In general, I want a little more evidence than this before declaring global catastrophe.
For example, I'd like to get confirmation of the problem from NOAA[1], particularly the NMFS[2]. Alternatively, Green Peace[3] would no doubt be one of the first organizations to raise an alarm - they care about the ocean, and presumably gather signals from many sources. I want confirmation because the simple fact is that it's impossible to get a comprehensive picture of the Pacific's health from one voyage - there are too many variables at play.
The skeptic in me questions the tacit assumption (the one that makes the OP's observations so troubling) that the entire Pacific is normally teaming with fish. However, I assume that fish travel in schools, and that fish density is wildly variable. E.g. there are normally vast swaths of the Pacific that are "dead". Indeed, anyone going out to fish for sport knows that fish aren't uniformly distributed, and they don't stay in one place. In the open ocean, these schools are vast, but so are the dead zones when there are no schools.
That said, not being in the field, I'm not sure how we gauge the health of an entire ocean from a "supported biomass" perspective. Nor do I know anything about who would be responsible for officially raising an alarm about global catastrophe. Or if they did, what we could do about it. It seems like the only thing we really could do is reduce the rate at which we harm the ocean, rather than dumping into it.
You are right to be skeptical in the fact that anecdotal evidence from a yachting voyage could establish a general case for mass bio-mass (or lets just say a sub-set of bio-mass, like catchable fish) decline, and your point that large portions of the Pacific are normally dead-zones is true because of the way that anoxic regions can develop due to oceanic circulations of nutrients and dissolved oxygen concentrations.
But, you might be concerned to learn that the NOAA typically only reports on mass die offs fairly close to US shores, at least within our EEZ zone- because they are only adequately funded to do so- [1] is an example of such a report. There is no well-funded transnational environmental authority that can make a reliable 'alarm' about the potential of mass common-water oceanic die-offs (think 'tragedy of the commons'); Greenpeace is more of an advocacy organization than a scientific or monitoring authority.
One thing we can indirectly empirically gauge is the size of these large garbage patches at sea simply via imaging. In fact NOAA has put together a fact sheet on this [2], although it is rather simplistic. What we can glean from this is the fact that they are real, quite large, and if you look at the map it looks as though the OP's voyage passed through it at least once if not twice. Which would explain much of what he saw, but not necessarily the consistency (pervasiveness) of the dead zones observed..
Finally, just food for thought (er.. perhaps bad choice of words.. haha) that there is a sort of conflation in the article about the long-going decline of fish stocks and accumulation of garbage due to dumping and the more acute poisoning/death of fish stocks due to radioactive leakage from Fukushima in the areas off-coast Japan specifically. There is academic evidence [3] that large fish, specifically tuna, are acting as vector to transport large amounts of spoiled biomass as far afield as California. How much of the biomass die-off does this explain? I have absolutely no idea, but since both issues are quite concerning in their own right we should probably keep tabs on both..
I have to disagree with you regarding waiting for confirmation from NOAA, NMFS and Green Peace. From strictly personal experience, growing up in the mediterranean and being the 2nd generation of spear fishers, sailors and divers, living in resort/tourist destinations for the majority of my life; waiting for confirmation from resource-strapped government agencies is sticking your head in the sand. I've seen the decline of fish first hand since I was a teenager.
Focussing on the Pacific Ocean, and this specific article would be to forego the magnitude of the problem. We removed smoking areas in restaurants because, as one wise man said it "its like having a pissing area in a pool", I believe the same can be applied to the ocean.
Green Peace have already reported on similar problems [1]
So have the NOAA & NMFS [2]
In countries like Mexico, economic stimulus is prioritised as most mayors/local governments live on a 4 year stint to make an impact, resorting to populistic moves that the unfortunately ignorant populace will follow. Prioritising development of real estate, hospitality, touristic developments that are by no means sustainable. Making sure everyone has a job. I'm by no means arguing that these are bad things, I've made my career in the field but these are again, by no means sustainable. Long term investments into education are left secondary, effects of which are already felt [3]. I'm talking about the destruction of sea turtle nesting grounds, the destructions of mangroves that nourish the reefs, water sewage directly in the ocean[4], the killing of sharks[5] and much more.
Italy, where most older fishermen can barely read nor understand what their daily labour actually does to the ocean is facing a crisis across all coasts. There's just no fish left to sustain its industry. [6]
Its hardly new any of this. Jacques Yves Cousteau reported on this long ago. [7]
Know that everything around you will eventually turn into waste, we are at a point in history were we have enough alternatives to not damage. I agree with you that all we really could do is reduce the rate at which we harm the ocean. Its time to make educated choices.
For example, I'd like to get confirmation of the problem from NOAA[1], particularly the NMFS[2]. Alternatively, Green Peace[3] would no doubt be one of the first organizations to raise an alarm - they care about the ocean, and presumably gather signals from many sources. I want confirmation because the simple fact is that it's impossible to get a comprehensive picture of the Pacific's health from one voyage - there are too many variables at play.
The skeptic in me questions the tacit assumption (the one that makes the OP's observations so troubling) that the entire Pacific is normally teaming with fish. However, I assume that fish travel in schools, and that fish density is wildly variable. E.g. there are normally vast swaths of the Pacific that are "dead". Indeed, anyone going out to fish for sport knows that fish aren't uniformly distributed, and they don't stay in one place. In the open ocean, these schools are vast, but so are the dead zones when there are no schools.
That said, not being in the field, I'm not sure how we gauge the health of an entire ocean from a "supported biomass" perspective. Nor do I know anything about who would be responsible for officially raising an alarm about global catastrophe. Or if they did, what we could do about it. It seems like the only thing we really could do is reduce the rate at which we harm the ocean, rather than dumping into it.
[1] https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospher..., http://www.noaa.gov/
[2] https://en.wikipedia.org/wiki/National_Marine_Fisheries_Serv..., http://www.nmfs.noaa.gov/
[3] http://www.greenpeace.org/usa/en/