Posts Tagged ‘fish’

The beauty of Pacific herring

Herring-stuffed harbor seal

Herring-stuffed harbor seal

2011 is the first year I really started noticing the herring of the Salish Sea. In past years I’d notice the occasional glimmering ball of “bait fish” or “forage fish” from the dock of the Friday Harbor Labs or a bluff of convenience in the San Juans, but they were always pretty limited — typically isolated, not very dense, and about a meter across. But last summer I sailed through a tremendous herring run when transiting from the San Juans to Seattle and witnessed feasting — by minke whales, harbor seals, sea birds, and even a humpback. Then this fall the students and Robin captured underwater video clips of forage fish, probably herring, at Lime Kiln.

And then yesterday Robin mentioned seeing about 30 harbor seals chasing herring all around the docks at the Labs as we prepared to deploy a fish tag receiver on the far side of San Juan Channel with Tina and Chuck. While scoping out the site, she and I were pleasantly surprised to find a small school of herring very close to shore at Point George on Shaw Island. It was a glassy calm, sunny November afternoon, and it was quite beautiful to watch the fish swimming slowly in and out of the little rocky embayment.

Here are a few videos that capture the underwater scenery. After these sightings and some intriguing talks at the recent Salish Sea Ecosystem talks (in which Fred Felleman made it clear that we are not paying enough attention to our herring stocks — especially on this side of the border), I”m left feeling that these shiny fish warrant further study, appreciation, and conservation effort.

Does anyone else have herring highlights to share? How about handy ways to keep track of the status (2008 report) and dynamics of herring throughout the year?

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CO2: A Fish Drug

Isn’t it great having it warmer longer and being able to soak up the sun longer once summer is over?!  Maybe you know the reasons from various classes or the news.  Besides hearing how high CO2 levels are do you actually know how CO2 levels are affecting organisms physically?  CO2 is like a fish drug that is affecting their olfactory systems and desensitizing fish to instinctive behaviors.

A brief background – Ocean inhabitants, especially coral reef inhabitants, are sensitive to changes whether it is temperature, CO2 concentrations, or pH.  If CO2 levels continue to increase as they are, by the end of the century, there would be about 1,020ppm of atmospheric CO2 (more than enough to dramatically affect multiple marine organisms). Atmospheric and dissolved CO2 levels are linearly correlated.  If atmospheric CO2 increases, dissolved CO2 in the ocean increases simultaneously.  CO2 and pH levels are indirectly correlated.  If dissolved CO2 increases, pH decreases.  If maintaining down the current path, oceanic pH would decline up to 0.4 units, making the ocean even more acidic.

Munday et al. conducted a study to see the effects CO2 levels have on fish populations.  This study was looking at clownfish and damsel fish larvae and how they respond to three different levels of CO2.  The control was current CO2 levels (390ppm), 550ppm, 700ppm, and 850ppm.  Behavioral responses and olfactory cues from predators were noted and it was noticed how drastic the effects of CO2 levels really were.  With each increasing dosage the results were more significant.  Natural and instinctive behaviors are thrown off due to the destructive influences CO2 has on the olfactory system.  Instead of smelling predator cues and hiding, the increased CO2 levels cause clownfish and damsel fish to be less sensitized and alert.  The fish participated in increasingly risky behavior such as spending more time where predator cues were present, swimming farther from the protections of the reef, and being more active but less alert to predator cues.

The longer a fish is exposed the worse the symptoms.  Age also increased the severity of the symptoms.  Noting the same change in behaviors another experiment was conducted with predator encounters.  The more frequent, careless, and risky behaviors became the higher mortality rate climbed.

Not only do rising CO2 levels cause concern for species, but trying to sustain the species at risk becomes more complex.  Protecting an ecosystem may no longer be enough if fish are being easily preyed upon due to the severe behavioral effects of increasing CO2 levels.  Assuming other marine species will exhibit similar responses, the effects of rising CO2 on biodiversity of marine ecosystems could be significant and the effects irreversible.

