Celtic Sea Herring Acoustic Survey 2016

Introduction 

Every year since 2004, an acoustic survey of the winter spawning herring stock which can be found in the Celtic Sea off southern Ireland has been conducted by the Marine Institute from the state research vessel, RV Celtic Explorer. The Celtic Sea Herring Acoustic Survey (CSHAS) will be carried out once again this year across three weeks during October. Working alongside the fisheries survey, a team of seabird and marine mammal observers will be on board, documenting the distribution and abundance of top marine predators often associated with herring and sprat in the Celtic Sea region.

Proposed tracklines for the October 2016 Celtic Sea Herring Acoustic Survey

The seabird team hails from the Marine and Freshwater Research Centre, GMIT and is led by PhD student Niall Keogh. This year marks the fifth in which seabird surveys will be carried out during CSHAS. Building data time series such as this forms the basis for Niall's research on seabird ecology in Irish offshore waters as well as feeding into the Celtic Sea Ecosystem Tipping Points project.

Gary Kett has joined the seabird team this year after spending the summer as a research assistant at the Shannon Dolphin and Wildlife Foundation in Kilrush, Co. Clare.

Meadhbh Quinn will carry out marine megafauna surveys for Irish Whale and Dolphin Group (IWDG) from the crow's nest, continuing long term monitoring of whales, dolphins, seals, turtles etc. during CSHAS over the past twelve years by the group. In addition to acting as coordinator for the Shannon Dolphin and Wildlife Foundation centre in Kilrush, Meadhbh is also the current Membership Officer for IWDG.

Blog readers can stay updated with our progress over the course of the next three weeks by checking in every few days here or on our Facebook page to view the latest pics and sightings. We hope you enjoy!...

From left to right: Niall Keogh, Gary Kett and Meadhbh Quinn (c) Usna Keating

Day 1: Friday 7th October

Mobilisation for CSHAS 2016 on board RV Celtic Explorer took place on Friday afternoon at Galway docks. After a safety tour and scientific staff meeting, we set sail at 8:30pm in order to make our way towards Dunmanus Bay in West Cork for Saturday afternoon where the fisheries acoustic equipment will be calibrated before beginning the survey transect lines.

RV Celtic Explorer docked in Galway and the pilot boat seeing us out safely that evening (c) Niall T. Keogh

Day 2: Saturday 3rd October

Dawn on our first day at sea saw us steaming south past the Blasket islands, Co. Kerry. After a hearty breakfast, the seabird and marine mammal observers headed out on deck for a few hours to 'get the eye in' before reaching the survey transect lines. 

From the off it was a busy morning, as is always the case in this area during autumn. Flocks of sooty shearwaters wheeled about to and fro as if in search of something hidden from our eyes, only later to consolidate themselves under groups of diving gannets which gave away the presence of lunge feeding baleen whales. All this foraging activity was due of the bounty of sprat in the area, as observed by the fisheries team monitoring what is present in the  water column underneath the ship as we go.

In total we observed four minke whales amongst feeding flocks of seabirds and had an all too brief encounter with a single humpback whale, blowing and surfacing several times as it made a beeline for a feeding group of seabirds and whales just a few kilometres to the southwest of the Skelligs.

Common dolphins followed the ship throughout, as expected. Our third cetacean species of the day will no doubt be our most abundant species for the rest of the trip. Rounding off the list of 'marine megafauna' was a single ocean sunfish, being tended to at the surface by a lesser black-backed gull (presumably checking it out for parasites to pick off and eat?).

The seabird tally for the day ended up at a respectable 16 species: gannet, fulmar, sooty shearwater, Manx shearwater, Balearic shearwater, European storm-petrel, great skua, Arctic skua, Herring gull, lesser black-backed gull, great black-backed gull, kittiwake, common gull, guillemot, razorbill and puffin. 

