Climate Change and Ocean Fisheries
Gary D. Sharp
It is possible that the most adaptable humans on the earth are those that live on small oceanic islands.
It is a simple fact that the majority of island populations are descended from early seafarers, and that often the oceanic islands were colonized by sailors and their families in some quest for new opportunities. The histories of many island people is a series of tragedies, and sagas of brave endurances of both long and short term climatic events and processes. It is also a fact of life on many islands that sporadic seismic and volcanic upheavals occur as the islands shift, to grow or subside, as part of great tectonic battles over the surface of the earth. The other contextual factors that determines the fates and activities of island populations include their situation within ocean climate regimes, and such important factors as whether the islands were formed by upthrusting solid earth crust like the Seychelles or Madeira, rapid or slow volcanism like the Hawaiian Islands or La Réunion, or formed by slow accretion of coral organisms over subsurface mounts and ridges like many of the western Pacific islands or the Maldives. These factors determine the shapes and island border characteristics, and whether there are suitable ports or landing beaches.
No matter what the origin of the island, or the human population, the major determinants of survival are those of the climate and seasonal patterns of the surrounding ocean, as these determine the patterns of production from both the land and from the sea.
Those island situated within regions of greatest climatic and oceanic variability appear to provide the greatest opportunities for their human inhabitants to adapt and expand their range of activities, from agriculture, animal husbandry and fishing. Some of the more Idyllic, tropical island situations provide fewer options, and in some cases severely limit the opportunities that are enjoyed in other, more harsh climates. Even the localized problems associated with ciguatera in the tropics, or seals at high latitudes, or other species associated situations shape the responses of societies, and their options. Conditions such as seasonal wind patterns and sea swell and wave heights affect each island community, although these are often taken for granted by arm-chair travelers.
The various points that I wish to convey within the following survey, sketches and comparisons of local and regional climate and oceanic patterns will center on the available historical climate/ocean records and their societal consequences.
The first and foremost point is that climate always changes, in a not-quite chaotic fashion.
This is very important in the sense that ecological systems tend to stagnate under uniform conditions, particularly the oceanic ecosystems. Ecological productivity and complexity is stimulated locally, and then it is extended by turbulent hydrodynamic processes and food web dynamics over time and space scales that are too often unappreciated (c.f. Bakun, et al. 1982, Cury and Roy, 1989). The importance of "shocks" and events is of paramount importance in oceanic environments, if for no other reason than to stimulate the enrichment of the photic layer so that production can be sustained. It is important that we note that the major difference between the ocean and the terrestrial environment is that there is a clear size hierarchy in the ocean food webs, and that this also is associated with the scale of capabilities for each species to control its own position and therefore its physiological environment, through active motion, within the various ocean gradients.
Another very important variable, too often ignored by ocean scientists is the role of light on the entire ecological production process.
Seasonal processes and climatic atmospheric events stimulate the upper ocean mixing and regeneration of nutrients from within and below the thermocline. These processes, in turn, transport relatively passive organisms back into the upper photic levels, which have for one reason or another arrived below the photic layer Smetacek (1985, 1988). These processes can be modulated on daily and local scales, or on climate scales. For example, wherever cloud cover persists and diminishes the available light and heat, and therefore their penetration of the upper ocean, the upper ocean mixing is lessened.
In cloud covered areas, calm seas means diminished production, and strong winds, or storms provide the all-important upper ocean turnover, and nutrient upwelling that in terrestrial environments man has enhanced by use of the plow and pump.
Only in special areas of the oceans margins have humans begun "tilling" and harvesting their "fruits de mer". The unfortunate situation is that many potentially fruitful sites have been otherwise utilized, at a great loss to the potential yield from culture activities around the world.
There are many degrees of comparison that can and have been made between the land and the sea, but the most obvious distinction is that humans have only recently been able to affect the oceans, as they have the land, and mostly this has been in a poorly understood and perhaps less than thoughtful fashion.
