Rapid assessment of adult abundance and demographic connectivity from juvenile kin pairs in a critically endangered species.

The viability of spatially structured populations depends on the abundance and connectivity between subpopulations of breeding adults. Yet, for many species, both are extremely difficult to assess. The speartooth shark is a critically endangered elasmobranch inhabiting tropical rivers with only three adults ever recorded in Australia.

Robust estimates of a high / ratio in a top marine predator, southern bluefin tuna.

Genetic studies of several marine species with high fecundity have produced "tiny" estimates (≤10) of the ratio of effective population size () to adult census size (), suggesting that even very large populations might be at genetic risk. A recent study using close-kin mark-recapture methods estimated adult abundance at ≈ 2 × 10 for southern bluefin tuna (SBT), a highly fecund top predator that supports a lucrative (~$1 billion/year) fishery. We used the same genetic and life history data (almost 13,000 fish collected over 5 years) to generate genetic and demographic estimates of per generation and (effective number of breeders) per year and the / ratio.

Inferring contemporary and historical genetic connectivity from juveniles.

Measuring population connectivity is a critical task in conservation biology. While genetic markers can provide reliable long-term historical estimates of population connectivity, scientists are still limited in their ability to determine contemporary patterns of gene flow, the most practical time frame for management. Here, we tackled this issue by developing a new approach that only requires juvenile sampling at a single time period.