Otoliths contain so much information about the lives of fish.
|
Mystery of fish early life history
A suite of techniques, including the recent revolution in radio telemetry as resulted in a wealth of information becoming available regarding the biology and spatial ecology of the adult phases, and the early life history phases of large-bodied species, which are big enough to attach transmitters. Unfortunately, the majority of early life history phase fish are tiny, and too small to track with conventional methods. Instead, their earstones (otoliths) are the primary source of information regarding the age, growth and habitat use of early life history phase fishes.
This comprehensive review on the use of otoliths in early life history fish ecology was published in Biological Reviews. |
Increased interest
There has been a boom in otolith research since the 1980s
|
First published in 1899, otoliths are known to contain information regarding the age and growth of fishes. By counting the growth rings (analogous to growth rings in tree trunks) scientists have been able to study the demographics of fish populations. Since the 1960s and 1970s, a range of new techniques have become available, including the ability to study the age, growth and spatial ecology of larval and juvenile fishes. This information has been pivotal in developing our understanding of recruitment processes in many species, particularly those we commercially harvest. Approximately 100 papers are published annually that use otoliths to examine the early life history ecology of fishes. Despite all this research effort, it is challenging to apply the numerous techniques available to extract information from fish otolith in an integrative manner, to provide a complete picture of fish early life history ecology.
Techniques employed to study fish otoliths fall into 2 broad categories: Those that explore otolith microstructure, and those that examine otolith chemistry. Furthermore, otolith microstructure reveals information about fish biology (eg., age and growth processes) while otolith chemistry reveals information related to spatial ecology (eg. habitat use, dispersal, migration). In the past decade, the majority of studies have been conducted on marine species, and focus on employing otolith microstructure techniques, to examine fish age and growth. Conversely, fewer studies are conducted on freshwater fishes, and only 5% of studies combine otolith microstructure and chemical analyses to explore broader, integrated objectives linking both biology and spatial ecology. |
Techniques available
Graph analysis reveals that some techniques are not being used to their utmost potential
|
New techniques, such as transgenerational marking, and MicroCT scanning will open new avenues to study the early life history ecology of fishes. Both techniques have only recently been developed, and there are few described applications, but the list is growing every year! A really exciting opportunity exists to combine transgenerational marking with other otolith-based techniques to provide some new insights into the lives of baby fish. Furthermore, MicroCT technology could pave the way for rapid data acquisition, revolutionising how data is collected for primary research, and fisheries management.
Many of these otolith-based techniques are the mainstay of fisheries-related research. However, they also could be applied to explore broader questions in ecology, and evolutionary biology. So many opportunities hinge on the incredible information stored inside the fish's ear! |
Starrs, D., Ebner, B.C., and C.J. Fulton (2016) All in the ears: Unlocking the early life history biology and spatial ecology of fishes. Biological Reviews 91: 86-105 doi: 10.1111/brv.12162 LINK
