What Happens When A Poisonous Fish Gets Poisoned?

by Melanie Abecassis and Thierry Work

Between June and October 2010, beach-goers all around the Hawaiian Islands were discovering dead pufferfish on the beach or distressed in the ocean, puffed up and floating. In some cases, puffers were found in pairs with one fish biting and holding another. Occasional reports of puffers acting aggressively towards each other were received, and in one instance, a puffer was observed actively attacking snorkelers in the water. Thus started a five-year long episode of CSI-Fish-Hawai‘i.

Pufferfish are poisonous fish and are mostly solitary animals that rarely interact with other fish. Researchers collected sick puffers, held them temporarily in fish tanks and noticed they struggled to remain submerged, ending up “bobbing” at the surface. This phenomenon affected three species of pufferfish, mainly stripebelly puffers (Arothron hispidus) with a minority of spotted puffers (A. meleagris) and porcupine fish (Diodon hysteria). Populations of spotted puffers that are routinely monitored by scientists on the west coast of Hawai‘i Island declined precipitously starting in 2009, and remained low from 2010 onwards, whereas no evident population change was seen for porcupine fish or stripebelly puffers.

Because pufferfish are highly toxic, they are not typically targeted for human consumption (except in Japan, where the meat of some pufferfish is considered a delicacy. Called fugu, it is extremely expensive and only prepared by trained, licensed chefs who know that one bad cut means almost certain death for a customer). However, fish die-offs are important to investigate in tropical marine ecosystems because they are honest signals of environmental perturbations that could damage populations of native species or, in some cases, impact public health.

Using various laboratory tools, veterinarians and chemists with the U.S. Geological Survey’s National Wildlife Health Center, Honolulu Field Station and NOAA’s National Ocean Service spent five years trying to identify the cause of death and discovered a series of marine toxins comprised of very small molecules that had never been identified before as the likely cause of this mass mortality. The toxins led to liver failure, acid base imbalance in the blood, and subsequent inability of fish to remain submerged. Their findings are striking in that 1) a marine toxin killed a species of fish that is, itself, toxic, 2) they identified a plausible mechanism (liver failure) to explain clinical signs of affected fish, and 3) this epidemic likely depleted some pufferfish populations. Scientists suspect the marine toxin was ingested, but the source remains a mystery.

PIFSC scientists collaborated on this project to investigate whether there were any abnormal ocean conditions that could have explained the timing of the fish die-off, but no clear link between ocean conditions and fish mortality was identified.

This study provides a template for marine fish kill investigations associated with marine toxins and highlights the need for more rapid and cost-effective methods to identify new marine toxins, particularly small molecules.

Read more: Pufferfish mortality associated with novel polar marine toxins in Hawaii

Scientists assess herbivorous fishes and coral health off West Maui

In recent weeks, Coral Reef Ecosystem Division (CRED) staff participated in two separate projects for which they conducted surveys and other field work near Kahekili, Maui, in Hawai`i.

Kevin Lino conducts a belt-transect survey of fishes off West Maui in September. NOAA photo by Darla White, Hawai`i Department of Land and Natural Resources

Surveys help evaluate West Maui management area

Ivor Williams and Kevin Lino of CRED and staff from the Hawai`i Department of Land and Natural Resources’ Division of Aquatic Resources (DAR) on Sept. 24–29 conducted the latest in a series of fish, benthic, and urchin surveys at the Kahekili Herbivore Fisheries Management Area (KHFMA) off West Maui.

These surveys are part of a project, funded by NOAA’s Coral Reef Conservation Program (CRCP), through which CRED has been providing survey and analytical support to the DAR to assess the effectiveness of the KHFMA. Current plans are for this collaboration to continue through late 2014, when it will be five years after the establishment of this marine protected area.

Whitebar surgeonfish (Acanthurus leucopareius) and convict surgeonfish (A. triostegus), seen in the above photo, are examples of fishes protected in the Kahekili Herbivore Fisheries Management Area, where regulation prohibits these activities: to injure, kill, possess, or remove any rudderfish, parrotfish, surgeonfish, or sea urchin. NOAA photo by Kevin Lino

Coral reefs now in the KHFMA have been affected by blooms of invasive algae in recent years. In the 10 years prior to establishment of the KHFMA in 2009, three significant algal blooms were documented and coral cover there at the DAR’s long-term monitoring site declined from 55% to 33%. Concern about the rapid decline of the coral reefs along that part of West Maui and the desire to prevent a coral-to-algal “phase shift” (a persistent change of state from coral- to algal-domination), led to the establishment of the KHFMA.

A bluespine unicornfish (Naso unicornis) grazes on algae on a shallow reef off West Maui. NOAA photo by Kevin Lino

Within the KHFMA, herbivorous fishes are protected, but other groups of fishes can still be harvested. This management approach is unusual and differs from full-closure measures. This CRCP-funded series of surveys will provide data that can assist in examination of the KHFMA as a means toward restoration of herbivorous fish populations and prevention of coral-to-algal phase shifts.

Study examines effects of sewage on coral health off West Maui

Erin Looney on Sept. 16–28 participated in a two-week study for a CRCP-funded project focused on examination of the effects of land-based sources of pollution on coral health off West Maui. Led by Cheryl Woodley, PhD, and Lisa May of the Hollings Marine Laboratory in Charleston, S.C., this environmental forensic investigation into causes of coral decline and mortality on nearshore reefs off West Maui will provide baseline data.

At Kahekili, poor water quality, algal blooms, and coral decline are thought to result from sewage effluents seeping into groundwaters from shallow-well injections. The intention of this project is to clarify the role of wastewater injection wells through assessment of porewater toxicity of aquatic life and identification of toxic substances, their sources, and toxicity levels.

During the recent study, water samples were taken to assess the level and identity of fecal-associated bacteria in area waters as evidence of sewage input. This research will provide local resource managers with data to examine potential links between wastewater effluent and adverse biological effects.

Looney helped collect samples, perform microbial assays, and train local managers from the DAR, U.S. Environmental Protection Agency, National Park Service, and NGOs in the methods used for this type of experimentation. She plans to return to Maui this winter to conduct follow-up surveys and microbial analyses.

By Ivor Williams and Erin Looney