Among the major island nations, Japan has made the greatest progress toward extensive cultivation of marine species, although the basis of their successes are twofold. First is the fact that their culture efforts are supported by an immense economic engine in their local markets. Second is the all important fact that their fish culture activities are sustained almost exclusively by the recent decade’s great abundance and availability of the far east sardine (Sardinops melanostica ), which is harvested and used as a cheap source of protein for their fish culture activities. Few locations in the world enjoy both these important benefits.
What has all this got to do with climate and ocean fisheries? At the Second Week of Fisheries, here in Horta, I pointed out the issues of costs of operations versus yields from high technology, high yield fisheries. One result of having heeded that advice has been the Azores’ exemplary development of modern, low technology fisheries that deliver products to high value market places. To reinforce that progress, let us look at a few recent issues, from global climate change, to the cost of petroleum products, to the price of tuna sandwiches, and their sources.
Climate Change – A Fact of Life
The history of human society is a study of climate dynamics.
Unfortunately far too few physical scientists have a good perspective on these processes, and the recent clamor over "Green House" warming leaves a lot of room for debate and contentious bickering that continues to threaten credibility of the global science community. Another unfortunate fact is that careful, systematic observation of the world climate is only now emerging, after more than a century of building an atmospheric observation capability. The 70 percent of the planet that is ocean, and that contains more than 95% of the sensible heat in the fluid envelop of the planet, including the atmosphere, is so poorly measured, and for such short periods in those places where measurements are collected in any routine fashion, that no credible projections, or even hindcasts, can be made.
I will provide a few examples that should prove my point. Bakun (1990) provides a series of observations about the surface wind-driven upwelling in five scenarios for four eastern boundary current regions (Figure 1). These data sets were selected by Bakun because they were well documented, and comprise the best available time series for the recent period of systematic instrumental measurements, 1947 to present.
I have also been provided with a series of regional summaries of the winter seasonal departures from the long-term means of surface scalar winds (and sea surface temperatures) from the Comprehensive Ocean and Atmosphere Data Set (COADS) by colleagues at NOAA’s Environmental Research Laboratory, Climate Research Division (Figure 2). It is notable that the recent five decade trend, during the instrumental observing period (1947 to present), is consistent with Bakun’s (1990) observations, but the levels of variation, and sign changes for the previous 80-90 years are far greater.
The lesson here is that no matter what level of sophistication the observing technology, and coverage, it will still require that observations be made for many centuries for there to be much utility of these data in any efforts to make statistically credible projections.
Other sorts of information stimulate far more serious concerns over the recent ocean and atmosphere circulation models, and their utility for projecting credible future climate scenarios (Ellsaesser 1989, Sharp 1990).
In this redrawing of Bakun’s (1990) figure it is clear that there is a consistent positive statistical trend in these five data sets. I have added a few indicators to the original graphic, in which dashed boxes identify common periods of changes. During the period from 1968-69 each of the graphs shows that the upwelling index drops dramatically below the trend line, and then quickly rebounds to very high levels, and declines over the last fifteen or so years, in direct opposition to the statistical trend line for the series. The second box outlines the post 1982-83 ENSO warming event period when at least four of the regions appear to have become erratic, and exhibited extreme excursions about the trend line.
The winter season scalar surface wind speed departures from the long term mean, from the COADS are portrayed for four 30 degree latitude swaths around the globe. The instrumental period is outlined by the dotted box, as in Figure 1, and the trends within the four examples are similar to the one that Bakun found in his upwelling index data, as expected. There are, however, some very notable patterns that this series of graphics show us. First is that the northern latitudes tend to lead the changes in the more southerly latitudes, which likely indicates the relative sea surface to land surface ratios. Second, the long term patterns of change are far more extreme than anything that has been observed during the recent five decades of the instrumental period.
The importance of long-term climate records, and careful integration of ecological responses is well recognized by geologists and enlightened geophysicists (Crowley 1983, 1990).
