Marine protected area help recover fish without harming fishers

by Kyra Hartog, RJD Intern

With fisheries collapsing around the world, Marine Protected Areas (MPAs) have emerged as a potential solution to allow fish stocks to recover to a level at which they may be harvested sustainably. There are several types of MPAs, ranging from areas with some fishing allowed to no-take reserves. Though MPAs are widely considered as fishery recovery tools, there has been little empirical evidence showing the benefit a fishery may receive from an MPA. In addition, fishermen generally believe that an MPA will come with an economic cost, possibly related to decreased catch rates and increased boat travel time. In their recent paper, Kerwath et. al (2010) demonstrate the effectiveness of the no-take Goukamma MPA off the coast of South Africa with no apparent cost to fishermen.

The focus species of this study was the roman (Chrysoblephus laticeps), a seabream endemic to the South coast of South Africa that inhabits rocky reefs. The species is targeted as part of a larger fishery directed toward rocky-reef dwelling predatory fish. Due to lifestyle characteristics such as long lifespan and broadcast spawning reproduction, the roman is vulnerable to overexploitation and has been heavily depleted along the South African coast. Fishermen have been required to report species and boat catch data since 1985, providing five years of roman catch data before the Goukamma MPA was implemented in 1990. The study then examined catch data for ten years following the MPA’s implementation. The specific metrics used in this study were catch per unit effort (CPUE), which was used as an indicator for roman abundance, and total roman catch.

The researchers found that in the years leading up to and during the first year of the Goukamma MPA implementation (1985-1991), total roman catch decreased. A year after the MPA was implemented, roman catch began to increase. While there was no visible trend in CPUE before the MPA, researchers saw an increase in CPUE in the vicinity of the MPA after its implementation. Other areas further away from the Goukamma MPA exhibited neither positive nor negative effects with respect to CPUE or total catch. The researchers also did not see any increased travel time for fishermen due to the availability of access points to the fishery outside of the MPA.

Figure 1 from Kerwath et al. 2013

Figure 1 from Kerwath et al. 2013

The analysis of fishery data suggests to the researchers that the Goukamma MPA was effective in terms of fishery management and conservation of the roman. Though the exact reasons as to why the MPA was effective have not been investigated, it is believed that spillover and larval export from the MPA are the main contributors to the increase in CPUE around the MPA. When roman inside the MPA are protected, the biomass of the species will increase inside the area until the species has recovered sufficiently. Spillover of adults will occur, as the fish are able to grow without pressure from fishing. After males and females have recovered to pre-exploitation numbers, further CPUE increases can be attributed to recruitment of larval roman. The currents in the area can allow pelagic larvae to stay in the area of the MPA, where they can then settle out, grow and become available to the fishery.

This study gives strong positive evidence for MPA use as a fishery management tool. It provides empirical evidence for fishery recovery without great cost to the local fishermen. This study can be cited as reason to implement MPAs in areas around the world where species similar to the roman are in decline due to exploitation.

 

REFERENCE

Kerwath, S. E., Winker, H., Götz, A., & Attwood, C. G. (2013). Marine protected area improves yield without disadvantaging fishers. Nature Communications, 4, 1–6. doi:10.1038/ncomms3347

 

Plastic ingestion in fish

By Dani Escontrela, RJD Intern

Plastic debris is becoming a very prevalent problem for our world’s oceans. In fact two of the ocean’s largest features, the North Pacific and North Atlantic Subtropical gyres, have large patches of anthropogenic debris floating in its waters. There has been a significant amount of research that has found plastic or other anthropogenic debris in the stomachs of sea birds, invertebrates, marine mammals and planktivorous fishes. This debris can be harmful to these species as it can lead to physical entanglement, decreased nutrition from intestinal blockage, suffocation and decreased mobility; plastic can also be a vector for other harmful contaminants. As much research as there is about anthropogenic debris ingestion by the species mentioned, there aren’t many studies about ingestion by large marine fishes. This study set out to study this phenomenon by sampling large, pelagic predatory fishes from the central North Pacific subtropical gyre surrounding the Hawaiian Island archipelago.

