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rsn48 05-01-2019 11:22 PM

Forward sonar, whales etc & freaking out
So I will soon have forward sonar installed, good to 8 knots. And I live in an area with lots of sea mammal life like whales, sea lions, otters, porpoises,etc. I was just thinking today I can imagine me out in the Straight of Georgia half way paying attention cruising along when I see the massive whatever on the sonar, something in the water, appearing out of the blue, so to speak. Have you had that happen to you? Did you freak out trying to figure out what it was?

Ka_sea_ta 05-02-2019 12:17 AM

I've been fishing the west coast in my own boat since the early 80's. I'm a EE and always had been sorta of a geek when it comes to fish finders. I've had Westmar search light sonars 200 khz and 50 khz commercial gear, and spread spectrum when it was first introduced. I've had humpbacks surface with in 10 ft of the boat when we been fishing, I've had Orcas literally come with in feet of the boat when we been trolling. We have even had a seal jump on our swim step to excape Orcas. I've seen herring balls, ground fish, and rocks on the screen but I've never seen a seal, sea lion, Orca or whale. In short I'd be more concerned about logs and other debris then I would about marine mammals on the sonar.

MurrayM 05-02-2019 12:31 AM

We're photographers more than fishing people, so stop for Humpbacks on a regular basis. Last fall we were photographing a group of 14 from a respectful distance when two came slowly straight for the boat. They came within 10' and our daughter, who was in the pilothouse, called out, "Five feet on the depth finder!" so yes, they do duck right under the boat.

Also saw what I thought was a deadhead, but turned out to be an Elephant Seal. All this within 10 miles of the marina in Kitimat on Douglas Channel.

Lepke 05-02-2019 02:36 AM

I spent many years on the water in the PNW and the North Pacific. I think you're more likely to hit debris, especially logs, rather than a marine mammal.

makobuilders 05-02-2019 06:58 AM

I almost T-boned a submarine in the Strait of Juan de Fuca, middle of the night, pitch black, sub not displaying flashing yellow, nav lights, nothing. That freaked me out more than any log I hit.

Also, did hit a sunken motor yacht (the flybridge) right after Hurricane Andrew. Luckily it hit our hull and not the prop.

soin2la 05-02-2019 10:20 AM

I think rsn48 might be alluding to not knowing what you are suddenly approaching; old growth root ball, mammal or shipping container.

JDCAVE 05-02-2019 12:34 PM

We hit a humpback, just south of Klemtu. It was a bejesus “WWWHHHUUUMMMPPP”. The whole boat (40,000 lb of KK42) shuddered. It wasn’t a log which would have been more of a loud bag.

We felt awful! We stopped the boat and looked behind to see a couple of spouts 1/2 a nm aft of us. We were pretty sure the running gear didn’t contact the whale but the whale certainly probably felt it alright. As I said we felt terrible for the animal. We called it in to Coastguard and later that night (anchored in cell reception in the Klemtu area) a DFO biologist phoned to get further details. She agreed with our assessment that it was a whale strike.

Unlike killer whales, humpback whales do not “echo locate” and are completely unaware of vessels. I was at the wheel at the time and we suspect that that it was just surfacing at the point of contact.

I’m not certain that forward looking sonar will prevent a whale strike from a surfacing whale. It might help but it all happens so very fast.

rsn48 05-02-2019 12:54 PM

I'm to lazy to go look at a chart right now, heading to Victoria BC for the boat show in Sidney this weekend. But the area I'm referring to is about 900 feet deep so you can imagine how startled I'd be to discover I am about to plow into something a hundred feet from me, sight unseen, out in the middle of the pond, so to speak.

In fact, one area between Vancouver Island and Denman Island I was transiting with friends, first time out in the new old boat. I told my friend my boats draft is 6 feet (in reality more like 3 feet), we were transiting a very deep area when the depth sonar started registering 3 and 4 feet in the middle of the channel. We panicked a wee bit but when I look into the ocean all I could see was the dark green one associates with deep seas. I talked to a chap in the marina parking lot about two weeks latter about these false hits and he told me he had some friends experience the same false reading I had. The only thing that makes any sense was whales transiting.

Comodave 05-02-2019 12:56 PM

We were bring a previous boat down the coast from Seattle to LA. We had been fog for about 24 hours that was at times so thick we could not see the flag on the bow. The fog lifted a bit and dead ahead was a whale apparently dozing on the surface. At first I thought it was a rock, but we were about 8 nautical miles offshore. I started turning the wheel when the apparent rock moved. If the fog had not parted at the right moment we would have hit the whale. As it was we passed within 25 feet of it. I always thought that they would hear us long before we came anywhere close, especially since that boat had twin Detroits in it and they were not really quiet.

Jeff F 05-02-2019 05:51 PM

I got close to a humpback last week just off Cape May, in about 30 feet of water. I thought it was an overturned boat at first. It wasn't moving. When I got close it raised its head a bit, blew, and slowly dove. I've never seen them lounging around on the surface like that.

JDCAVE 05-02-2019 11:06 PM


Originally Posted by rsn48 (Post 762284)
The only thing that makes any sense was whales transiting.

Actually more likely a midwater scattering layer. Could be a school of herring, plankton, halocline, or some such thing. The area to which you refer (Baynes Sound) is a location of very high biomass of herring at certain times of the year.


rsn48 05-08-2019 01:07 PM

So I did a little research on Baynes Sound, much more biodiversity than I realized:

Biodiversity & EBSAs – Association for Denman Island Marine Stewards

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