Transgenerational Marking of Chinook Salmon Otoliths

Brandon Tyler Boehnke

doi:10.7273/000005164

Various tagging methods are currently applied in fisheries science for monitoring and managing fish populations worldwide. Tagging technology can often be limited by characteristics of the target species and can come with side effects such as lowering individual fitness. Otolith marking is a widely used alternative tagging technique that is effective in marking individual fish while not causing harmful side effects to the fish. An otolith mark will persist throughout the individual’s life, allowing for a permanent mark. A transgenerational isotopic otolith mark is the process of marking all offspring of a single individual by administering the mark to only the parent, with the mark transferring to one single generation, thus minimizing the handling of fish and other side effects of alternative tagging methods. This study explored a unique, transgenerational otolith mark in Chinook Salmon (Oncorhynchus tshawytscha). We explore marking a returned adult to discover if that mark can carry on one generation to its direct offspring. Adult Chinook Salmon were collected from Priest Rapids Hatchery in Mattawa, Washington, along the Columbia River. Pre-spawned adult female fish were injected with a stable isotope of Barium-137 for the mark both with a “High” (0.5mg/kg) and “Low” (0.05 mg/kg) dose. The adults were left until ready to spawn, after which eggs were collected, fertilized, and transported to a laboratory environment for incubation. Offspring were raised after hatch, and otoliths were then analyzed using Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) to verify the effectiveness of Barium-137 isotopic composition in the otoliths of the juvenile Chinook Salmon. Using a linear mixed effects model, a significant positive correlation was found between the post-mark holding time of the treatment fish and the level of enrichment in the offspring otolith. When isolating holding time as a variable, a categorical analysis of the treatment methods determined the “High” dose group to show a significant mark that was statistically larger than the control group. A trans-generational mark for management and research can be an inexpensive and effective method to reduce the direct handling of large numbers of fish while having the capability to mark significant percentages of populations, thus minimizing human intervention when monitoring managed populations of fish.

Transgenerational Marking of Chinook Salmon Otoliths

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