Deep Sea: The Last Frontier
Sharks and fishes that inhabit waters deeper than 150 m (500 feet) are among the least-studied species in the world’s oceans, and deep-sea fisheries often become established in these depths before any research can be conducted on the biology and ecology of the targeted animals. This is especially problematic for deep-sea species because they tend to be slower-growing and reproduce later than their coastal counterparts, and are therefore less able to recover from overfishing. Shark species are especially vulnerable, as they often have very low productivity: for example, some gulper sharks produce only a single pup per reproductive cycle.
We are currently conducting research on the deep-sea fishes, sharks, and the fisheries in the Meso-American Region (MAR) to learn more about which species inhabit this region, how they are distributed, and how their populations might respond to increasing fishing effort. Working with local fishers, we are conducting some of the first research on these species in the MAR. We hope to learn which species might be the most vulnerable to over exploitation and identify critical habitats that need protection. Along the way we are also filling in our knowledge on the deep-sea ecosystem, expanding known ranges for species, and even potentially finding new species!
Baselines & Standardized Long Term Monitoring
How do you know your efforts to protect populations of marine wildlife and their critical habitats are successful? If you don’t have a starting point it’s difficult to measure a moving target. A baseline survey – basically a count of what is observed at a set of representative places at particular points of time – is used to assess the species diversity and abundance of a region at a certain period of time. This baseline serves as a reference point from which we measure changes over time and across different regions, including inside and outside of protected areas, and/or before or after a specific event, such as the implementation of a protected area or new regulations.
MarAlliance conducts standardized baseline surveys on a regular basis throughout Belize, and collaborates with partners in countries such as Mexico, Guatemala, Honduras, Cuba, Cabo Verde, Panama and Micronesia to develop and help implement these surveys. By focusing on “Big Fish” that often serve as sentinels of ecosystem change, we can identify where overfishing may be upsetting the delicate balance of the tropical ecosystem. Our findings will help to inform managers and shape conservation strategies so that these species continue to thrive, as do the human populations that depend on them.
Traditional fisher Evaristo Muschamp shows a recently extracted otolith collected as part of a study on yellowedge grouper age and growth. Photo: Cameron Rhodes
Biology of Threatened Species
Determining a species’ specific growth rate, size and age at maturity, and the rate at which it reproduces tells us a lot about its vulnerability to fishing exploitation. A slow-growing shark species that only produces 4 offspring every other year may not be able to recover from heavy fishing mortality. This is especially important information for threatened species that have been overexploited. Because growth rates and reproductive output vary so widely among species, and often by region, it is extremely important to study the growth and reproductive biology of threatened marine wildlife on a species-specific and regional basis.
Through fisheries-independent and -dependent means, MarAlliance has been determining the growth rates and age at maturity for species such as the Caribbean reef shark, Goliath grouper and several species of rays that are currently listed as data deficient by the International Union for the Conservation of Nature (IUCN). Results of our work have been integrated into peer-reviewed papers, management plans and species assessments.
A satellite tagged Hawksbill turtle yields information on its movements around Lighthouse Reef Atoll, Belize. Photo: Pete Oxford
Spatial Ecology of Threatened Species
Spatial ecology is the study of an organism’s use of habitats and ecosystems throughout its lifetime. A variety of factors influence spatial ecology, including, but not limited to: food availability, habitat type, season, reproductive activity, and predator avoidance. Not surprisingly, as an animal grows and ages, it will often change its pattern of habitat use. We study the spatial ecology of big fishes to detect these patterns and to identify those habitats that may be critical to the success of their populations.
As human populations continue to grow, habitat destruction and overfishing are changing the spatial ecology of sharks and rays. Several studies have shown that species abundance and diversity decreases with increasing proximity to human population centers. One of the most vulnerable groups of fishes are the sawfishes, and we have seen drastic reductions in preferred habitat (clean estuaries, mangroves and sandflats) for all five species of sawfishes. Once common throughout the Caribbean, the largetooth and smalltooth sawfish species have not been observed in recent years (over 25 years for the largetooth) and are now considered ecologically if not functionally extinct throughout the MesoAmerican reef region (Mexico, Belize, Guatemala and Honduras). By identifying critical habitats for big fishes, we hope to keep this pattern from continuing.
