Age and Growth of Pacific Sardine Age and Growth of Pacific Sardine in California During a Period of in California During a Period of

Stock Recovery and Stock Recovery and Geographical ExpansionGeographical Expansion

ByEmmanis DorvalJenny McDaniel

Southwest Fisheries Science CenterDianna Porzio

California Department of Fish and Game

Pacific Pacific SardineSardineSardinop Sardinop

sagaxsagax

BackgroundBackgroundPatterns of individual fish growth rate

• After population decline:o Following low population level due to exploitation

(or to other events), individual fish growth rate is expected to increase (Le Cren et al. 1972, Botsford 1981).

o Following low population level, individual fish growth rate may be several times higher than normal growth rate (i.e., pre-decline or pre-exploitation level ), Le Cren et al. (1972).

BackgroundBackgroundPatterns of individual fish growth rate

•After population rebuilding: o Individual fish growth rate is generally expected

to decline toward normal growth rate (i.e., pre-decline or pre-exploitation level ).

o However, the extent of this decline may depend on the strength of regulating factors that are in play; and/or on how much the environment/habitat of this species been modified compared to pre-decline or pre-exploitation level.

BackgroundBackgroundPatterns of individual sardine growth rate

• In the historical fishery (1937-1957):o Length-at-first annulus formation: 101 – 131 mm (Marr 1960)

•During the recovery of the stock (1990s – 2000s)o Butler et al. (1996)o Hill et al. (2007, 2009, 2011)

BackgroundBackgroundPatterns of individual sardine

growth rateP. sardine growth curve

Butler et (1996)•Fish sampleso Daily Egg Production

Method (DEPM): April - May 1994o Ensenada fishery landings

•Von Bertallanfy growth modelo L∞= 205.4 ± 1.6o k= 1.19 ± 0.04o t0= 0 (fixed)

•Birthdate: January 1

BackgroundBackgroundPatterns of individual sardine growth rate

P. Sardine growth curveHill et al. (2011)

•Fish sampleso Daily Egg Production

Method (DEPM): April – May:

2004-2010o Ensenada/California fishery

landings: 1993 - 2010o Pacific Northwest fishery

landings: 1999-2009

•Birthdate: July 1

L0.5yr = 114 mm L∞= 242 mmk= 0.364

BackgroundBackground• Sardine growth rate: current issues

o Density -dependent changes in growth rates or reproduction have not been identified nor evaluated (Hill et al. 2011).

o Combining fishery-dependent and fishery-independent data may not be the most reliable way to detect density-dependent.

o A single growth model is derived in stock assessment model and applied to all fisheries (i.e., Ensenada and/or California, Pacific Northwest).

o There are no known aged-fish: it is difficult to estimate age-reading bias and imprecision from multiple readings of otoliths.

Research ObjectivesResearch Objectives• Develop methods to estimate and compare

growth rates in the California spawning stock:

o During the recovery of the stock in California (1980s-1990s).

o During the recovery and expansion of the stock from California into the Pacific Northwest and British Columbia (1990s – present).

• Determine how fish migration and fishing development may affect sardine growth rate in the California spawning stock.

MethodsMethods

MethodsMethods

MethodsMethods

MethodsMethodsAge-1+ sardine biomass

Growth comparison between:

•Year-classes: 1994-2003

•Year-classes: 2004-2008

Preliminary resultsPreliminary resultsButler et al. 1996

Least-squares based model

(Reader best ages)

L∞= 205.4 mmk= 1.19t0= 0 (fixed)

Preliminary resultsPreliminary resultsLeast-squares based model

(Reader best ages)

Mixed -effect model Length ~Age | Reader

L∞=283 mm ± 9k=0.22 ± 0.01t0= -3.54 ± 0.5

L∞= 328 mmk= 0.14t0= -3.13

Preliminary resultsPreliminary resultsMixed effect model

Length ~Age | Reader

Mixed -effect model Length ~ Age | Reader

L∞=263 mm ± 10k=0.26 ± 0.01t0= -3.11± 0.68

L∞=294 mm ± 10k=0.19 ± 0.01t0= -4.66 ± 1.31

SummarySummary

SummarySummary

AcknowledgementAcknowledgement