DOI: 10.5061/dryad.70rxwdc4p
title: Monsoonal wet season influences the migration tendency of a catadromous fish (barramundi Lates calcarifer)

description: Many animals exhibit partial migration, which occurs when populations
 contain coexisting contingents of migratory and resident individuals. This
 individual-level variation in migration behaviour may drive differences in
 growth, age at maturity, and survival. Therefore, partial migration is
 widely considered to play a key role in shaping population demography.
 Otolith chemistry and microstructural analysis were used to identify the
 environmental and individual-specific factors that influence migratory
 behaviour in the facultatively catadromous barramundi (Lates calcarifer)
 at two distinct life history stages: firstly, as juveniles migrating
 upstream into fresh water; and secondly, as adults or sub-adults returning
 to the estuarine/marine spawning habitat. Monsoonal climate played an
 important role in determining the migration propensity of juveniles:
 individuals born in the driest year examined (weak monsoon) were more than
 twice as likely to undergo migration to freshwater than those born in the
 wettest (strong monsoon) year. In contrast, the ontogenetic timing of
 return migrations to the estuary by adults and sub-adults was highly
 variable and not strongly associated with the environmental parameters
 examined. We propose that scarce resources within saline natal habitats
 during lower rainfall years may provide an ecological incentive for
 juveniles to migrate upstream, whereas more abundant resources in higher
 rainfall years may promote resident life histories within estuaries. We
 conclude that inter-annual climatic variation, here evidenced by monsoonal
 strength, likely plays an important role in driving the persistence of
 diversified life-histories within wild barramundi populations. 
description: # Monsoonal wet season influences the migration tendency of a catadromous
 fish (barramundi Lates calcarifer)
 [https://doi.org/10.5061/dryad.70rxwdc4p](https://doi.org/10.5061/dryad.70rxwdc4p) ## Description of the data and file structure Each data file contains otolith increment data. Each row contains information relating to a single year of individual-specific growth. * FishID: Unique identifier specifying each individual fish * Sex: Sex (where known, noting that barramundi are protandrous (i.e. male-female) sex-changers) * River: River/ Catchment where individual was captured * Sampling.Salinity: Binary variable describing habitat in which fish was captured (saltwater, freshwater) * Increment: Otolith increment width (um) * Age: Age (years) at which increment was formed * AgeStop: Age + 1 (required for cox proportional hazards models) * BRedge: Categorical marginal increment classification (N = Narrow; I = Intermediate; W = Wide) * capyear: Calendar year of capture * capdate: Date/ Month of capture * inccount: Number of annual increments within otolith * adjage: Adjusted fish age (years), accounting for number of increments, marginal increment classification and month of capture * newyearclass: Calendar year in which fish was born (assuming November 1 birthdate) * newfishyear: Calendar year that growth increment commenced * AMI: Australian Monsoon Index (area-averaged rainfall anomalies north of 25 degrees; see methods) * Lagged\_AMI: Australian Monsoon Index lagged by 1 year * WetDurStand: Standardised wet season duration (see methods for description) * Lagged\_WetDurStand: Standardised wet season duration, lagged by 1 year * WetTotalStand: Standardised wet season total flows * Lagged\_WetTotalStand: Standardised wet season total flows, lagged by 1 year * Length: Fish length at time of capture (mm) * PropFresh: Percentage of growth year spent within freshwater * Salinity: Categorical variable describing salinity experienced during year of growth ("freshwater", "estuarine" or "mixed") * Year1FreshMigration: Binary variable describing whether individual migrated to freshwater during first year of life (0 = no migration; 1 = migrated) * SaltwaterMigrant: Binary variable describing whether individual migrated from freshwater to saltwater during the life history (0 = no migration; 1 = migrated) * SaltMigration: Binary variable describing whether an individual migrated from freshwater to saltwater in a given year (0 = no migration; 1 = migrated) * AoM: Age (years) at which individual migrated from freshwater to saltwater * Psphlen: back-calculated fish length at end of growth year (mm) * Psphgrowth: back-calculated growth achieved during growth year (mm) * growth\_residual1: see methods for description * growth\_residual2: see methods for description * growth\_residual3: see methods for description **Upstream migration analysis** Data were filtered to remove individuals captured in freshwater and Ages &gt; 1. **Downstream migration analysis** Data were filtered to remove individuals captured in freshwater and SaltMigration=NA.