MarAlliance has revealed patterns of behaviour and movements in a range of large marine wildlife including turtles, manta rays, whale sharks and reef-associated sharks. See our publications page for our papers on this topic.
Traditional fisher Trace handlines for finfish off the reefs of Pohnpei. Photo: Rachel Graham
Sustainable Fisheries and the Reduction of Fishing Effort
For coastal developing countries, fishing for a range of species is often important for the livelihood, culture, and health of the human population. However, in many regions, catches are diminishing and the sizes of captured fishes is decreasing. Collecting data from fisheries can allow researchers to identify and address problems to ensure the continued health of fish populations and the communities that rely upon them.
Fishing operations in many tropical countries are generally on a small scale, often conducted from small vessels in areas that are easily accessible from shore. However, the use of destructive gears, such as nets and longlines, can have a negative influence on fish populations and endanger the success of future fisheries. Sharks are especially vulnerable to being caught by nets and longlines and are often targeted by fishers.
A better understanding of the fisheries, fishing effort, and landings coupled with trade flows will help to identify whether these fisheries are sustainable and meet international convention requirements. At present, there are no sustainable shark and ray fisheries known in tropical countries.
MarAlliance is working with numerous partners to characterize the scope of elasmobranch fisheries and associated markets and trade flows. Resulting information is being fed back into management strategies at local, national and regional levels such as MPA management plans, species-specific management, National Plans of Action (NPOA), listing species on the Convention for Migratory Species (CMS), and Convention on the International Trade in Endangered Species of Fauna and Flora (CITES) non-detriment findings (NDFs).
A happy crew of recreational fishers show off their wahoo (Acanthocybium solandri) prior to data collected on weight, length, reproductive condition and otoliths by the MarAlliance team. Photo: Rachel Graham
Many fishes desired by sport or recreational fishers are large, highly migratory species. These animals are often apex predators and indicators of ocean health. Because they are highly migratory, sport fish may be targeted by fishers in more than one country, complicating management. Belize has a long history of recreational offshore fishing, but the status of preferred stocks is currently unknown. Working with fishers and in tournaments, MarAlliance is helping to characterize the offshore recreational fishery in Belize to better understand the status of our sports fish stocks, especially their age and growth, reproduction, habitat preferences, seasonal preferences, food web dynamics, and diets.
A team member interviews a local fisher about his catches and perceptions on the state of the fisheries resources. Photo: Gaby Ochoa
Many tropical countries are data-poor when it comes to fisheries or information on marine megafauna. To fill the data gaps and support precautionary management measures, we have conducted socio-economic assessments of a range of small-scale fisheries including on reef-associated fish, sharks, Goliath grouper and deep-water fishes. Depending on the targeted group and information needed, the surveys are shaped as pre/post, retrospective, online surveys or catch reconstructions. Results are triangulated with fisheries-independent field surveys and, where possible, market surveys to better quantify the diversity, distribution, size and demography of species landed as well as seasonality of catches and market prices. Since consumption of marine resources is not the only driver related to the value of marine wildlife, we also conduct surveys to assess the status of sawfish and dive tourism generated by whale sharks and reef sharks. Results have been used to better tailor management and conservation efforts, including legislation for reef fish spawning aggregations, MPA designation, protection of coastal and reef-associated sharks, species protection for whale sharks (Rhincodon typus) and nurse sharks (Ginglymostoma cirratum), and proposed size limits for the Goliath grouper (Epinephelus itajara) fishery.
The team conducting perception surveys of sharks with coastal communities in Honduras.
