Marine mammal necropsy : an introductory guide for stranding responders and field biologists

The challenge of identifying cause of death in discarded bycaught marine mammals stems from a combination of the non-specific nature of the lesions of drowning, the complex physiologic adaptations unique to breath-holding marine mammals, lack of case histories, and the diverse nature of fishing gear. While no pathognomonic lesions are recognized, signs of acute external entanglement, bulging or reddened eyes, recently ingested gastric contents, pulmonary changes, and decompression-associated gas bubbles have been identified in the condition of peracute underwater entrapment (PUE) syndrome in previous studies of marine mammals. We reviewed the gross necropsy and histopathology reports of 36 cetaceans and pinnipeds including 20 directly observed bycaught and 16 live stranded animals that were euthanized between 2005 and 2011 for lesions consistent with PUE. We identified 5 criteria which present at significantly higher rates in bycaught marine mammals: external signs of acute entanglement, red or bulging eyes, recently ingested gastric contents, multi-organ congestion, and disseminated gas bubbles detected grossly during the necropsy and histologically. In contrast, froth in the trachea or primary bronchi, and lung changes (i.e. wet, heavy, froth, edema, congestion, and hemorrhage) were poor indicators of PUE. This is the first study that provides insight into the different published parameters for PUE in bycatch. For regions frequently confronted by stranded marine mammals with non-specific lesions, this could potentially aid in the investigation and quantification of marine fisheries interactions.

Section: Methodsmentioning

confidence: 99%

Discrimination between bycatch and other causes of cetacean and pinniped stranding

Quirós¹,

Hartwick²,

Rotstein³

et al. 2018

“…Investigation of carcasses in advancing stages of decomposition took place on a case-by-case basis or as required by a federally declared Unusual Mortality Events (UME). Necropsy techniques and sample collection (Pugliares et al 2007) were performed or supervised by IFAW personnel to maintain consistency in data collection.…”

Section: Methodsmentioning

confidence: 99%

Mortality trends of stranded marine mammals on Cape Cod and southeastern Massachusetts, USA, 2000 to 2006

Bogomolni¹,

Pugliares²,

Sharp³

et al. 2010

To understand the cause of death of 405 marine mammals stranded on Cape Cod and southeastern Massachusetts between 2000 and 2006, a system for coding final diagnosis was developed and categorized as (1) disease, (2) human interaction, (3) mass-stranded with no significant findings, (4) single-stranded with no significant findings, (5) rock and/or sand ingestion, (6) predatory attack, (7) failure to thrive or dependent calf or pup, or (8) other. The cause of death for 91 animals could not be determined. For the 314 animals that could be assigned a cause of death, gross and histological pathology results and ancillary testing indicated that disease was the leading cause of mortality in the region, affecting 116/314 (37%) of cases. Human interaction, including harassment, entanglement, and vessel collision, fatally affected 31/314 (10%) of all animals. Human interaction accounted for 13/29 (45%) of all determined gray seal Halichoerus grypus mortalities. Mass strandings were most likely to occur in northeastern Cape Cod Bay; 97/106 (92%) of mass stranded animals necropsied presented with no significant pathological findings. Mass strandings were the leading cause of death in 3 of the 4 small cetacean species: 46/67 (69%) of Atlantic white-sided dolphin Lagenorhynchus acutus, 15/21 (71%) of long-finned pilot whale Globicephala melas, and 33/54 (61%) of short-beaked common dolphin Delphinus delphis. These baseline data are critical for understanding marine mammal population health and mortality trends, which in turn have significant conservation and management implications. They not only afford a better retrospective analysis of strandings, but ultimately have application for improving current and future response to live animal stranding.

“…Gross necropsies should be performed by experienced prosectors on all carcasses following prescribed pinniped and cetacean protocols , Pugliares et al 2007). Ensure appropriate life history and individual identification characters are collected.…”

Section: Necropsymentioning

confidence: 99%

“…Reporting of gross necropsy findings should follow a standardized protocol , Pugliares et al 2007). A gross report should include as detailed a life history (from catalog ID if applicable) and case history as possible, and sketches, measurements, descriptions and samples taken and their disposition.…”

Section: Reportmentioning

confidence: 99%

Criteria and case definitions for serious injury and death of pinnipeds and cetaceans caused by anthropogenic trauma

Moore¹,

Hoop²,

Barco³

et al. 2013

137

140

Post-mortem examination of dead and live stranded beach-cast pinnipeds and cetaceans for determination of a cause of death provides valuable information for the management, mitigation and prosecution of unintentional and sometimes malicious human impacts, such as vessel collision, fishing gear entanglement and gunshot. Delayed discovery, inaccessibility, logistics, human safety concerns, and weather make these events challenging. Over the past 3 decades, in response to public concern and federal and state or provincial regulations mandating such investigations to inform mitigation efforts, there has been an increasing effort to objectively and systematically investigate these strandings from a diagnostic and forensic perspective. This Theme Section provides basic investigative methods, and case definitions for each of the more commonly recognized case presentations of human interactions in pinnipeds and cetaceans. Wild animals are often adversely affected by factors such as parasitism, anthropogenic contaminants, biotoxins, subclinical microbial infections and competing habitat uses, such as prey depletion and elevated background and episodic noise. Understanding the potential contribution of these subclinical factors in predisposing or contributing to a particular case of trauma of human origin is hampered, especially where putrefaction is significant and resources as well as expertise are limited. These case criteria descriptions attempt to acknowledge those confounding factors to enable an appreciation of the significance of the observed human-derived trauma in that broader context where possible.