It is the key to understanding climate change, and credible forecasting. The recent Intergovernmental Panel on Climate Change reports (IPPC 1990) on the potential climate change scenarios accept the basic tenets of "Green House" warming arguments, even though the analogy is imperfect, at best, and simply inappropriate as anything other than a coded statement of a "dread factor" (Glantz, 1990). The Medieval Warming epoch (850-1200AD)and the Little Ice Age (1450-1780AD) provide examples of extremes in climate within only the last millennia. The fact that the Little Ice Age ended only about 1780 or so provides the backdrop for the warming trend over the recent two centuries. In fact, the greatest warming of this century occurred in the period from the 1920s through about 1940, and if anything, the northern hemisphere temperature was been in decline from about 1945 until about 1972, at which many changes were experienced around the globe (c.f., Figures 3 to 5).
Subtraction of the northern hemisphere Atlantic basin means from the southern hemisphere basin means shows that there have been very strong differences in surface heat budgets for the two Atlantic basins. Compare this and Figure 2 with Figure 4 which is the result of similarly treated, but globally averaged information.
Subtraction of the mean global hemispheric sea surface temperatures, as provided by the U.K. Meteorological Office, yields insight into the interpretation problems related to comparisons of regional and global patterns. Note that the departures (anomaly) about the long-term mean do not have either the same patterns or trends during the record period, particularly from the mid 1940s to present as the Atlantic records for the instrumental period.
From the early 1950s the North Atlantic SST went through a marked decline until 1974, when it began rising back to the long-term mean. The South Atlantic has been experiencing a positive trend, although the SST only rose above small oscillations about the long-term mean since the late 1970s. The north Atlantic basin was warm relative to the southern Atlantic basin for most of the period from 1947 to 1968. For the two recent decades, however, this trend reversed and reached a maximum difference in 1972 (see Figure 3) when the south Atlantic SST was still warmer, a trend which persists.
These figures exemplify the problems in defining any meaningful trends within these spatially disparate processes.
Clearly a macroscope-microscope approach is needed, along with abundant care for not over-valuing one sort of signal over others. Recent work by Gray (1990), relating Sahel rainfall and Atlantic Hurricane activity (Figure 6) and studies of west Africa’s pelagic fishery systems reported by Belveze and Erzini (1984) and Freon (1984) show that there was indeed a common period of climatic shift, the consequences of which reverberated throughout the marine environment, through the pelagic fisheries, and into the local and global economies.
Also notable from these examples is that the recent shift in the climate cycle identified by Gray (1990 – c.f. Figure 6) portends great responses, and another ecological shift in the region, as the rainfall increases in the African interior.
It should also be noted here, that from earlier studies of the patterns of variation of eastern boundary current pelagic fisheries, longer term patterns of variation are clearly recorded, in epochs lasting for about 350 years in the California Current (Soutar and Isaacs 1969, 1974, Soutar and Crill, 1977) and (Baumgartner et al. 1984, 1989,). Figure 7 summarizes the scale flux estimates from studies of sediments in the Santa Barbara Basin, off southern California. Similar laminated sediments from the Benguela Current region, within Walvis Bay, show a shorter term, twenty-thirty year pattern of variation (Shackleton, 1987). This appears to be a result of the forcing from both the South Atlantic and Indian Oceans.
These plots from Gray (1990) show the relationships between rainfall in the Sahel (lower graph) and the amount of hurricane activity related to the anomaly (index) of that rainfall (upper graph). Note that I although have not "boxed" the critical periods for the three studies, that the major transition periods correspond with the Bakun data.
Studies of the Moroccan and Senegalese pelagic fisheries showed that these fisheries were very subject to climate forcing (Belveze and Erzini 1984, and Freon 1984), as are all other fisheries contexts, as far as I can discern.
The situation of an island community is that there is no way to adapt to the great shifts in ecological scale processes, other than through innovation, or emigration. The recent declines in the Moroccan, the Chilean and the Japanese sardine resources portend great economic upheavals. The Japanese will suffer great duress, in cultural terms, since their fish culture industry will have to find another source of protein feed, or their industry will collapse. The Chilean industry will have to cope with the northward collapse of the sardine and hope that they might benefit from greater upwelling related anchoveta blooms. The options for Morocco are fewer.
