Cycles, trends, and residual variation in the Iberian sardine (Sardina pilchardus) recruitment series and their relationship with the environment

Abstract Santos, M. B., González-Quirós, R., Riveiro, I., Cabanas, J. M., Porteiro, C., and Pierce, G. J. 2012. Cycles, trends, and residual variation in the Iberian sardine (Sardina pilchardus) recruitment series and their relationship with the environment. – ICES Journal of Marine Science, 69: 739–750. Recruitment variability is an important component of the dynamics of Iberian sardine (Sardine pilchardus). Since 2006, poor recruitment has led to a decrease in stock biomass, the latest in a series of such crises for sardine fisheries. Understanding the mechanisms behind recruitment fluctuations has been the objective of many previous studies, and various relationships between recruitment and environmental variables have been proposed. However, such studies face several analytical challenges, including short time-series and autocorrelated data. A new analysis of empirical relationships with environmental series is presented, using statistical methods designed to cope with these issues, including dynamic factor analysis, generalized additive models, and mixed models. Relationships are identified between recruitment and global (number of sunspots), regional (NAOAutumn), and local [winter wind strength, sea surface temperature (SST), and upwelling] environmental variables. Separating these series into trend and noise components permitted further investigation of the nature of the relationships. Whereas the other three environmental variables were related to the trend in recruitment, SST was related to residual variation around the trend, providing stronger evidence for a causal link, possible mechanisms for which are discussed. After the removal of trend and cyclic components, residual variation in recruitment is also weakly related to the previous year's spawning-stock biomass.

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Spatiotemporal modelling for the annual egg production method of stock assessment using generalized additive models

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f98-143 ◽

1998 ◽

Vol 55 (12) ◽

pp. 2608-2621 ◽

Cited By ~ 23

Author(s):

N H Augustin ◽

D L Borchers ◽

E D Clarke ◽

S T Buckland ◽

M Walsh

Keyword(s):

Environmental Variables ◽

Egg Production ◽

Survey Design ◽

Stock Assessment ◽

Generalized Additive Models ◽

Production Method ◽

Additive Models ◽

Atlantic Mackerel ◽

Egg Density ◽

Survey Designs

Generalized additive models (GAMs) are used to model the spatiotemporal distribution of egg density as a function of locational and environmental variables. The main aim of using GAMs is to improve precision of egg abundance estimates needed for the annual egg production method. The application of GAMs requires a survey design with good coverage in space and time. If the only results available are from less optimal survey designs, they can be improved by using historical data for spawning boundaries. The method is applied to plankton egg survey data of Atlantic mackerel (Scomber scombrus) in 1995. The GAM-based method improves the precision of estimates substantially and is also useful in explaining complex space-time trends using environmental variables.

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On the dynamics of Sardina pilchardus: orbits of stability and environmental forcing

ICES Journal of Marine Science ◽

10.1093/icesjms/fsq107 ◽

2010 ◽

Vol 67 (8) ◽

pp. 1565-1573

Author(s):

A. P. Solari ◽

M. T. G. Santamaría ◽

M. F. Borges ◽

A. M. P. Santos ◽

H. Mendes ◽

...

Keyword(s):

Sea Surface ◽

External Forcing ◽

Fishing Mortality ◽

Sardina Pilchardus ◽

Environmental Forcing ◽

Stock Biomass ◽

External Variables ◽

Multiresolution Decomposition ◽

Spawning Stock ◽

Upwelling Index

Abstract Solari, A. P., Santamaría, M. T. G., Borges, M. F., Santos, A. M. P., Mendes, H., Balguerías, E., Díaz Cordero, J. A., Castro, J. J., and Bas, C. 2010. On the dynamics of Sardina pilchardus: orbits of stability and environmental forcing. – ICES Journal of Marine Science, 67: 1565–1573. The dynamics of Sardina pilchardus in Iberian upwelling are examined. Spawning-stock biomass (SSB), recruitment (R), and production (R/SSB) data for the years 1978–2006 are analysed in relation to the upwelling index (UPW) and sea surface temperature (SST). The population oscillates in two relatively stable orbits (identified by multiresolution decomposition of the recruitment series) because the external forcing (UPW and SST) are the inverse of each other and the synchrony is lost between the two external variables, R and R/SSB as they shift towards steep, negative (depensatory) trends. Such mechanics may have induced recruitment failures and significant decreases in abundance of Iberian sardine. The relationships are assumed to validate a complex and dynamic continuum (multiple orbits of stability) and an alternative variable-carrying-capacity population model. Radial systems with two orbits of stability are proposed for the R/SSB and S/SSB (where S is the stock size) relationships. Results are discussed in relation to classical and alternative SR models to address stock rehabilitation and fishing mortality issues as the population shifts towards low recruitment and abundance, and critical factors to consider in developing exploitation strategies for systems with multiple orbits of stability are discussed.