Chinook salmon are already endangered and, if the hypothesis is correct, the increasing dissolved CO2 levels could be an additional threat.  Chinook, being the Southern Residents primary food source, may have a crucial impact on the killer whales if they cannot handle the added stress from rising CO2 levels.  Will the Southern Residents adapt to the CO2 levels or will they suffer as much as the Chinook and other marine organisms?

The 4 students in the Fall 2011 session, along with past and future students, will study the environment and see how different factors affect the killer whales.  Students are looking at relationships between the whales and salmon, human influences, and natural influences.  We all start our first expedition Sunday (18th) to start collecting data for our final projects. Watch for our final projects as time moves forward!

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New fish detectors in the San Juans

Thanks to a calm weather window and the on-going support of collaborators at the University of Washington and NOAA/NWFSC, we were able to re-deploy two fish tag detectors along the west side of San Juan Island in the first days of 2010. We plan to re-deploy a third in the first quarter of 2010. Stay tuned for a separate post summarizing what fish were detected in the last year or so. In the interim, here are some notes and photos from the field work.

Saturday 1/2/10:

During a hydrophone maintenance dive, Jason Wood and I deployed a new Vemco fish tag receiver (VR2W SN#100905) at Lime Kiln lighthouse. We supported the receiver on doubled crab pot line with a salvaged WDFW float (#3398) and anchored it with about 10 liters of concrete in a paint bucket with rebar/PVC legs. A length of chain embedded in the concrete served as an attachment point for both the receiver mooring (clipped on with a taped SS carabiner) and a tether which was tied to the first hydrophone stand.

The Lime Kiln mooring location is about 30m west of the iron bar near the high tide mark adjacent to the SW corner of the lighthouse. The mooring anchor depth is about 10m.

The highlight of the dive was Jason finding the old VR2W (SN#100914). After we had been led astray by an old yellow line, I was pretty sure we were in the wrong spot and wouldn’t have enough air to search for the old mooring. Yet we had to be close because we had encountered one of the old hydrophone stands whose pair should have been within about 10m. I was thinking about whether the old hydrophone stand might have been moved by the pesky Lime Kiln currents when Jason waved in front of my face. I looked up to see him smiling around his mouthpiece, the algae-encrusted old mooring in his grasp. It was a cinch to raise it with the lift bag and the exfoliated kelp hardly slowed our return to shore.

The VR2W looked great and the red light was confirmed still flashing once uncovered at the lighthouse picnic tables. The float was pretty overgrown with algae and the indelible ink was no longer legible.

Orcasound mooring ready to deploy

Orcasound mooring ready to deploy

Sunday 1/3/10:

While the leaded line tethering the Orcasound VR2W to shore was intact as recently as NN months ago, when we looked for it late last night we found only a short section still attached to the intertidal eyebolt. Luckily the other end was found only a few meters away, pinned under a boulder by 10 cm of gravel. The remainder was entangled in nearshore subtidal rocks, but I managed to tease it out by wading around. I was able to wade to where it was attached to a braided nylon line. There I attached a crab pot float and then re-secured the leaded line to shore.

This morning, Liam helped Val and I pick up the float and back away from shore while taking up the nylon line. The mooring came up fine (though a thicker line for that concrete weight would be easier on the hands) and the red light on the VR2W (SN#100913) was still flashing!

After laying out the new hydrophones (to ensure we didn’t overlay the new Vemco tether), Jason paid out some extra slack in the leaded line. I reattached the nylon line to the leaded line and we drew this longer line tight above the water and maneuvered Cat’s Cradle until we had a clear path straight offshore through the kelp. I attached the new VR2W (Serial Number 100912 moored on the line/float from Lime Kiln recovered yesterday) to the SS hoop in the concrete mooring weight, lowered away, and Liam helped me slip the line. It was pretty slick and fast. It should be interesting to see how the leaded line fares this next round.

The Orcasound mooring location is about 30m offshore of the lowest eyebolt (latitude = 48.55823212, longitude = -123.1737158; UTM y = 5378363, UTM x = 487182). The mooring anchor depth is about 7.7 meters below mean zero tide level.