 Minke whale lunge feeding on sprat among flocks of gannets and shearwaters (c) Niall T. Keogh

Close up of the lunge feeding Minke whale (c) Niall T. Keogh

Skelligs (c) Niall T. Keogh

Common dolphin (c) Niall T. Keogh

Sooty shearwater (left) and a Balearic shearwater (right). Note the differences in size, structure and colour (c) Niall T. Keogh

1st calendar-year lesser black-backed gull (c) Niall T. Keogh

WESPAS Days 20 to 25: southern Celtic Sea to northern Bay of Biscay

Day 20 to 25 sightings: 23rd to 29th July 2016

After somewhat of a lull in cetacean activity in the mid Celtic Sea region, things started hotting up (literally!) as we approached the southern reaches of the Irish offshore territory and into UK and French waters. The sea surface temperature peaked at around 18°C and the ocean sunfish were out in force, as were common dolphins, with several groups seen every day ensuring the marine mammal observers were kept busy. We also recorded several breaching tuna, which looked to be bluefin and albacore. Our hoped for leatherback turtles didn't materialise however.

The outermost survey transect lines brought us close to or just over the continental shelf edge, an area of high productivity where several fin whales and even a single striped dolphin were noted. While surveying near the shelf edge along the northern end of the Bay of Biscay one evening, we spotted two very tall blows out towards the horizon line on our starboard side, presumably from fin whales. Soon after, another group of three fin whales crossed the path of the ship ahead of us from port to starboard, offering fantastic views.

Hard to beat good looks at the second largest animal on earth! 

Fin whale (c) William Hunt

 Fin whale (c) William Hunt

Fin whale (c) William Hunt

Fin whale (c) John Power

(you can just about make out the white colour to the right-hand side of the lower jaw in this pic, a diagnostic ID feature for the species)

We had some really nice sightings of bottlenose dolphins too, both near the shelf edge and also over the shallower shelf waters. Each group seemed to give the ship a wide berth, travelling past at distance. We tried to take as many pics as possible to see if we can match them to any known group (bottlenose dolphins with distinctive notches, scars and colourations on their dorsal fins are catalogued across Europe). It would be great to find out which group these animals belong, 'offshore' or 'coastal'?

Bottlenose dolphins (c) William Hunt

Common dolphin (c) William Hunt

Common dolphins (c) Mick Marrinan

Ocean sunfish (c) William Hunt

Sightings of cool marine wildlife have not just been limited to daylight hours. While on transect lines, the ship stops on station at night from midnight to 4am as part of the method for surveying boarfish. During this time a whole manner of life is attracted to the waters around the ship, illuminated by the lights. Fish such as saury start appearing in their droves to feed on gathering plankton which in turn attract predatory species like garfish, blue sharks, common dolphins and even seabirds such as fulmars and European storm-petrels (plus a grey phalarope one night circling the ship, calling!). 

This nocturnal wildlife spectacle has provided the night shift scientists and crew with endless entertainment (the blue sharks stealing the show, hands down). Even some of us day shift observers had to stay up way past our bed time in order to witness it!

Blue sharks (c) John Power

Blue shark (c) John Power

European storm-petrel circling RV Celtic Explorer at 2am (c) Niall T. Keogh

The seabird list finished up on a total of 26 species with the latest additions being Barolo shearwater, grey phalarope and yellow-legged gull. 

Barolo shearwater (which breeds on Atlantic islands such as the Canaries) was a real highlight as it is a rarely observed species around Irish and UK waters but more often seen in the Bay of Biscay, so the bird we saw travelling north with a Manx shearwater just inside the UK offshore territory some 270km southwest of Scilly was perhaps just about on the edge of its perceived regular range, although it seems we have a lot more to learn about their occurrence closer to home as this tracking study has shown.

A flock of 17 grey phalaropes was flushed ahead of the ship on the evening with lots of fin whale activity near the shelf edge along the north side of the Bay of Biscay. These pelagic waders (which feed on zooplankton) will already be on their way south to wintering grounds off the west coast of Africa. On examining pics of the flock, it appeared that quite a few females were present. Grey phalaropes breed in the High Arctic, where the males incubate the eggs and safeguard the chicks during the breeding season while the females leave soon after the eggs have been laid so it is not surprising that we have seen a flock of mostly females this far south already. Their work is done!

A quick check of the gull flock following the ship while west of Brittany yesterday afternoon produced a single fresh juvenile yellow-legged gull, as expected, but enjoyed immensely by the gull enthusiasts on board (...enthusiast, to be precise!).

