scholarly journals Historical fluctuations and recent observations of Northern Anchovy Engraulis mordax in the Salish Sea

2019 ◽  
Vol 159 ◽  
pp. 22-41 ◽  
Author(s):  
William D.P. Duguid ◽  
Jennifer L. Boldt ◽  
Lia Chalifour ◽  
Correigh M. Greene ◽  
Moira Galbraith ◽  
...  
Keyword(s):  
Salish Sea ◽  
Northern Anchovy ◽  
Engraulis Mordax

Contribution of Early Life Stages to Interannual Variability in Recruitment of Northern Anchovy (Engraulis mordax)

1988 ◽  
Vol 45 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Randall M. Peterman ◽  
Michael J. Bradford ◽  
Nancy C. H. Lo ◽  
Richard D. Methot
Keyword(s):  
Interannual Variability ◽  
Early Life ◽  
Estimation Error ◽  
Life Stage ◽  
Early Life Stage ◽  
Large Variability ◽  
Three Stages ◽  
Northern Anchovy ◽  
Engraulis Mordax ◽  
Eggs And Larvae

We tested Hjort's and Lasker's hypotheses that the abundance of recruits in fishes is determined at an early life stage. Using 13 yr of data on components of population dynamics of the well-studied northern anchovy (Engraulis mordax), we reconstructed the abundance of anchovy in each year at three stages: eggs, 4.5-d-old yolk-sac larvae, and 19-d-old larvae. No abundance measure was significantly correlated with age 1 recruits, resulting in rejection of Hjort's and Lasker's hypotheses. We give reasons why the low correlations are not an artifact of estimation error. The lack of correlation exists because of the large variability (CV = 171%) in survival rate between age 19 d and age 1 yr. Therefore, attempts to understand interannual variability in recruitment in this, and perhaps other, marine fish species may have to rely not only on data on eggs and larvae, but especially on data on abundances estimated after 20 d, closer to the age at recruitment.

Indices of Relative Abundance from Fish Spotter Data based on Delta-Lognornial Models

1992 ◽  
Vol 49 (12) ◽  
pp. 2515-2526 ◽  
Author(s):  
N. Chyan-huei Lo ◽  
Larry D. Jacobson ◽  
James L. Squire
Keyword(s):  
Relative Abundance ◽  
Mixed Layer Depth ◽  
Cost Effective ◽  
Time Of Day ◽  
Environmental Data ◽  
Layer Depth ◽  
Data Simulation ◽  
Fish Schools ◽  
Northern Anchovy ◽  
Engraulis Mordax

Fish spotters are pilots in small aircraft employed by commercial fishermen to locate, identify, estimate the size of, and direct boats toward pelagic fish schools. Data describing species, location, and size of schools can be inexpensively obtained from fish spotters but are difficult to interpret statistically. We developed an index of relative abundance from fish spotter data based on extended delta-lognormal models and applied the method to data for northern anchovy (Engraulis mordax). In contrast with previous approaches, our method used all available data, provided an index for northern anchovy that was proportional to abundance, and explicitly modeled factors (pilots, regions, seasons, and time of day) that affected observations by fish spotters. We also included information about mixed layer depth and sea surface temperature in models for a reduced study area and found that environmental data, where available, can be used to improve estimates of relative abundance from fish spotter data. Simulation results indicated that our approach is a cost-effective way to improve biomass estimates for pelagic species like northern anchovy.

Mortality and Recruitment of Pacific Sardine, Sardinops sagax caerulea, Larvae in the California Current

1991 ◽  
Vol 48 (9) ◽  
pp. 1713-1723 ◽  
Author(s):  
John L. Butler
Keyword(s):  
Larval Mortality ◽  
Mortality Rates ◽  
Larval Transport ◽  
Water Column Stability ◽  
Recruitment Success ◽  
Pacific Sardine ◽  
Pacific Mackerel ◽  
Sardinops Sagax ◽  
Northern Anchovy ◽  
Engraulis Mordax

The mortality rates of Pacific sardine, Sardinops sagax caerulea, larvae (< 20 d) increased during 1951–67, and this increase was positively correlated with the increase in biomass of northern anchovy, Engraulis mordax. Other potential correlates with larval sardine mortality rates were examined using multiple correlation. These included temperature and zooplankton volumes at stations positive for sardine larvae, water column stability, upwelling, transport, salinity anomalies, and Pacific mackerel, Scomber japonicus, abundance. None contributed significantly to the multiple regression with anchovy abundance. Thus, no evidence existed for either Lasker's stable ocean hypothesis of larval mortality or Hjort's larval transport hypothesis. The logarithm of the ratio of sardine recruits at age 2 to the spawning biomass was used as an index of recruitment success. Sardine recruitment success at age 2 was not correlated with larval mortality rates. Sardine recruitment, however, was negatively correlated with both northern anchovy biomass and the combined biomass of Pacific sardine, Pacific mackerel, and northern anchovy. A plausible explanation for this result is that predation by pelagic fishes results in greater mortality rates of sardine larvae and juveniles which in turn decrease sardine recruitment.

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