Climate signals in sardine otoliths from the last 7 decades: can we identify the climate changes and shifts in species' distribution?

Abstract

The planet is warming faster than at any other time in recorded history. Fishes are particularly affected for being key components in aquatic biogeochemical processes, ecosystem structuring, and functioning through food web links. Moreover, fishes' responses impact aquatic ecosystems at all levels of ecological organization, i.e., from individuals to the ecosystems, and consequently, results in uncertain future for both to wild fish diversity as to global fisheries. Directly, the warming could lead to increased growth rates with concomitant changes in size-at-age, and even small gradual changes in fish body size which can have large effects on natural mortality, biomass and catch. The Brazilian sardine have suffered a failure in the process of it sustainable managing who added to the intense fishing effort led the fishery to a stock depletion crisis, with important social and economic reflexes, culminating in a situation without precedents in history of its exploitation. Sardine's biomass interannual oscillations was never clearly decoded, whilst mentioned assumptions of environmental interference. And recently, a widening of its distribution has been noted by scientists. It is not by coincidence but by constant concern about fluctuations in the stock of Brazilian sardines, the historical series of sardine otoliths pertaining of the COSS Brazil has beginning in 1970s, when the ocean passed to absorber 93% of the excess heat from greenhouse gas emissions, the main changer of ecosystems. Therefore, taking advantage of the availability of these data, this study will carry out a detailed multidecadal morphologic (landmarks analysis) and isotopic analysis (´13C and ´18O) of Brazilian sardine otoliths, to identify the species' response to environmental warming, mainly related to its complex biomass variation and its changes in geographic distribution. Determining the current age and updating reproductive parameters can reveal adaptative patterns of the sardine to the environment. (AU)