Otherwise, the past week for the seabird team has been spent soaking up excellent views of yet more Cory's shearwaters and great shearwaters, a very good showing of European storm-petrels and some long-tailed skuas. A few more Wilson's storm-petrels were also seen, bringing the tally for the trip up to 13 individuals. 

Cory's (left) and great (right) shearwaters (c) William Hunt

Cory's shearwater (c) William Hunt

Great shearwater (c) William Hunt

Juvenile lesser black-backed gull (c) Niall T. Keogh

 Gannet (c) William Hunt

Gannets (c) William Hunt

After 25 days at sea, the Western European Shelf Pelagic Acoustic Survey (WESPAS) has come to an end. We are docking in Falmouth in Cornwall this morning from where we will make our way home to Ireland, giving us plenty of time to reflect on the fantastic marine species which we have had the privilege of seeing over the past few weeks. From here the RV Celtic Explorer will make its way to Germany to  undertake another survey.

We'll finish up with a pic of the final species list for the survey and a heartfelt thanks to Chief Scientists Ciaran O'Donnell and Graham Johnston (Marine Institute) for their continued support of offshore marine mammal and seabird surveys and to the officers and crew of RV Celtic Explorer for all their valued assistance throughout the cruise. Until next time... 

WESPAS Days 14 to 19: The Celtic Sea - a song of sun and fog

Day 14 to 19 sightings: 17th to 22nd July 2016

After the hectic day off the Blaskets on 16th July (see previous blog post), we made for Castletownbere in West Cork to carry out a mid-cruise crew change and take on some fresh provisions (which included a new coffee machine and fresh bananas!). Here we said goodbye to Dr Joanne O'Brien and Killian Coakley (GMIT) and said hello to William Hunt (MaREI/UCC) who joins the marine mammal observer team for the remainder of the trip.

The Marine and Freshwater Research Centre GMIT/Irish Whale and Dolphin Group team (from left to right): Sean O'Callaghan, Mick Marrinan, Killian Coakley, Dr Joanne O'Brien, Niall Keogh and John Collins

William Hunt (MaREI/UCC) on duty in the crow's nest

On leaving Castletownbere, we were treated to some nice sightings at the mouth of Bantry Bay just west of Sheep's Head. Common dolphins were plentiful, surfacing regularly among flocks of Manx shearwaters, auks and European storm-petrels and interspersed among these, a couple of minke whales, harbour porpoise and Atlantic grey seals.

Just as we cleared the bay, the dreaded fog set in, something which we were to be be plagued with for the next few days. This limited our survey effort during daylight hours with visibility often down to less than 100m. What made it all worse was that we could tell that just beyond the fog, somewhere, was bright sunshine and calm seas! 

Minke whale (c) Mick Marrinan

Common dolphins (c) John Collins

In time the conditions improved and as we made our way further offshore along the southbound survey tracklines into the Celtic Sea. The fog began to dissipate and we got our fair share of the glorious weather which everyone back home was out enjoying at the same time. And it was hot! 

With the wind at our backs and a following sea, we were fortunate to have a couple of days of superb survey conditions which produced some surprising sightings. Cetacean and seabird numbers were relatively low but the light easterly winds associated with the high pressure allowed some unusual migrants to make their way to the ship including a bat which spent some time flying around the crow's nest approximately 102km southeast of Galley Head, Co. Cork! Pics were posted online to see if it could be identified but without some clear shots of the ear and exact measurements of the wing it is unlikely that the issue will be resolved 100% (but thanks to everyone who made suggestions).

This follows on from a record of what is thought to have been a Leisler's bat, also present on RV Celtic Explorer at sea south of Cork in October 2015, so this sighting is not without precedent.

In addition to turnstone and whimbrel which were recorded west of Galway earlier on during the trip, other terrestrial migrants seen around the survey vessel in the Celtic Sea included a flock of 4 dunlin, a common swift (looking very out of place), a lost racing pigeon and a silver y moth!

Bat species (c) Niall T. Keogh

Racing pigeon (c) Niall T. Keogh

Quite a few jellyfish about too including mauve stinger (Pelagia noctiluca), compass jellyfish (Chrysaora hysoscella) and by-the-wind sailors (Velella velella). Lots of sightings of ocean sunfish also, including a group of three together and even some smaller individuals seen breaching fully out of the water! These oceanic wanderers eat jellyfish so looks like it's good times for them at the moment.

