Nearshore Forage Fish Assessment


Along the Pacific coast, a number of species are referred to as forage fish (Table 1) due to their small size as adults and important roles as prey for popular recreational fish such as groundfish and salmon. These species can exhibit strong variability in population size and in some places exhibit signs of demographic stress such as loss of age and spatial structure and low abundance. Some forage fish species spawn in waters of the open ocean and are affected primarily by broad-scale pressures like climate variation and commercial fisheries. In addition, species such as Pacific herring, longfin smelt, and surf smelt – which spawn in coastal habitats such as beaches and aquatic macrophytes and reside primarily in coastal waters – may be sensitive to local habitat alterations such as shoreline hardening, levee construction in estuaries, and dredging or conversion of intertidal and subtidal habitats supporting eelgrass. These nearshore forage fish species support a great extent of local recreational fisheries, and in the case of surf smelt may be recreational fisheries themselves.
 

The current management situation argues for improved assessments of nearshore forage fish stocks and their habitat. Four commercially harvested forage fish species comprise the Coastal Pelagic Species Fisheries Management Plan of the Pacific Fisheries Management Council, and at least two of these species are the subject of regular stock assessments. However, the nearshore-orienting species are not as well-documented, particularly with respect to potential impacts on spawning habitats and other types of habitat alterations. Delta smelt and eulachon have been listed as Threatened under the Endangered Species Act, and at least one stock of Pacific herring has also been proposed for listing.
 

In light of growing concerns about the health of nearshore forage fish stocks, an assessment of the nine species spawning in estuaries and nearshore habitats across California, Oregon, and Washington (Table 1) will be conducted. This assessment will leverage existing efforts by PMEP and national efforts by NFHP to improve the National Estuary and Coastal Assessment. The assessment will focus on current and historical measures of forage fish abundance, and these data will be examined in the context of alterations to estuary and nearshore habitats.
 

The proposed assessment is not a stock assessment per se, as it will not identify current biomass across the Pacific coast and attempt to generate surplus production or other reference points. The outputs of the assessment will be determination of local abundance levels and probability of presence/absence in historical (20-50 years old) and recent datasets (last 10 years). These data will examined in conjunction with habitat data (e.g., amount of wetland area, changes in wetland area) to determine the extent to which habitat modifications influence forage fish presence and abundance. Consequently, these data should provide determinations about what places on the Pacific coast have seen the most dramatic changes in nearshore forage fish numbers. This should inform management by:
 

1) determining whether nearshore habitat actions can in fact ameliorate conditions for forage fish stocks;
 

2) shedding light on how our actions on forage fish may affect recreational fisheries indirectly by changing food supply; and
 

3) helping to prioritize habitat actions that can have the greatest benefits to food supplies of recreational fisheries. 


As such, the analysis should serve as a model for other regions with similar forage fish datasets.


Table 1. Forage fish species of the Pacific Coast.

Species

Scientific name

Spawning habitat

Adult habitat

Fisheries Management Plan

Pacific sardine

Sardinops sagax

Pelagic offshore

Pelagic offshore

Coastal Pelagic Species (CPS)

Pacific mackerel

Scomber japonicus

Pelagic offshore

Pelagic offshore

CPS

Northern Anchovy

Engraulis mordax

Pelagic offshore

Pelagic offshore

CPS

Jack mackerel

Trachurus symmetricus

Pelagic offshore

Pelagic offshore

CPS

Pacific saury

Cololabis saira

Pelagic offshore

Pelagic offshore

None

Jack smelt

Atherinopsis californiensis

 

Nearshore substrate

Nearshore

CPS  ecosystem component

Pacific herring

Clupea pallasii

Nearshore substrate and macrophytes

Nearshore

CPS ecosystem component

Topsmelt

Atherinops affinis

Nearshore substrate

Nearshore and estuaries

None

Pacific sand lance

Ammodytes hexapterus

Nearshore and continental shelf

Nearshore and offshore pelagic, sandy bottoms

None

Surf smelt

Hypomesus pretiosus

Beaches

Nearshore

None

Delta smelt

Hypomesus transpacificus

Estuary and river substrate

Nearshore and estuary

None

Longfin smelt

Spirinchus thaleichthys

River gravel

Nearshore

None

Eulachon

Thaleichthys pacificus

River gravel

Nearshore and offshore

None

Three-spined stickleback

Gasterosteus aculeatus

Nearshore and estuary nests

Nearshore and estuary

None