Identification of freeze-thaw artifact in fresh and decomposed black rockfish (Sebastes melanops) and steelhead trout (Oncorhynchus mykiss).

Identification of freeze-thaw artifact in fish can help to determine whether they have been harvested within the appropriate season and monitor adherence to fishing regulations. Recognition of freeze-specific changes will also prevent potential misinterpretation due to decomposition, disease, injury, or species variation. An initial survey using black rockfish (Sebastes melanops) identified which tissues reliably exhibit freeze artifact. Tissues were exposed to different treatments: immediate formalin fixation; refrigeration or storage at room temperature for 24, 48, or 72 hours; or freezing for 1, 8, or 28 days. Three fish underwent a combination of treatments. Tissue changes in each treatment group were compared macroscopically and microscopically. Macroscopic changes in frozen-thawed and never-frozen fish overlapped somewhat; however, microscopic findings of skeletal myocyte cavitation, lens liquefaction, and brain tissue fractures were consistent findings only in frozen-thawed tissues. A validation study was then done to establish the accuracy of microscopic analysis. Brain and paired ocular and skeletal muscle samples from 61 steelhead trout (Oncorhynchus mykiss) were fixed in formalin either fresh or after being frozen for 4 weeks. Weighted kappa values showed both high observer accuracy and interobserver agreement in the identification of freeze-thaw status. Based on these findings, microscopic changes in the skeletal muscle, eye, and brain are considered consistent and easily identifiable indicators of a previous freeze-thaw cycle and should not be confused with a pathologic process.

ANTICOAGULANT EXPOSURE IN GOLDEN EAGLE (AQUILA CHRYSAETOS) POWER LINE ELECTROCUTION AND WIND TURBINE MORTALITIES.

Golden Eagles (Aquila chrysaetos) are susceptible to anthropogenic mortality factors, including toxic compounds in the environment such as anticoagulant rodenticides (AR) and sources of man-made energy. The physical and behavioral effects of some toxins may predispose eagles to certain causes of death (COD). To investigate the influence of ARs on mortality of Golden Eagles at wind turbine farms, we randomly tested liver samples from 31 eagles found dead on wind farms and submitted to the National Fish and Wildlife Forensic Laboratory from 2013-20. The comparison group was composed of 31 Golden Eagles sampled during the same time frame with a COD of power line electrocution as a proxy for a relatively lower effort and altitude activity. Associations between COD, AR exposure, sex, and life stage were assessed. In each group, 12 birds (35%) were found to have been exposed to brodifacoum or bromadiolone prior to death. Logistic regression showed no significant association between COD and sex (P=0.194) or life stage (P=0.895). Across both mortality types, life stage was not a significant predictor of AR exposure (P=0.725), but males were more likely to have been exposed to ARs (P=0.032). These findings suggest that there is no difference in the influence of anticoagulant exposure on higher and lower altitude activity in Golden Eagles.

CHRONICALLY EMBEDDED LEAD PROJECTILES IN WILDLIFE: A CASE SERIES INVESTIGATING THE POTENTIAL FOR LEAD TOXICOSIS.

Research has demonstrated that intramuscularly embedded lead in humans and rats may cause direct plumbism, albeit rarely, and has identified risk factors to this end. To the authors' knowledge, this has not been investigated in wildlife, despite a high incidence of embedded lead in these animals secondary to cynegetic activities. Fourteen wildlife cases submitted to the National Fish and Wildlife Forensics Laboratory for cause-of-death determination had chronically embedded lead projectiles that were unrelated to the cause of death. Tissue lead levels were measured in all cases and revealed clinically significant hepatic lead levels in two cases. The results corroborate comparative literature and suggest that embedded lead fragments carry a low risk for direct plumbism, even in the face of risk factors such as fractures, inflammation, and projectile fragmentation. Wildlife morbidity and mortality from embedded lead is more commonly realized secondary to incidental ingestion and ballistic trauma rather than by direct toxicity.

Using an alternate light source to detect electrically singed feathers and hair in a forensic setting.

Mortality due to electrical injury in wildlife may occur in the form of lightning strike or power line contact. Evidence of electrical contact may be grossly obvious, with extensive singeing, curling, and blackening of feathers, fur, or skin. Occasionally, changes may be subtle, owing to lower current or reduced conductivity, making a definitive diagnosis of electrocution more difficult. We describe the use of an alternate light source in the examination of cases of lightning strike and power line contact in wildlife, and the enhanced detection of changes due to electrical currents in the hair and feathers of affected animals. Subtle changes in the wing feathers of 12 snow geese and 1 wolf that were struck by separate lightning events were made obvious by the use of an alternate light source. Similarly, this technique can be used to strengthen the evidence for power line exposure in birds.

Intestinal rupture in a Mexican gray wolf (Canis lupus baileyi) in association with ingestion of a diazinon-impregnated cattle ear tag.

A free-ranging Mexican gray wolf (Canis lupus baileyi) suffered intestinal rupture following ingestion of an insecticidal cattle ear tag. Subsequent organophosphate toxicosis as a cause of the rupture was speculated. Insecticidal ear tags could represent a poisoning risk in canids and other wildlife scavengers.