Fish Kill Investigation-Mullet Necropsy
Channel: Sean Anderson
Date: 2018-08-02

Ormond Lagoon and the surrounding waterways/inflows began experiencing a dramatic fish kill starting on or about Friday, July 27.  By Monday, July 30 scientists from the US Fish and Wildlife Service and California Fish and Wildlife Service (formerly California Fish and Game)  were already coordinating with other state and Ventura County partners to get in and collect samples of water and fish.

We here in ESRM were asked if we might assist with the response by facilitating the necropsies of collected fish.  On Tuesday, August 1, we hosted Dr. Mark Okihiro from California Fish and Wildlife's Vista Office, our regional fin fish necropsy specialist.  Here Dr. Okihiro dissects a striped mullet (Mugil cephalus) collected a few hours before.  In our video he goes on to explain that the gross examination is looking for discoloration or lesions on the skin and internal organs.  Particular targets for this investigation were gills, gonads, and liver.  Samples were collected for both organic pesticide contamination characterization (the culprit in our most recent event in this same area, which occurred in 2015) and tissue cross sections (thin-sliced cross sections of paraffin-mounted and formalin-preserved organs) for exploration of tumor or other deformities.

While not directly related to the assay for toxic exposure, our ESRM and Pirate Lab crew also saved the intestinal tract for subsequent microplastic assays and the otoliths for aging.  This is for our ongoing work characterizing microplastic exposure, fate, and transport across the coastal zone and for our training of undergraduates in cutting-edge environmental impact assessment. 

This was a great lesson in how to examine fish possibly exposed to a toxin.