Monday, November 21, 2016

Protecting the reef fish we catch: the case of parrotfish

We already know that parrotfish (Labridae: Scarini) are large (and beautiful!) fishes that play critical functional roles in reef environments when they feed, which in their case, we call “grazing”. Parrotfishes spend their day biting off bits and chunks of algae and other benthic organisms with their beak-like teeth. However, macroalgae may not be their preferred dish, they seem to like smaller diet items then what has been previously assumed. Because of this new finding, they have been recently reclassified as microphagous (“eaters of tiny particles”) (Clements et al., 2016), which by no means diminishes their importance in shaping the reef community. In other words, their nutrition comes from protein-rich autotrophic microorganisms, which in their turn are associated with macro organisms. By eating microorganisms, parrotfish affects the structure and composition of benthic communities by maintaining algae free corals. 
Unfortunately, fishing pressure on parrotfishes has grown in the last decades around the world, and in Brazil, it is not different. Small-scale fisheries are exploiting large numbers of parrotfishes from Brazilian reefs, which could be leading to significant changes in the community structure. In particular, three species, Scarus trispinosus (Valenciennes, 1840), Sparisoma frondosum (Agassiz, 1831) and Sparisoma axillare (Steindachner, 1878), labeled as threatened in 2014, have been intensively targeted, mostly on the northeastern coast.

Scarus trispinosus landings. Photo by Natalia Roos.
In the Brazilian northeast, fishermen use different gears, including gillnets, handlines and spearguns, depending on the parrotfish species targeted. The effects that gears have in a given fishing are important to be understood because they may change catch composition, catch per unit effort (CPUE) and fish size frequencies. Therefore, the understanding of the effects of gear may guide suitable management strategies to maintain fish populations and long-term fishing yields.
The paper “Multiple management strategies to control selectivity on parrotfishes harvesting” assesses gear size selectivity and fishing pressure on the three most caught species of parrotfishes in the Brazilian northeast. The results showed that the annual total catch of S. trispinosus was estimated in 9.4 tons, while S. frondosum and S. axillare (usually caught together) were estimated at 15.4 tons, totaling 24.8 tons of parrotfish fished per year in a tiny area of the Brazilian coast.
Both S. frondosum and S. axillare are being caught by gillnets and handline above the size of first maturity, however, the CPUE value for gillnets are much higher than handline. For S. trispinosus, which is caught with gillnets and spearguns, the scenario is worse. About 80% of all S. trispinosus caught were below the size of first maturity, and most of the immature individuals are coming from gillnet fishery. 

Besides parrotfish artisanal fishing being multi-gear, multi-species and multi-strategy, there are many other problems involving this kind of fishery. First, parrotfishes are also targeted by unreported recreational fishing. Second, Sparisoma species are targeted by trap industrial fishing and exported to other countries. Third, some spearfishermen also hunt at night, when parrotfishes are asleep and much more vulnerable. Fourth, parrotfishes are protogynous hermaphrodite (i.e., they begin their life cycle as a female than they shift to male), and not protecting the larger individuals (males) can lead to several consequences to their reproduction. 
Due to all of these reasons, a multiple strategy approach is suggested for parrotfish management. Besides controlling artisanal gears by establishing a slot size limit for handline and speargun (gears that fishermen can choose the size of fish) and increasing the gillnet mesh size, banning recreational fishing, night fishing and exportation of parrotfishes should be taken into account. It is also important to consider spatial planning to protect sensitive areas. Clearly, all of these measures have to be monitored to ensure good results.    
The implementation of these multiple management strategies may oppose the latest Brazilian Red List, which recommended banning S. trispinosus fishery, as this was classified as Endangered, although it could support the need to manage S. axillare and S. frondosum. These two species are classified as Vulnerable and could be fished under restrictions. A repeal of the list would be a serious hindrance for the conservation and management of parrotfish. On the other hand, if this list is implemented, all the vulnerable species will require specific management measures, and this study is a timely contribution for the ecologically relevant and iconic groups of parrotfishes.

by Natalia Roos


Clements, K. D., German, D. P., Piché, J., Tribollet, A., & Choat, J. H. (2016). Integrating ecological roles and trophic diversification on coral reefs: multiple lines of evidence identify parrotfishes as microphages. Biological Journal of the Linnean Society.
Roos, NC, Pennino, MG, Lopes, PF, & Carvalho, AR. 2016. Multiple management strategies to control selectivity on parrotfishes harvesting. Ocean & Coastal Management, 134, 20-29.

Wednesday, November 2, 2016

What do fishermen know about dolphins and why do they know what they know?

Every time you go to a different beach, the most prudent thing to do is asking local people where the safe places to swim are (places with no currents, for example). It is very likely that you would ask people somehow involved with the sea at that particular beach, such as lifeguards, surfers, and fishermen. The reason is obvious: since they are used to the local environment, they would know the risks. The same is true when researching any specific characteristic of a given area. Sometimes, when you want to understand specificities of a place, the best option is to ask local people about its characteristics and dynamics. When living in a place and depending directly on its resources, people learn how to deal with things available at the place. As these people spend time on their daily activities, they also have more opportunities to observe and accumulate knowledge of the surrounding area. Gathering this local ecological knowledge (LEK) is a good way to learn about local features without spending too much time and money, since they would already be the result of local experience through years (and, sometimes, over generations).

Based on this, several researchers have been including the LEK into their studies to learn about the ecology and biology of different species. In our paper [“The behavior of the estuarine dolphin (Sotalia guianensis, van Bénéden, 1864) according to fishermen from different fishing environments”], we investigated the knowledge fishermen had about the behavior of a local dolphin. Even though dolphins are charismatic species, even for researchers, we still have a lot to learn about them because it is not that easy or cheap to study the behavior of species that spend most of their time underwater. Fishermen, on the other hand, have a natural chance to learn about dolphins, simply by performing their profession. But fishermen are just regular human beings and, as such, will have their cultural biases as well that will shape the knowledge they carry.

Sotalia guianensis, PHOTO:
Assuming that such biases would affect knowledge construction, we investigated how the perception of small-scale fishermen regarding the behavior of the estuarine dolphin (Sotalia guianensis) is affected by their education, experience, the type of environment where they predominantly fish, and the extent to which they are involved in dolphin watching tourism. We interviewed fishermen in routine contact with populations of S. guianensis in NE Brazil. Overall, most fishermen correctly reported the habitat, distribution, seasonality, and feeding behavior of this dolphin, besides bringing new insights into the dolphin’s reproductive behavior and its possible migration patterns. As expected, more experienced fishermen provided more details. Interestingly though, those fishermen that studied more years could also provide better details, perhaps suggesting that formal education could fine-tune their perception. Another important finding of this study is that fishermen’s knowledge is widely affected by the fishing environment they commonly use, because dolphins perform different behaviors depending on where they are. This finding has as additional implication and could be used as an attention flag to studies using LEK: you better carefully select your informants depending on what you want to learn, besides considering the effects of their cultural biases. Once you are aware of those limitation, inherent to human beings, be sure that fishermen, besides knowing a lot about fish, may also provide information on cetaceans that could be used in management and conservation when scientific sources are missing or insufficient. 

Manzan, M & LOPES, PFM. 2014. Fishers' knowledge as a source of information about the estuarine dolphin (Sotalia guianensis, van Bénéden, 1864). Environmental Monitoring and Assessment, 187: 4096.