The islands themselves are located in a transition zone between two 

 biogeographic provinces, Oregonian and Californian; therefore, their 

 terrestrial biota contains features of both provinces. Similarly, the 

 marine environment represents a transition zone between cold tempe- 

 rate and warm temperate/subtropical regions and, therefore, contains 

 representatives of both regions. 



The most important oceanographic features of the SCB are its 

 surface currents and related upwellings. The dominant water flow, 

 called the California Current, is southward, bringing in cold waters 

 from the northeastern North Pacific. When that current reaches Point 

 Conception the direction of flow carries it away from the shore (which 

 below Point Conception tends east to southeast), creating a large gyre 

 or eddy in the SCB. The return flow of that gyre, called the California 

 Countercurrent, transports water from southeast to northwest. These 

 two current systems, as simplistically described here, are affected 

 seasonally by flow northeastward from the warmer Davidson Current. 

 Such interactions of warm and cold currents produce seasonal changes 

 in dominant marine organisms in the SCB. Further, changes in the 

 relative strengths of these currents from year to year produce long- 

 term shifts in dominant forms. In general, however, the cold water 

 currents link marine communities in the SCB to more northerly 

 communities, while the warmer northbound currents link them to 

 more southerly communities. The gyres link conditions in the 

 CINMS with those in the broader area of the SCB and nearby waters 

 farther south. While the dynamics of the above described water 

 movement assure an active flow of nutrients from both directions they 

 also mean a like flow of pollutants, posing a threat to the future 

 stability of the region from pollution in California and nearby Ba)a 

 California. 



Mixing from interaction of currents is supplemented by nutrient 

 rich upwelling. In the SCB most such upwelling occurs from February 

 through August when surface waters, driven away from shore by 

 offshore winds, are replaced by colder, richer waters overturning from 

 beneath. These frequent and thorough mixings of the water masses in 

 the SCB create conditions which support a rich and varied marine 

 fauna year-round. But the perids of maximum upwelling correspond 

 with periods of longest days, when high levels of sunlight create 

 maximum growing conditions for the phytoplankton that are the base 

 of the food chain, ensuring that sprmg and summer are the richest 

 periods. Though cetaceans are present year-round, components of the 

 cetacean fauna in the SCB, and therefore in the CINMS, change 

 seasonally. 



There are at least ;o species of cetaceans known from the eastern 

 North Pacific. With the exception of a handful of species which are 

 strictly arctic/subarctic (bowhead whale, belukha and narwhal) or 

 tropical (Eraser's, spotted and spinner dolphins, and melon-headed and 

 pygmy killer whales ) all are known from lower latitude temperate and 

 subtropical waters of the kind characteristic of the SCB and nearby 

 continental shelf and pelagic areas. A few of those are represented in 

 and near the SCB by infrequent sightings or strandings and cannot, 

 therefore, be considered normal members of the area's marine fauna. 

 But at least 14 species either can be found in the SCB year-round in 

 most years or annually appear in substantial numbers as they migrate 

 into or through the area. 



In considering which cetaceans might be seen within the CINMS 

 at a given time and place one would do well to remember several facts. 

 Cetaceans are not randomly distributed. Species do show preferences 

 for various habitat types for feeding and migmtion. In fact, m discus- 

 sions of cetacean ecology, species are often grouped as riverine/ 

 estuarine, coastal, continental shelf continental slope/transition zone 

 and oceanic forms, in reference to depth, water trae and proximity to 

 shore of the habitat(s) in which they are most often seen. Cetacean 

 distribution is clearly tied to the distribution and movements of their 



principal prey species. Except for periods of voluntary and protracted 

 fasts, such as during long-distance migrations, cetaceans expend the 

 bulk of their energy searching for or maintaining contact with an 

 acceptable food supply. 



Table I. Some common prey items for cetaceans occurring in the SCB. 

 "h = Important; "w" = Also taken; O = Not usually taken; 

 = Do not ordinarily occur, at least in important con- 

 centrations in the SCB or CINMS. 



Major Prey 

 Items 



Species 



anchovies euphausiids 



and/or and 



sardines squid hake herring sauries salmon copepods 



Small Delphinids It 



Med-sized delphinids 



Beaked whales O 



Larger baleen whales w 



• • i!r o o o 



• • o 0*0 



• li- o o o 

 o i:V o • 



Secondarily, cetacean distribution is related to undersea topography, 

 major current patterns and w.iter temperatures as they affect productiv- 

 ity. At present, little is understood about the complex dynamics which 

 drive a species in its choice of habitat. For most species one is best 

 advised to acknowledge the limits of understanding but continue 

 provisionally to refer to them in groups by habitat types. 



The CINMS and the SCB contain at least segments of all the above 

 listed habitats except riverine/estuarine. The deep water zones in the 

 CINMS are mostly intrusions of submarine canyons connecting to 

 abyssal depths. However, the proximity of some other parts of the 

 CINMS's boundaries to water of oceanic depths, particularly near the 

 western and southwestern limits, makes probable the appearance of 

 some pelagic species, at least as occasional vagrants, m or very near the 

 CINMS. A variety of continental slope, continental shelf and coastal 

 forms find w.iters of the SCB and the CINMS much to their liking for 

 longer periods. 



The task of accurately characterizing composition and relative 

 abundance of cetacean species in the SCB and CINMS is compounded 

 by additional factors. First, it must be remembered that m.!ny large 

 cetaceans were exploited in the North Pacific during several episodes 

 of yankee and modern whaling. Levels of depletion and, therefore, 

 rates of recovery differ among species. Right whales, for example, exist 

 as a pitiful vestige of a once abundant population. Overkilling in the 

 19th century and continuing harvests from the beleaguered stocks in 

 the first half of this century left the populationl's ) at such low levels that 

 recovery is not apparent. Even if formerly abundant in a given area, a 

 species so devastated may now appear rare there. Gray whales, on the 

 other hand, have been twice reduced to low levels, once in the igth 

 century by yankee whaling, again the first half of this century during 

 several periods of modern whaling. Even so, the population of gray 

 whales has recovered to, or near, its pre-exploitation stock size, some 

 17,000 animals; so, present use by gray whales of the area may well be 

 comparable to its use during previous periods when it was at or near 

 "carrying capacity". 



Other species, which were also heavily affected by whaling activities, 

 such as blue and humpback whales, appear to be recovering, though 

 there is far from agreement about rates of recovery or long term 

 consequences of recent whaling on those rates of recovery. As popula- 

 tions of the various depleted species do recover, their use of the 

 CINMS and nearby waters can be expected to increase. For the 

 moment, in the absence of any studies prior to exploitation, we can 

 only guess at the levels at which each species will stabilize, how balance 

 will be achieved among sympatric and even competing species, and how 

 increasing human pollution and use of the marine environment and 

 resources throughout each species' range mav affect that recovery and 

 balance. 