Here is a spreadsheet that lists all Beam Reach deployments of Vemco receivers:

http://spreadsheets.google.com/ccc?key=tm3KyXdwdOkXl2CWRrVTUww

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Fish hydrophones in the San Juans

Today Val and Scott re-deployed a Vemco VR2 fish tag receiver at Lime Kiln State Park. This receiver, provided for this pilot study to Beam Reach by Fred Goetz, will help marine scientists understand how juvenile and adult salmon use the San Juans, in addition to any other passing fish that have been “tagged” (surgically-implanted) with 69 kHz acoustic tags. We at Beam Reach are most interested in the behavior and distribution of adult Chinook salmon, and secondarily any other potential prey of the endangered southern resident killer whales.

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The photos above show the mooring prior to being snorkeled down to the pier block that remained from the previous deployment (last November).

Two other VR2s have been provided by Kurt Fresh of NOAA.  (Their serial numbers are: 100910; 100913.)  One will be deployed on the west side of San Juan Island; the other will be placed near Cattle Pass.   We’ve mounted them on short (~2.25m) mooring lines (1.25cm diameter 3-strand poly), supported by single yellow shrimp pot floats (see below).  The base of the receivers will be ~0.75-1m above the bottom.  The floats will be ~1m above the top of the receivers.  The mooring weights are either ~25kg concrete slabs (35cm x 35 cm x 15 cm; see below) or paint buckets filled with cement.  Both types of weights have metal hoops or chain for attaching the mooring line and for lowering during deployments from a boat.

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Data and analysis from these deployments will be documented in the Beam Reach science wiki

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Listening for Lime Kiln fish

IMG_7032.JPGLast Sunday (11/09/2008), Jason Wood and Scott Veirs deployed a receiver that can detect and record the signals emitted by acoustic tags implanted surgically in migratory fish, like the Chinook and chum salmon that southern resident killer whales appear to prefer.  The Vemco “VR2″ receiver, provided by Fred Goetz through a collaboration with UW Fisheries, was deployed during a scheduled maintenance dive on the hydrophones at the Lime Kiln lighthouse.  The plan is to retrieve the VR2 in early 2009, download any serendipitous detections that may help in the interpretation of the echosounder data (to be presented at the Puget Sound Georgia Basin conference), and then redeploy it for the remainder of the winter (and perhaps the entire year).

The dive went well and lasted from about 11-12am.  We enjoyed visibility of about 20m and pleasantly calm seas (it was very rough on Saturday when we initially planned to dive).  We cleaned and secured the intertidal hydrophone and echosounder cable protectors, checked the VR2 mooring for buoyancy, and then followed the hydrophone cable to the two hydrophone stands (cement-filled paint-buckets with a broad tripod of embedded rebar).  The VR2 was deployed 3m NW of the southern hydrophone and its mooring anchor was tethered to that hydrophone stand’s embedded chain and one of its rebar legs.

The VR2 mooring had a total height above bottom of 2m, with the receiver hydrophone oriented upwards about 1.4m above bottom.  Since the mooring was deployed in 9m of water when the tidal height was ~2m, the depth of the receiver is about 6m below the tidal datum (0m).  The mooring consists of a ~2m length of 1/2″ 3-strand polypropelene line connecting a ~3kg buoyancy crab float (used in lieu of an incompressible trawl float since minimal compression is expected at this depth), the VR2 (cabled-tied through and around the strands), and a stainless steel threaded shackle (bowlines at both ends).  The shackle connects to a loop of 3/16” plastic-coated wire rope that extends through a pier-block (via a 3/4 inch hole drilled through center line).  The loop is secured with a clamp and is attached via sheet-bend to the ~4m-long tether (same type of line).  All knots’ tails are secured with electrical tape.  The float is marked with UW Fisheries research and Scott’s cell phone number.

Detailed photos of the mooring, including closeups of each component are available in the Beam Reach gallery.

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