Public Perception Assessments
In the quest to better raise public awareness about marine wildlife and notably sharks, we have conducted outreach and education initiatives throughout Belize since 1999. From 2001 onwards, these initiatives were expanded to several other countries including Madagascar, Micronesia, Mexico, Guatemala, Cuba, and Honduras. However, we needed to know whether our efforts had been effective in changing entrenched mindsets of fear or disgust. We also needed guidance in honing our conservation messages to better effect changes in the use of unustainable fishing gears such as nets and longlines, consumer preferences and stewardship of marine megafauna.
As sharks in particular are feared by many worldwide including Belize, we were keen to understand what lay behind this fear and subsequently identify communication strategies in order to mitigate that fear. Specifically, a national survey was conducted in Belize to assess the public’s knowledge, perceptions, and management preferences for elasmobranchs. It followed a standard pre/post format with 25 questions. Pre surveys were conducted in 2011, prior to outreach activities, and post surveys were completed in the winter of 2013/14 following a 2.5 year outreach campaign. The objectives of this survey with Belize’s public were to 1) Identify levels of knowledge, perceptions and attitudes towards sharks; 2) Reveal national patterns of consumption of shark meat; 3) Highlight proposed management and conservation options; 4) Assess the effectiveness of the strategies used in the outreach campaign.
Pre-survey results helped us to develop and tailor an outreach strategy that has provided many opportunities to educate and inspire, and helped to expand our outreach for sharks and rays along the MesoAmerican Reef. Results indicated that the Belizean public has a good basic knowledge of sharks and rays. Unfortunately, close to half of respondents of the post survey feared sharks and rays, with more women fearing sharks than men. Despite this fear, more than 80% of respondents supported the protection of sharks and rays in both 2011 and 2014. Belizeans believed that shark and rays were important to tourism, and therefore generate revenue for the country. However, we still need to increase awareness about the harmful health effects of consuming shark meat, particularly among men. Communities where shark consumption was highest included Belize City and southern coastal Belize.
Integrating perception surveys into management provides a highly replicable and strategic means of targeting conservation messaging and assessing often costly and time-consuming outreach efforts.
Large sharks accumulate high levels of neurotoxic methyl-mercury in their tissues which are passed on to consumers. Photo: Pete Oxford.
Is Eating Shark and Other Large Fish Healthy for You?
As a top predator on the food chain, sharks and other large predatory fishes are known to accumulate toxins acquired from the fish and other prey they eat throughout the course of their lives. Several published papers indicating that shark meat contains high levels of methyl mercury, which is a potent neurotoxin that is often derived from industrial processes, notably cement manufacturing.
Results from a recent study conducted by MarAlliance team members indicated that over 80% of sampled sharks at Lighthouse Reef Atoll in Belize were above the US Environmental Protection Agency (EPA) advisory levels of 0.3 parts per million (ppm) and over 37% were above the Federal Drug Administration (FDA) and World Health Organisation (WHO) advisory levels of 1.0 ppm. Previous research on methyl mercury levels in Goliath grouper conducted in Belize by MarAlliance suggests that mercury levels are high in animals larger than 55 cm TL, with many exceeding the US governmental advisory criteria for human health (Evers et al. 2009).
Although alarming, these results are not wholly unsurprising. Sharks and groupers are apex predators that are known to biomagnify toxins, including heavy metals such as mercury, due to the many food chain linkages existing in the marine environment. In humans, absorption of large pulses of mercury and continued ingestion above the advisory levels impacts cognitive abilities, memory and depresses serotonin levels.
US EPA and FDA advisories suggest that pregnant women should avoid eating fish such as shark and king mackerel and not eat more than two meals of fish or shellfish of lower mercury content a week (no more than 12 ounces or two average meals (see: What You Need to Know About Mercury in Fish and Shellfish). Because of the potential for developmental problems, these advisories are considered too high for pregnant women and young children, with suggestions that 0.12 ppm would be the acceptable threshold for these groups.