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Ghostnets: marine debris is “ghostfishing”

by Emily Rose Nelson, RJD Intern

Annually 640,000 tons of fishing gear is lost, abandoned, or discarded at sea. This deserted fishing gear is known as “ghostnets” and has the potential to “ghostfish” by itself for decades. Ghostnets are a growing issue due to their ability to trap and kill large quantities of commercially valuable fish and threatened species, leading to a loss in food and biodiversity. This waste is of even more concern than other types of marine debris because it is developed specifically to catch marine organisms, often leading to their death.

It is clear there is a lot of trash in the oceans, however little is known about where debris occurs and what organisms it is interacting with. In order to address the problems resulting from ghostnets it is necessary to answer these questions. A team of researchers in Australia set out to understand some of the impacts abandoned fishing gear could have on biodiversity. By combining physical and ecological approaches they were able to predict entanglement risk (expected interactions between nets and turtles) of marine turtles in the Gulf of Carpentaria (GOC) region of Australia.

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Predator identity and its indirect effects on fishing

By Laura Louon,
Marine conservation student

Few would be surprised by the fact that fishing causes a reduction in the population of the targeted fish. That is a direct effect of fishing. But nothing in the ocean happens in a vacuum; if you decrease the number of individuals of one species, you are bound to see an effect on at least one other species, if not the entirety of the ecological community. When developing holistic management and conservation plans, it is therefore imperative that managers also consider the indirect effects of decreasing the population of a species in an ecosystem as to make the correct decisions. But how do you measure, and hence predict, these indirect effects?

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Shark Tagging with St. Thomas Aquinas High School

by Michelle Martinek, RJD Intern

 

This most recent trip on Captain Curt’s trusty vessel is likely one that the RJ Dunlap team and guests will not soon forget. What started as a bleary eyed, early morning trip to the keys turned into quite the adventure courtesy of our unpredictable friend Mother Nature. In the span of only an hour, we saw beautiful blue skies give way to a lightning storm that relentlessly pelted our faces with warm rain and rocked the boat with large waves. To a native Floridian, this changeability is no surprise. Our steadfast team and all the students from St. Thomas Aquinas braved the elements and had an extremely successful day, catching and collecting data on 6 sharks! Even wet and chilled, we returned a very happy crew.

The day began with a carpool of the RJD team with two new interns, myself included, setting off at 5am from RSMAS. After our trip leader David introduced us to the wonders of a deep fried breakfast burrito called the “tornado” and the following discussion of the recent “Sharknado” film, we arrived a little more alert to Captain Curt’s house at 7am. Our relief was great upon seeing that most of the supplies were still onboard from the previous expedition that weekend. Curt made sure we didn’t have it too easy however by informing us we would be going to the shallow waters of the everglades, meaning we had to completely re-rig all of the drumlines since they were set for far deeper water. After preparations were complete, we welcomed a wonderful group of students from St. Thomas Aquinas High School, most of whom are part of their school’s marine science club, and set off.

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Shark Tagging with Island Christian School

by Jessica Wingar, RJD Intern

What an interesting day out on the water. When I woke up that morning, I could feel that it was going to be a great day. As I was walking to my car, I checked the weather forecast; it said that there was little wind. I became very excited because that meant that we could possibly go to the reef, a deeper site, because the water would not be too rough. I drove with Kyra to the Keys, and we couldn’t stop talking about all of the possibilities of this trip.

We arrived at Captain Curt’s house at 7:30am and began loading all of the equipment that we would need for the day onto the boat. We loaded yoyos, ten drumlines, a ventilation pump, and many other items. Once everything was loaded, we asked Curt where we were going today and found out that we were going to a new reef site called 62 Line. This switch to a deep site, meant that we had to undo the extension lines and roll them all up again; our lines were over 130ft long!

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