Length conversions and mass–length relationships of five forage‐fish species in the California current ecosystem

Abstract

Length‐measurement conversions and seasonal mass–length relationships (MLR) for Pacific herring Clupea pallasii, northern anchovy Engraulis mordax, Pacific sardine Sardinops sagax, Pacific mackerel Scomber japonicus and jack mackerel Trachurus symmetricus in the California Current are presented. The conversions between total (LT), fork (LF,) and standard lengths (LS) should facilitate comparisons of data across disciplines and institutions. These equations resulted from an analysis of measurements spanning 14 years and the western seaboard of North America, from the north end of Vancouver Island to the USA–Mexico border. Major‐axis regressions were used to calculate reciprocal length‐measurement conversions (e.g., LT to LS and LS to LT) and generalised linear models and ordinary least‐squares models were used to create MLRs that account for seasonal variations. The MLR models indicated seasonal differences for all species except C. pallasii, for which there was no multi‐season data. Discrepancies between these and published models were examined, along with the suitability and benefit of the various types of models used for length‐measurement conversion and MLRs.

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality

“…The results of this study provide an update of the understanding of CSNA growth patterns, given that the last work examining growth of the CSNA through the adult stage was completed 38 years ago (i.e., Parrish et al, 1985). We found patterns in somatic growth of the CSNA that are typical of rselected and opportunistic species, which have small body sizes, low maximum ages, and high growth rates (Adams, 1980;Winemiller and Rose, 1992;King and McFarlane, 2003).…”

“…Seasonal growth oscillations have been reported for other engraulids (Palomares et al, 1987;Cubillos and Arancibia, 1993;Bellido et al, 2000;Bilgin et al, 2013;Cerna and Plaza, 2016). Northern anchovy reportedly live up to 8 years (Mallicoate and Parrish, 1981), but older individuals (i.e., age-4+ fish) are thought to be relatively scarce (Collins, 1969;Spratt, 1975;Mallicoate and Parrish, 1981;Parrish et al, 1985). Understanding the age structure and growth patterns of northern anchovy is important, as it is a model species for examining and projecting the effects of climate change on clupeoids and marine communities in the CCE and on fisheries management (Muhling et al, 2019(Muhling et al, , 2020Tommasi et al, 2021).…”

“…No recent work has included examination of somatic growth of the CSNA, despite its ecological role in the CCE and the importance of growth estimates in informing stock assessments. The most recent work examining growth of northern anchovy through the adult stage was done by Parrish et al (1985), and a few limited studies have provided values of growth parameters (i.e., mean asymptotic length [L ∞ ] and the growth coefficient [K]) calculated by using traditional growth models (Spratt, 1975;Cisneros et al, 1990). In no work have seasonal growth oscillations of northern anchovy been modeled by using traditional growth models (e.g., the VBGF) with data on fish collected year-round, but seasonal variations in growth of northern anchovy have been generally observed (Mallicoate and Parrish, 1981;Methot, 1983;Parrish et al, 1985;Butler, 1989;Takahashi et al, 2012).…”

“…The most recent work examining growth of northern anchovy through the adult stage was done by Parrish et al (1985), and a few limited studies have provided values of growth parameters (i.e., mean asymptotic length [L ∞ ] and the growth coefficient [K]) calculated by using traditional growth models (Spratt, 1975;Cisneros et al, 1990). In no work have seasonal growth oscillations of northern anchovy been modeled by using traditional growth models (e.g., the VBGF) with data on fish collected year-round, but seasonal variations in growth of northern anchovy have been generally observed (Mallicoate and Parrish, 1981;Methot, 1983;Parrish et al, 1985;Butler, 1989;Takahashi et al, 2012). Seasonal growth oscillations have been reported for other engraulids (Palomares et al, 1987;Cubillos and Arancibia, 1993;Bellido et al, 2000;Bilgin et al, 2013;Cerna and Plaza, 2016).…”

“…We fit a generalized linear model (GLM) incorporating season for all individuals measured for length and weight (sample size [n]=19,209) to examine the weight-length relationship of the CSNA, similar to the work done by Palance et al (2019). The GLM was fitted by using the base function glm in R (vers.…”