Velella velella (c) Niall T. Keogh

It has been an exciting few days for the seabird team with rare or scarce species dominating the tallies. We are out here at the perfect time of year for recording cool seabirds such as Cory's shearwater, great shearwater and Wilson's storm-petrel. Several hundred of the shearwaters have been noted, along with several instances of Cory's shearwaters tracking foraging groups of common dolphins. Fantastic to see these two top marine predators in close association, working the same aggregations of pelagic fish.

Among the flocks of European storm-petrels dancing over the water, a few Wilson's have been picked out (much to the delight of the observers) and while skua numbers have been low, all four expected species have been seen: great, pomarine, Arctic and long-tailed.

The seabird list for the survey is now up to 23 with the most recent additions being shag, common tern and long-tailed skua.

Great skua (c) Niall T. Keogh

European storm-petrels (c) Sean O'Callaghan

Wilson's storm-petrel (c) Niall T. Keogh

Great shearwater (c) Niall T. Keogh

Cory's shearwaters (c) Niall T. Keogh

Occupational hazard... airborne gannet poo hitting the crow's nest
(and the marine mammal observer!)

WESPAS Days 10 to 12: west coast shelf waters

Days 10 to 12 sightings: 13th, 14th and 15th July 2016

After finishing up our survey tracklines over the Porcupine Bank, we spent a few days checking out the shallow shelf waters to the west of Galway Bay. Seabird and cetacean species encountered here were those more typically associated with inshore areas, Manx shearwaters and common dolphins dominating the totals in each category. 

Sea conditions were variable and on the evening of 14th July, heavy mist and rain dampened our hopes of seeing much. Then at about 8pm while some 20km NW of Loop Head, we started noting a lot of common dolphins following the ship and foraging in association with rafting flocks of Manx shearwaters.

Scanning through these mixed groups later revealed a large minke whale which parted a flock of shearwaters in two as it surfaced and then all of a sudden, the unmistakable 'gnarly' profile of a humpback whale surfaced closer again! Those of us on watch at the time put a call out on the walkie-talkies and after gathering all observers together we were able to confirm the presence of three humpbacks around the ship! One of them even did us the honour of tail-fluking right off the stern of RV Celtic Explorer!

It was a real treat to see this group of large baleen whales not far from the Clare coastline. It wasn't all that long ago that humpbacks were considered a rarity in Irish waters, and now they are well known between Kerry and Wexford but their move into Clare waters seems to be a more recent development. How times have changed! (and what further changes await?)

Humpback whale tail fluking (c) John Power

Humpback whale (c) Niall T. Keogh

Humpback whale tail fluking off the stern of RV Celtic Explorer (c) Niall T. Keogh

Common dolphins are the 'bread and butter' cetacean species for any survey in Irish waters. While they are widely distributed and abundant, they are always a delight to watch, especially when following the ship on clear, sunny days. We've noticed at least three melanistic individuals among the various groups so far through the survey. These darker colour variants are infrequently encountered and can cause momentary confusion, almost looking like a different species. Check out Dan Brown's blog post about them on the Birding Frontiers website.

Common dolphins (c) Sean O'Callaghan

Melanistic common dolphin (c) Niall T. Keogh

Also included in our tallies for the past few days in this area was the first basking shark of the trip well west of the Aran Islands and a decent sized ocean sunfish, perhaps up to 2m in length, west of Kerry Head. 

Basking shark (c) Mick Marrinan

Ocean sunfish (c) Niall T. Keogh

A general increase in the abundance and diversity of seabirds was noted, as expected for inshore areas closer to the breeding colonies. It was nice to get good views of great skua, puffin, Arctic tern etc. as well as recording yet more Wilson's storm-petrels, this time two birds among a flock of 15 European storm-petrels some 40km southwest of Slyne Head on 13th July.

Great skua (c) Niall T. Keogh

Puffin (c) Niall T. Keogh

Two Wilson's storm-petrels and a gannet (c) Niall T. Keogh

Arctic tern (c) Niall T. Keogh

Fulmar (c) Sean O'Callaghan

So that brings us up to Friday just gone... next up a blog post about the seabird and cetacean feeding frenzy we encountered off the Blaskets on Saturday! (and what a spectacle it was) ...stay tuned