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Investigating the use of proxies for fecundity to improve management advice for western horse mackerel Trachurus trachurus

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2005.07.006 ◽

2006 ◽

Vol 63 (1) ◽

pp. 25-35 ◽

Cited By ~ 21

Author(s):

J.A.A. De Oliveira ◽

B.A. Roel ◽

M. Dickey-Collas

Keyword(s):

Egg Production ◽

Stock Assessment ◽

Biological Indicators ◽

Horse Mackerel ◽

Feeding Intensity ◽

Short Time Series ◽

Stock Biomass ◽

Spawning Stock ◽

Management Advice ◽

Short Time

Abstract Observations of fecundity from the 2001 western horse mackerel spawning-stock biomass survey suggest that the species is an indeterminate spawner. Therefore, estimates of fecundity based on biological analyses and until recently used in the calibration of the stock assessment are now questioned. The stock is assessed by fitting a linked Separable and ADAPT VPA-based model to the catch-at-age data and to the egg production estimates. Currently, the assumption is that egg production and spawning-stock biomass are linked by a constant but unknown fecundity parameter, estimated within the model. In this study, the effects of introducing relationships linking biological indicators of fecundity, such as lipid content or feeding intensity during the spawning season, to actual fecundity are examined within a simulation framework. Simulations suggest that when the underlying relationships between fecundity and the proxy are poorly described, weak, or based on a relatively short time-series of data, the assumption of constant fecundity will result in better management advice than using the proxy.

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Performance of harvest control rules in a variable environment

ICES Journal of Marine Science ◽

10.1093/icesjms/fsp297 ◽

2010 ◽

Vol 67 (5) ◽

pp. 1051-1062 ◽

Cited By ~ 18

Author(s):

Thomas Brunel ◽

Gerjan J. Piet ◽

Ralf van Hal ◽

Christine Röckmann

Keyword(s):

Dynamic Models ◽

Generalized Additive Models ◽

Maximum Sustainable Yield ◽

Additive Models ◽

Precautionary Approach ◽

Variable Environment ◽

Control Rules ◽

Stock Biomass ◽

Stock Recruitment ◽

Harvest Control Rules

AbstractBrunel, T., Piet, G. J., van Hal, R., and Röckmann, C. 2010. Performance of harvest control rules in a variable environment. – ICES Journal of Marine Science, 67: 1051–1062. Population dynamic models used for fisheries management assume that stocks are isolated entities, ignoring the influence of environmental factors on stock productivity. An operating model parameterized for North Sea cod, plaice, and herring is developed, in which the link between recruitment and environment is assumed to be known and described by generalized additive models. This tool is used to compare the performance of harvest control rules (HCRs) when recruitment is independent of the environment or when recruitment is affected by an environment varying according to different scenarios. The first HCR exploited the stock with a fixed fishing mortality (F) corresponding to maximum sustainable yield, and in the second HCR, F was set equal to the precautionary approach F (i.e. Fpa), but reduced from Fpa when stock biomass fell below Bpa. The performance of the HCRs altered only slightly in a randomly varying environment compared with a constant one. For a detrimental change in the environment, however, no HCR could prevent a massive decrease in stock size. The performance of the HCRs was also influenced by the stock characteristics, such as recruitment variability or the shape of the stock–recruitment relationship. The performance of “environmental” HCRs (eHCRs), in which F varies depending on environmental conditions, was compared with that of conventional HCRs. The gain in using the eHCR was small, except for a detrimental change in the environment, where the eHCR performed markedly better than a conventional HCR. The benefits of using the eHCR were the greatest for the stock with the strongest environment–recruitment relationship.

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Spawning stock biomass modulation of environment - recruitment relationship in a marginal spring spawning herring (Clupea harengus membras) population

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2021-0018 ◽

2021 ◽

Author(s):

Henn Ojaveer ◽

Riina Klais-Peets ◽

Heli Einberg ◽

Gunta Rubene

Keyword(s):

Environmental Variables ◽

Time Span ◽

Clupea Harengus ◽

Fish Recruitment ◽

Linear Relationships ◽

Stock Biomass ◽

Abrupt Changes ◽

Non Linear ◽

Spawning Stock ◽

Gulf Of Riga

Scientific interest in the dynamics of fish recruitment dates back to the beginning of the 20th century. Since then, several studies have shown that the environment may have a stronger effect on recruitment (R) compared to that of the spawning stock biomass (SSB). By combining a suite of methods designed to detect the non-linear, non-stationary and interactive relationships, we have re-evaluated the potential drivers and their interactions responsible for the multiannual dynamics of the recruitment dynamics of the Gulf of Riga (Baltic Sea) spring spawning herring population at the longest time-span to date (1958-2015) allowing coverage of variable ecosystem conditions. R was affected significantly by prey density and the severity of the first winter. Although SSB was not a good predictor of R, adding interaction with SSB significantly improved the model, hence the effect of the two environmental variables on R was modulated by SSB. While temporal changes in the environment-R relationship were generally gradual, several abrupt changes were evident in the strength of these relationships. In addition, non-stationary, linear and non-linear relationships were observed.

