthic water temperatures with Eastman's Fishing Fleet.

NHSG New Fisheries Blog!

Hi Everyone!

It's summer '17 research tech JT bringing to you a brand new blog detailing the happenings and results of our NHSG fisheries research!  I plan to detail our ongoing projects, introduce some important people and partners, and do a weekly recap of my field sessions.  I'm not a blog expert, but stick around to see some awesome research!!