A continuous time delay-difference type model(CTDDM) applied to stock assessment of the southern Atlantic albacore Thunnus alalunga

A continuous time delay-difference model(CTDDM) has been established that considers continuous time delays of biological processes.The southern Atlantic albacore(Thunnus alalunga) stock is the one of the commercially important tuna population in the marine world.The age structured production model(ASPM) and the surplus production model(SPM) have already been used to assess the albacore stock.However,the ASPM requires detailed biological information and the SPM lacks the biological realism.In this study,we focus on applying a CTDDM to the southern Atlantic albacore(T.alalunga) species,which provides an alternative method to assess this fishery.It is the first time that CTDDM has been provided for assessing the Atlantic albacore(T.alalunga) fishery.CTDDM obtained the 80%confidence interval of MSY(maximum sustainable yield) of(21 510 t,23 118 t).The catch in 2011(24 100 t) is higher than the MSY values and the relative fishing mortality ratio(F_(2011)/F_(MSY)) is higher than 1.0.The results of CTDDM were analyzed to verify the proposed methodology and provide reference information for the sustainable management of the southern Atlantic albacore stock.The CTDDM treats the recruitment,the growth,and the mortality rates as all varying continuously over time and fills gaps between ASPM and SPM in this stock assessment.

Distinguishing the Regional Atmospheric Controls on Precipitation Isotopic Variability in the Central-Southeast Portion of Brazil

Precipitation isotope ratios(O and H)record the history of water phase transitions and fractionation processes during moisture transport and rainfall formation.Here,we evaluated the isotopic composition of precipitation over the central-southeastern region of Brazil at different timescales.Monthly isotopic compositions were associated with classical effects(rainfall amount,seasonality,and continentality),demonstrating the importance of vapor recirculation processes and different regional atmospheric systems(South American Convergence Zone-SACZ and Cold Fronts-CF).While moisture recycling and regional atmospheric processes may also be observed on a daily timescale,classical effects such as the amount effect were not strongly correlated(δ^(18)O-precipitation rate r≤-0.37).Daily variability revealed specific climatic features,such asδ^(18)O depleted values(~-6‰to-8‰)during the wet season were associated with strong convective activity and large moisture availability.Daily isotopic analysis revealed the role of different moisture sources and transport effects.Isotope ratios combined with d-excess explain how atmospheric recirculation processes interact with convective activity during rainfall formation processes.Our findings provide a new understanding of rainfall sampling timescales and highlight the importance of water isotopes to decipher key hydrometeorological processes in a complex spatial and temporal context in central-southeastern Brazil.