Survival after arrival: how post-settlement mortality shapes population connectivity and climate change resilience in a coastal marine fish

A project undertaken at the School of Biological Sciences, The University of Queensland and supervised by Cynthia Riginos

Co-investigator: Libby Liggins, The University of Queensland

Most coastal fishes start life as planktonic larvae swimming for days to months before 'settling' to the adult habitat. Thus, fish must survive this perilous larval journey and the high mortality transition to adulthood. This begs the question - is the composition of an adult population shaped more by who arrives (larval supply) or by who survives (post-settlement selection)? The persistence of coastal populations under changing climate conditions will depend on some combination of range shifting (a shift in larval supply) and adaptation (post-settlement selection). Thus, understanding the importance of larval supply versus post-settlement selection for population persistence, and having the ability to identify shifts in their relative contribution, is gaining urgency. Using tidepool fishes we are examining the relative survival of immigrants and local recruits, the degree to which post-settlement selection reduces connections between populations, and how settlement and selection differ by latitude across the species’ range. We are using otoliths (fish ear bones) to gain information about the origin and settlement fitness of individual fishes and genetics to infer larval origins and the nature of post-settlement selection.

Captions to Figures

Figure 1. Collecting sites for focal species: Bathygobius cocosensis, Lepidoblennius haptodactylus, and Enneapterygius atrogulare (=A. rufopileus). Adult fishes have been collected at least once from each location, providing latitudinal sampling. At present, we are waiting for genomic results from all seven populations of B. cocosensis and for four populations of L. haplodactylus (Hastings Point, Pt. Macquarie, Shellharbour, and Bateman’s Bay). These data will provide geographic context for adult patterns of genetic structuring and should identify loci that show a strong correlation with latitude (candidates for selection). 

Figure.2. Pilot results from mark-recapture study of Bathygobius cocosensis. Residency appears to be greater in high intertidal pools that are less frequently submerged by seawater. Number of individuals captured by total number marked the previous month are indicated (i.e., “8/22” indicates that of 22 marked individuals, 8 were recaptured the subsequent month).

Figures 3 & 4. Collecting fish from tide pools. University of Queensland honours student Lucie Malard collecting fishes at Point Cartwright, QLD. Tidepools are pumped out with the aid of bilge pump connected to a car battery.


Figure 1.

Figure 2.

Figures 3 & 4.