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Zooplankton abundance trends and patterns in Shelikof Strait, western Gulf of Alaska, USA, 1990–2017

Journal of Plankton Research ◽

10.1093/plankt/fbaa019 ◽

2020 ◽

Vol 42 (3) ◽

pp. 334-354 ◽

Cited By ~ 2

Author(s):

David G Kimmel ◽

Janet T Duffy-Anderson

Keyword(s):

Time Series ◽

Generalized Additive Models ◽

Zooplankton Community ◽

Strong Relationship ◽

Gulf Of Alaska ◽

Additive Models ◽

Environmental Data ◽

Dynamic Factor ◽

Zooplankton Abundance ◽

Underlying Trend

Abstract A multivariate approach was used to analyze spring zooplankton abundance in Shelikof Strait, western Gulf of Alaska. abundance of individual zooplankton taxa was related to environmental variables using generalized additive models. The most important variables that correlated with zooplankton abundance were water temperature, salinity and ordinal day (day of year when sample was collected). A long-term increase in abundance was found for the calanoid copepod Calanus pacificus, copepodite stage 5 (C5). A dynamic factor analysis (DFA) indicated one underlying trend in the multivariate environmental data that related to phases of the Pacific Decadal Oscillation. DFA of zooplankton time series also indicated one underlying trend where the positive phase was characterized by increases in the abundance of C. marshallae C5, C. pacificus C5, Eucalanus bungii C4, Pseudocalanus spp. C5 and Limacina helicina and declines in the abundance of Neocalanus cristatus C4 and Neocalanus spp. C4. The environmental and zooplankton DFA trends were not correlated over the length of the entire time period; however, the two time series were correlated post-2004. The strong relationship between environmental conditions, zooplankton abundance and time of sampling suggests that continued warming in the region may lead to changes in zooplankton community composition and timing of life history events during spring.

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Recruitment of North Sea cod (Gadus morhua) and Norway pout (Trisopterus esmarkii) between 1992 and 2006: the interplay between climate influence and predation

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f09-022 ◽

2009 ◽

Vol 66 (4) ◽

pp. 633-648 ◽

Cited By ~ 18

Author(s):

Alexander Kempf ◽

Jens Floeter ◽

Axel Temming

Keyword(s):

North Sea ◽

Gadus Morhua ◽

Generalized Additive Models ◽

Additive Models ◽

The North ◽

Time Period ◽

Spawning Stock ◽

The Status ◽

Temperature Ranges ◽

The North Sea

The interplay between temperature-related processes and predation in determining age-1 recruitment strength between 1992 and 2006 was analysed for North Sea cod ( Gadus morhua ) and Norway pout ( Trisopterus esmarkii ). For this purpose, an predation impact index (PI) was calculated out of survey data. PI was assumed to depend on the abundance of the predators and on the spatial overlap between predator and prey populations. Generalized additive models (GAMs) were created with spawning stock biomass (SSB) and sea surface temperature (SST) in the respective spawning and nursery areas and PI as explaining variables. SSB had no significant impact on recruitment during this time period for both species. SSTs during spring and PI explained the interannual variability in recruitment strength to a large extent (88% of the total variance for cod and 68% for Norway pout). The SST during spring determined the overall level of recruitment. At SSTs above a certain level, however, the effect on recruitment was no longer significant. In these temperature ranges, predation was the dominant effect. Therefore, the fate of North Sea cod and Norway pout stocks under global-warming conditions will be strongly influenced by the status of the North Sea food web.

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Fecundity variation in Icelandic summer-spawning herring and implications for reproductive potential

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2005.10.002 ◽

2006 ◽

Vol 63 (3) ◽

pp. 493-503 ◽

Cited By ~ 33

Author(s):

Guðmundur J. Óskarsson ◽

Christopher T. Taggart

Keyword(s):

Egg Production ◽

Reproductive Potential ◽

Clupea Harengus ◽

Maturation Stage ◽

Oocyte Diameter ◽

Potential Fecundity ◽

Residual Variation ◽

Stock Biomass ◽

Spawning Stock ◽

Spawning Time

Abstract An exploration of fish fecundity aimed at estimating the reproductive potential of a stock requires comprehensive and quantitative examinations of the influencing factors. Here, Icelandic summer-spawning herring (Clupea harengus) are used to quantify potential fecundity (FP, number of eggs) and relative fecundity [RFP = FP (body weight − ovary weight)−1] as functions of length (L) and weight (W) in mature prespawning herring. Using a coupled examination of atresia (oocyte degeneration in the ovary) and the maturation stage of oocytes as characterized by size, we show that atresia has no meaningful effect on fecundity estimates if determined near the spawning time. Among prespawning herring, FP is a strong function of L or W (r2 = 0.84 in either case). Fulton's condition factor K (=100WL−3) explains a trivial (1.5%) but significant (p < 0.0001) amount of the residual variation in FP, and appears to have the greatest effect among smaller length classes. RFP is also a function of L (r2 = 0.56), and oocyte diameter explains 36% of the residual variation (p < 0.001). Therefore, stock-specific total egg production in herring can diverge from the assumed proportionality between total egg production and spawning-stock biomass through variations in the length structure of the stock, and to a lesser extent through the condition of prespawning herring.

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