The Annual varve sediment records of the Santa Barbara Basin have been sorted and fish debris (e.g., scales, otoliths, hard parts) identified, and enumerated for contiguous segments for the recent two thousand year period (provided by Dr. Andrew Soutar. SIO, La Jolla, CA.). These records have been the inspiration for much speculation about the periodic ebb and flow of pelagic species, and the climatic regimes that dominated each period. Similar records from dysaerobic sediments from Walvis Bay and from Peru record similar patterns of population responses to climate-driven ocean changes.
Other patterns which emerge from these two sets of time series, one extending, again, only from the onset of the instrumental period, and the other over 2000 years.
Avaria (1985) provided the basic study from which the updated Figure 8 was produced. These data imply that not only were the fishery species patterns changed in the western South American pelagic fisheries, but the biomass production center shifted over time, to the south, again beginning in about 1968-69. The trend then reversed, following the 1982-83 El Niño-Southern Oscillation (ENSO) warm event.
Avaria (1985) provided the original example of the shift in pelagic fish production off western South America, from fishery catch statistics. These have been updated through 1986, from FAO files, and the recent few years unofficial landings data confirm that the shift in the ecological situation from 1968 to 1983-84 has reversed, and another epoch of anchoveta dominance has begun. Peruvian fisheries landed over 6 million tons of anchoveta in 1990, for the first time since the early 1970s.
Chilean sardine catches are in decline, and the population is moving northward and offshore. These two periods correspond with those of the previously described ocean/atmosphere and ecological data sets. Clearly, management under single species sustained yield concepts is simply inappropriate, and counter productive.
Economic Factors, Society’s Engine
I do not wish to over burden this discussion with a lot of anecdotes from the last decades experiences with the price of petroleum products other than to state that since the mid 1970s, there have been few or no high seas tuna vessels that have paid their own way. That is to say that the economically viable vessels have been paid for in advance, by the profits of the previous era of high investment yields under a low relative fuel cost and higher product value regime. The global petroleum scenario is well understood, by most everyone, yet the second part of the equation has only a few followers.
The price of processing fish has actually decreased in the last decade, as the processing centers moved from the New World to Asia.
Thailand’s recent rise from a non-producer and zero canned tuna production, to the foremost exporter of canned tuna in the world has also followed the shift of the catches by high seas seine fleets from the eastern Pacific and eastern Atlantic to the Indian Ocean and western Pacific Ocean. This shift in geography is the single most important factor that promoted the present availability of canned tuna products and allowed the overall decline of prices which in the Americas are well below historical levels. The unparallelled rises in costs of sugar and vegetable oil based processed dressings which are required for the tuna salad has certainly been a more important factor in the cost of a lunch than has the tuna.
Joseph Schumpeter (1951), the noteworthy Viennese economist, posed the thesis that innovation was the engine behind economic cycles.
It is also a truism that "necessity is the mother of invention.", and I would like to connect these two concepts into a single principle, which can be stated as follows: Necessity stimulates innovation, which fuels economies. From which it follows that if that need is driven by changes in climate, then economic cycles will follow climatic cycles.
This is an empirical truth, as is written in the history of cultures around the world.
That climate changes on all time and space scales is also a truism, but the major consideration is that of the changes in seasonal patterns, with an eye on the major climate events. The longer term climate changes are notably those affecting seasonal patterns, while the year to year variations may actually exceed these mean changes in pattern. Yet it is the day to day, season to season changes that fish respond to, and which determine the societal responses and opportunities. River flow and flood records (Figure 9) impart this message for many regions of the world, in this case for Arizona.
Webb and colleagues (Hjalmarson, 1990, Webb and Betancourt, 1990) have compiled records from several drainage basins, and collated the peak discharge rates by season and year so that the various components of the seasonal cycle and atmospheric states might be inferred. There is clearly a centennial scale pattern of extreme events within these records, which signal the time scales of the north-south oscillations of the Inter-Tropical Convergence Zone (the seasonally varying atmospheric equator).
