Bonified newbie question

[Mello-Yello]

Here's one that's been pestering me;

Having grown up in the NW, but not spending much time offshore, I've seen the tide come in, then go out. I've learned to recognize the fast running tides and the slow (had to learn this to fish Hali's in Straight of Juan DeFuca). But all these places, when the tide comes in, it really does come in.

The question;

What does it do offshore? Does the water just get deeper? or does the current run faster and then slower?

Is it a practice to try and hit tides a certain way offshore for Halibut? or do you just add/reduce weight to find the bottom?

I can't believe I don't know this, but then again, I'd never heard about bananas either...

[Miss B Haven]

Tides do seem to affect the offshore currents and the drifts. No science on my part, just observation. They also seem to affect the way the fish bite and where they are holding (bottom, midwater etc). Good thread for some discussion- hoping to learn some more on this! :grin:

[CAPT KUJO]

As a diver, I can tell you off shore when the tide is high , the tops of the reefs are DEEPER. Also Just because you see current on top of the water going one way, often times as you are decending, and reach the bottom, current is going the opposite direction. Not much science here, way too many factors involved to get a "pattern"

CAPT KUJO

[ 04-12-2003, 06:14 AM: Message edited by: CAPT KUJO ]

[Orca]

Not that I know this stuff, but I just happen to be reading a book on this and other subjects called "The Fisherman's Ocean" by David A. Ross Ph.D. I think the bottom line for us is that our tidal currents are largely manipulated by the wind and our proximity to shore. But for halibut nearer the edge of the continental shelf, there may be some predictions about the current that could be made using his information. Maybe someday I will see the pattern and make some sense of it all.

I just happen to be in the tides and currents section, and here is what he has to say:

"It's easy to see tides near the shore, but they also occur to a lesser degree offshore, where the lack of a fixed reference point makes their up-and-down motion difficult to observe. Even out at sea, however, tides and tidal currents become visible when they flow over shallow areas of the seafloor, forming turbulent areas called tidal rips"

"Many coastal fishing areas, including inlets, small estuaries, and bays, contain a small volume of water campared to the open ocean; thus, the gravitaional attraction between this small amount of water and the sun and the moon (the cause of the tide) is relatively weak compared to what occurs in the open ocean." "The tides here, called 'forced tides', are caused by water being forced into or out of inlets by the tidal changes in the open ocean."

"A stong wind blowing in the direction of the tide caused current can obsure the tidal effect. Conversely, winds blowing in the same direction as the tidal current will increase the speed of the current. A change of 1 inch in the barometric pressure in a stationary low-pressure system can result in a 1 foot rise in the level of the tide; if the tidal range is small, the meteorological effect can be even larger than the normal tide."

"Out in the open ocean, away from the influence of land and shallow water, tidal currents move fairly slowly. Near the coast however, tidal currents are restricted by land, channels and inlets, and bottom structure or the bottom proper. These restrictions increase the water's rate of flow, which causes the current to intensify." "Often when the tides reach either their high or low mark, the water will go slack and the current will reverse or change direction. This general rule however rarely applies to nearshore or inshore areas where the land or the continental shelf interfers with the tidal waveeform."

"In offshore waters, where land or shallow water do not restrict the direction of flow of the tide, tidal currents often follow a rotary pattern and the tidal flow will be in all directions [over time]. The rotation of the offshore tidal current is caused by the earths rotation; unless influenced by other factors. The speed of the rotary current flow will vary throughout the tidal cycle, with two maximums and two minimums in each cycle; the maximums and minimums are usually in approximately opposite directions and are separated from each other by about 3 hours. This rotary pattern circulates around a position called an amphidromic point, which has no tidal height. The general pattern is similiar to water sloshing around a bucket." "If the coastal waters are relatively deep, the offshore rotary pattern can come close to shore, but the shoaling bottom and the presence of the coast will change the rotary tidal waveform as it approaches land. As the shoaling bottom and the presence of the coast restrict the offshore rotary pattern, the tidal current will flow in a back-and-forth manner, rather than in the rotary pattern."

