We evaluated whether we could more rapidly estimate the age of longnose skates using a new approach, namely, shining near infrared light through their vertebrae. This approach produced age estimates comparable to those from traditional methods for most of the included age range, and in a quarter of the time. Findings show promise for increasing the amount of age data available for age-structured population assessments to monitor the status of this species.

Although the optimal physiological condition is high salinity, the marine-originated goby (Gymnogobius petschiliensis) also uses freshwater habitats. Field surveys showed that, although most adults of the species usually inhabited freshwater habitats in central Japan, spawning occurred mainly in estuarine areas. This suggests that they needed to migrate downstream for successful reproduction, which was inhibited in freshwater because of physiological constraints.

Recently, cyanobacteria that have not been observed in the past have been occasionally found in South Korea. In this case, the question arises as to whether these species are newly introduced from outside or whether native species have became conspicuous due to environmental changes, such as global warming. In this study, we use morphology and genetics to provide a plausible answer to this question.

Freshwater crayfish are among the most endangered animal groups in the world. We examined bias associated with baited traps for members of this diverse group in Australia. We confirmed that traps predominantly captured large males, whereas their abundance was underestimated two- to three-fold when compared with that from baited video surveys. Animals avoided traps with a captive crayfish. Video techniques can better inform conservation efforts.

The highly resident Mustelus mustelus from the Langebaan Marine Protected Area (MPA) have been protected from fishing activities for 30 years. Residency of M. mustelus inside the MPA is largely as a result of their movement to avoid warm and cold water outside their thermal preference. The influence of environmental conditions on how an MPA is used by this species emphasises the importance of considering environmental preferences in spatial conservation initiatives.

We provide a detailed view of roosterfish (Nematistius pectoralis) diel vertical behaviour along a continuous rocky habitat derived from pop-up satellite archival tags. Contrary to shallow-water habitats, roosterfish were diurnally active and exhibited diel vertical behaviours. Alterations of vertical behaviour across habitats illustrate how habitat influences behaviour and the importance of studying organisms throughout their range.

This study explored electronically tagged fish as autonomous monitors of aquatic habitats. Using a migratory freshwater fish in Lake Erie, we showed that the fish could provide information on temperature patterns from times and places that researchers were not able to measure. This approach could become an integral part of ongoing research to understand habitat changes in aquatic environments.

We respond to criticisms published in Marine and Freshwater Research on a paper of ours published in another journal on the relative importance of direct and indirect effects of salinity on stream invertebrates. We also present new data to support our conclusions and discuss how the question we sought to address can be advanced.