Jorge Csirke and I wrote in our introduction to the Proceedings of the 1983 Expert Consultation on the Changes in Abundance and Species Composition of Neritic Fish Populations that "fisheries science would have a different history if the North Sea were subject to frequent El Niños". Instead, the North Atlantic is subject to patterns of variation that are on the order of life times, 40-50 years which in itself allows each side of any argument over fishing versus nature to be right for half a career. Cushing (1986) summarized Southward (1974a,b) and Southward et al. (1975) net-sampling studies of the long-term changes in biota of the English Channel, in which sardine eggs were counted and compared to arrow worm, (Sagitta spp.) numbers. The two species have distinctly different habitat requirements, the sardine prefers warmer ocean regimes than does Sagitta, a major planktivorous predator. The period of the apparent eastern Atlantic ocean cycles (c.f., Wyatt and Larañetta 1988) is just about half that of the river flow rate records from the Southwest of North America, and about twice that of the sardine scale count records from Walvis Bay sediments, as reported by Shackleton (1987).
The debates that the vociferous proponents of stability and equilibrium based population dynamics theory have generated over the last four decades can be negated in an instant, simply by following the catch variations and species changes for any one, or all low latitude fisheries since the mid 1960s, to present.
Surely one root of the stock management problem is all too obvious. In spite of the long records of population variations, with or without fishing, it remains unlikely that you will find any ocean fishery that is managed under a strategy that uses available synoptic information on local or regional environmental variability.
Yet – if you ask the "standard" fisherman what he uses as a cue for when to go fishing – he will nearly always describe a "standard" environmentally based cue in response.
These and other available fishery related records provide more than enough reason to rethink the basis for management of ocean fish resources.
These conclusions are neither new nor radical, as this was the conclusion in the Reports from the Proceedings of the 1983 FAO Expert Consultation on Changes in Abundance and Species Composition of Neritic Fish Resources, held in San Jose, Costa Rica (Sharp and Csirke (1984). What is new, is that it is now possible to tie the changes on both terrestrial and ocean environments to an atmospheric process, that is totally out of the control of man, although some fear that we may be affecting the long-term trend. Given that climate changes continuously, with shorter and longer term trends about several time scales of patterns, perhaps it would be wiser to include more environmental analysis in management plans, and decision making, rather than to adhere blindly to rather inappropriate models that assume stability and relative equilibrium conditions. Models operating without concern for natural climate trends and cycles (i.e., under the assumption of long term sustainability) cannot but be misleading and actually cause economic over-exploitation, when that is neither desirable nor likely to be borne out in time. The problems of fisheries management cannot be resolved until fisheries management evolves past these assumptions, and like the climate modeling efforts, include sufficient information and interactions that they can be useful in projections.
Seasonality is the strongest climate signal on the planet, and all climate change will result in changes in the basic seasonal patterns, region by region, forming a grand shifting mosaic in time and space (Ropelewski and Halpert (1988).
In line with the original thesis of my presentation, it appears that island populations are highly adaptable, in contrast to coastal or terrestrial ones. This is simply because the islanders have learned to expect change, and to cope with the changing opportunities, as they present themselves, or they disappear. The riches of the Azores derive from the rather strong seasonality of the ocean environment, and the fact that the transitional characteristics of the locale is a bonus in that it provides for the richness of opportunities afforded by the movements of oceanic resources across the region. The fact that there is sufficient temperate neritic province surrounding the islands provides for an indigenous ecological system that has provided the bounty that sustains the Azorean population through short periods when the open ocean does not provide.
A word of caution is due here.
I have not suggested that anyone throw their good senses to the winds, so to speak, and overindulge, harvesting the seas to a point where the ecological balances are perturbed, and species are threatened, or even to the point where the economics of each fishery becomes marginal. That is what equilibrium theory and endless market growth economic theory applied in a varying environment will produce, without fail. What I am suggesting is that, like any predator, a fishery that cannot track changes in its prey, and shift with the changing patterns of opportunities, is doomed. Prevention of this pattern is quite simple.
We must never forget that climate change is a fact of life, and an important source of ecological vigor.
Although these changes can be difficult, they are necessary for many life-giving functions and the sustained survival of us all.
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