[Mark Mc]

I think you really have to separate true tidal influence (which occurs in bays and nearshore areas, say within 20 fathoms) and what happens in deep water, which is dominated by currents. The dominant ocean currents are very seasonal, with a high flow in spring & summer (usually from the north), then slowing down in the fall, then reversing direction in winter. Then there are more local ("micro") currents (driven by the winds, temperature & pressure gradients) competing with the dominant currents. Every summer you have days when the current is screaming at 3 or 4 knots parallel to the coast. This current doesn't care if the tide is coming in our out at a specific moment. All this being said, sure the rising or falling tide can contribute to the formation of rips in deep water. But it's only one of many factors that determine "what goes on" underwater, like when fish bite, when/where bait congregates, when/where rips form, when temperature changes, etc.

Contrast this to places like S.F. Bay, where the tides decide almost everything that has to do with where the fish are & when they bite.

p.s. Orca, that last paragraph you quoted is especially interesting....that must relate to how & where the predominant currents behave in the E. pacific....the so-called Davidson current, California current, & Japan(ese) current. Any mention of these in the book?

[ 04-14-2003, 11:46 AM: Message edited by: Mark Mc ]

[jcarufo]

We have fished Vancouver Island for Halibut for the last ten+ years and were taught by the locals there that you always try to fish the 'Neap Tides' which are the quarter moon tides. If you look at your tide book they are the tides of the smallest change. In open ocean it might not make much difference, but we typically fish over reefs that typically will have currents present. If you can find someone that uses a computer program called Tides and Currents by Nautical Software it will visually show you the periods of the CURRENT that you want to fish. The flattest current is usually a little before or after the tide change. The program is really fantastic for both tide and current predictions and we also use it to time the Incoming/bite at bouy 10 and flow times on the Columbia. You come to realize that a slack tide is an important bite time, but when there is one, a slack current is even more important. We fish Swiftsure Bank off Port Renfrew and the numerous banks including the 23 mile bank off Banfield and see distinct predictable slack periods in those areas. I don't see why the waters off of Oregon wouldn't be the same. In those slack periods you can fish your jigs or bait straight up and down requiring less line and more direct hook-ups.
Hope this helps a little. Try to find someone that uses the program. It will be worth your time.
Jean

One thing we saw in Canada last spring that might be worth a try for the bait users here is using the largest (5") 'Cop Car' Coyote spoon on your spreader bar rather than bait. We saw quite a few people on the Swiftsure Bank doing it with great success. You drop to the bottom, the spoon flaps in the breeze on a short leader until inhaled. It didn't seem to take long!

[jcarufo]

I just checked my Tides and Currents program and we're in luck as May 8, 9, and 10 are NEAP tides. Very little change from High to Low tide with slack current approximately 7AM, 2PM, and 8PM. Let me know if you notice a difference.
Thanks,
Jean

[Mello-Yello]

Yeah, when we fished the Straits, you had to pick those small tide changes. The amount of water pouring through there was incredible. If you tried hitting bottom on a big tide change, you'd hit bottom about a mile from where you'd dropped...48 oz wasn't uncommon even on a good tide. I was just wondering if we would see the same thing 20 miles offshore and if so, was it in any way predictable.

It sure was cool looking up and seeing a Trident Nuclear Submarine cruising by. I'd sure hate to snag one of those. : /

:shocked:

[Orca]

Mark Mc,

I don't see any mention in the book of specific currents in the Pacific. Not yet anyway.

[ 04-14-2003, 01:23 PM: Message edited by: Orca ]

[Mark Mc]

Here's some interesting reading on the subject if you can stay awake through it, especially part I California Current. I'm more confused now than before...

physical oceanography

another good link:
web page

quotes:
"The CCS (California Current System) extends up to 1000 km offshore from Oregon to Baja California and encompasses a southward meandering surface current, a poleward undercurrent and surface countercurrents. It exhibits high biological productivity, diverse regional characteristics, and intricate eddy motions that have puzzled oceanographers for decades."

"Because of the resupply of nutrients by coastal upwelling, the CCS has high biological productivity. Measurements from satellites, moorings and hydrographic surveys reveal tremendous heterogeneity in the distributions of chlorophyll and plankton, which impact the development of fish, birds, and mammals."

"A poleward undercurrent flows continuously along the shelf break from 33°N-51°N at an average depth of 200 m and speeds of 15 cm/s [Pierce et al., 1999]. A surface countercurrent (the Davidson Current) also flows northward, is associated with seasonal wind changes, and sometimes merges with the undercurrent. These new observations suggest a strong dynamical link between deep water flows and current regimes over the continental shelf and slope."

Do a Google search under "California Current" and a bunch of good hits come up.

[ 04-14-2003, 11:59 AM: Message edited by: Mark Mc ]