Figure 1. Demersal Fish Diversity per trawl within the Monterey Bay, Gulf of the Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
Cordell Bank, Gulf of the Farallones and Monterey Bay sanctuaries all lie within the California Current ecosystem, one of only four major eastern boundary currents in the world. Their cold-temperate fish fauna fall within the Oregonian zoogeographic province, which extends from Point Conception (near Santa Barbara, CA) to Southeast Alaska. Occasionally, southern species from the California Province (south of Point Conception) extend their ranges to central and northern California during warm oceanographic events, such as El Niño and the Pacific Decadal Oscillation (PDO).
Along the West Coast of North America, the distribution of marine organisms varies with latitude, generally due to regional changes in water temperature. Fishes that inhabit the continental shelf and upper slope within California have been grouped into four latitudinal regions:
- Northern California
- North-Central California
- South-Central California
- Southern California
In addition to latitudinal changes in fish assemblages, groups can also be defined by depth, since fishes respond to changes in environmental conditions such as light intensity, temperature and oxygen concentration, factors that are depth-dependent. Ocean processes and physical habitat also greatly influence species composition and distribution.
Greenblotched rockfish (<em>Sebastes rosenblatti</em>) photographed by NOAA Fisheries (Santa Cruz) from the Delta submersible.
<em>Sternoptyx obscura</em> (Dusky Hatchetfish; Sternoptychidae) collected during mesopelagic fishes survey aboard NOAA SHIP Bell M. Shimada, at Monterey Canyon (SESA 9), 0-414 meters, May 2015. Identified by Robert N. Lea (CAS) and Erica J. Burton (MBNMS). Scale: Centimeter ruler.
Conservation and Management IssuesThe sanctuaries' fish communities respond to both natural and human-caused environmental stresses. Although these stressors are listed separately below, synergies among them exist and can be devastating to fish populations.
The diverse fisheries in central California are part of the region's rich cultural and economic history. The sanctuaries do not currently manage commercial or recreational fisheries; the Pacific Fishery Management Council and California Department of Fish and Game manage federal and state fisheries, respectively.
Productivity and Oceanographic Conditions
El Niño/Southern Oscillation (ENSO) refers to periodic cycling between anomalously warm (El Niño) and cool (La Niña) ocean water temperatures that spread across the equatorial Pacific Ocean. These temperature anomalies indicate perturbations in the ocean and atmosphere that are manifested over broad scales, including the California Current ecosystem.
Biological effects from an El Niño include decreased primary productivity, which often cascades to recruitment failures of ecologically important fish species, particularly rockfishes. In addition, fish species with tropical affinities that are naturally associated with warm water (e.g., billfishes) appear further north.
Like an ENSO event, the PDO comprises a warm and a cool interval, but over a longer period of time. PDOs are periods of sustained climate conditions associated with shifts in ecosystem production regimes in cycles of about 50 years.
Offshore waters in the region are in relatively good condition, but nearshore coastal areas, harbors, lagoons, estuaries and tributaries show a number of problems, including elevated levels of coliform bacteria, detergents, oils, nitrates, sediments and persistent pesticides. These contaminants can have a variety of biological impacts, including bioaccumulation and reduced recruitment of anadramous species.
MonitoringMonitoring is being conducted in both the Monterey Bay and Cordell Bank sanctuaries. Some of these programs are described below.
- The Influence of Varying Tidal Exchange on the Fish and Crab Assemblages of Elkhorn Slough
- Long-term Monitoring of Groundfishes in the Monterey Bay National Marine Sanctuary
- Trends in Fisheries and Fishery Resources (pdf)
- Mid-Water Trawl Pre-Recruit Survey