Contrasting environmental drivers of adult and juvenile growth in a marine fish: implications for the effects of climate change

Abstract

Many marine fishes have life history strategies that involve ontogenetic changes in the use of coastal habitats. Such ontogenetic shifts may place these species at particular risk from climate change, because the successive environments they inhabit can differ in the type, frequency and severity of changes related to global warming. We used a dendrochronology approach to examine the physical and biological drivers of growth of adult and juvenile mangrove jack (Lutjanus argentimaculatus) from tropical north-western Australia. Juveniles of this species inhabit estuarine environments and adults reside on coastal reefs. The Niño-4 index, a measure of the status of the El Niño-Southern Oscillation (ENSO) had the highest correlation with adult growth chronologies, with La Niña years (characterised by warmer temperatures and lower salinities) having positive impacts on growth. Atmospheric and oceanographic phenomena operating at ocean-basin scales seem to be important correlates of the processes driving growth in local coastal habitats. Conversely, terrestrial factors influencing precipitation and river runoff were positively correlated with the growth of juveniles in estuaries. Our results show that the impacts of climate change on these two life history stages are likely to be different, with implications for resilience and management of populations.

Figure 1. Pearson’s correlation coefficients between Lutjanus argentimaculatus chronologies and January to March values of significantly correlated environmental variables:

(a) adult chronology from 1975 to 2003 with the Niño-4 index (Niño-4), Sea Surface Salinity (SSS) and Pacific Decadal Oscillation (PDO) and (b) juvenile chronology from 1965 to 1978 with PDO and rainfall. Asterisks represent p-values of the Pearson’s correlation test, with p < 0.01 (***), p < 0.03 (**) and p < 0.04 (*).

Figure 2. Relationships between Lutjanus argentimaculatus chronologies and environmental variables included in the linear models:

(a) adult chronology from 1975 to 2003 plotted with Principal Component 1 (PC1), which accounted for 60% of the variation for January to March values of the Niño-4 index (Niño-4), Sea Surface Salinity (SSS) and Pacific Decadal Oscillation (PDO); (b) regression plot of adult chronology with PC1; (c) juvenile chronology from 1965 to 1978 with February PDO index; (d) regression plot of juvenile chronology with February PDO index; (e) juvenile chronology from 1965 to 1978 with February rainfall (mm month^-1); and (f) regression plot of juvenile chronology with fourth root transformed February rainfall values.

Figure 3. Map of spatial correlations of adult Lutjanus argentimaculatus chronology with ocean heat content.

January ocean heat content (0–750 m depth) from Simple Ocean Data Assimilation (SODA) reanalysis of ocean climate variability was correlated with the adult mangrove jack chronology from 1975 to 2003. Warmer colours indicate positive correlations, cooler colours indicate negative correlations. Map was obtained and modified from KNMI Climate Explorer, a web application for climate data, using our data and ocean heat content.

Figure 4. Map of sampling sites in north-western Australia.

Lutjanus argentimaculatus were captured from various offshore sampling areas by research trapping, commercial trapping or commercial fish trawls from 1996 to 2005. Points on the map show general locations of capture and the map was created using the package “mapdata” in R software.

Figure 5. Photomicrographs of the dorsal side of a Lutjanus argentimaculatus otolith section:

(a) the dorsal section of the otolith was chosen for consistently clear annual increments and (b) a close up image of the same otolith with transect line and increments labelled with corresponding calendar years.