Understanding the Impacts of Trawl Fishing

Latest update June 5, 2019 Started on October 10, 2018

The Sea of Cortes is a spectacularly productive, vibrant, and diverse inland sea in Mexico, but destructive commercial fishing methods are putting this ecosystem at risk. Scientists in Baja California Sur are working to understand what impacts the commercial shrimp trawling industry is having on the nearshore deep-water ecosystems in the southern Sea of Cortes. What damages have already been inflicted? How is the seafloor community responding? Are there still areas where unaffected communities are thriving, and if so what do these look like?

El Mar de Cortés es un mar increíblemente productivo, lleno de vida, y diverso que se ubica en el lado Pacifico de México, pero métodos destructivos de la pesca comercial han puesto en riesgo estos ecosistemas marinos. Científicos en Baja California Sur están investigando los efectos de la pesca de arrastre del camarón en los ecosistemas costeros profundos en el sur del Mar de Cortes. ¿Cuales daños ya existen? ¿Cómo responda la comunidad marina? ¿Todavía existen comunidades inafectadas que están prosperando, y si existen, donde, y como son?

October 10, 2018
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We are currently planning our fieldwork for the summer sampling season. The most difficult part of using a mini ROV like the Trident is making sure that the data we collect are quantitative instead of qualitative. This means that instead of being able to compare only qualitatively which animals we see during our various transects, we can also compare how many of each animal we saw per square meter (animal density) on each of our transects. In order to be able to calculate densities, we need to know the area (in square meters) of each of our transects. Flying the ROV manually like you saw in our practice video does not let us calculate the surveyed area because neither the speed, nor the camera angle, nor the height of the ROV off the bottom remain constant, so we had an idea. We will build a small sled for the ROV that we can pull across the seafloor directly with our boat (see picture below). This way we can maintain a constant camera angle and altitude as well as a constant speed, since we are controlling the speed of the ROV directly from the boat. This strategy has the added bonus of stretching out our battery life, which means more data collected for each day out at sea. We are working on building our sled now using a few old, donated snow skiis (see picture below). We will keep you all posted on our progress!

Estamos planeado las salidas de campo por nuestro proyecto este verano. La cosa mas difícil de usar un mini ROV como el que tenemos es de asegurarnos que los datos sean cuantitativos en vez de solamente cualitativos. Eso significa que en ves de comparar solamente cualitativamente cuales animales vimos en nuestros transectos podemos comparar cuantos de cada animal vimos por metro cuadrado (una densidad de animales). Para que podemos calcular densidades necesitamos medir cuanta área (metros cuadrados) tiene nuestro transecto. Volando el ROV como vieron en el video en el post anterior no nos deja calcular eso porque ni la velocidad, ni el ángulo, ni la altura del ROV es constante. Entonces teníamos una idea. Vamos a construir un trineo por el ROV y arrastrarlo atrás de la panga en vez de volarlo (foto del diseño). Así podemos mantener un ángulo fijo, una altura constante, y una sola velocidad durante todos los transectos. ¡Además, va a durar mas tiempo la batería del ROV y eso significa mas datos por cada salida! Ahora estamos construyendo el trineo de unos esquís cortados (foto). Les mantendremos al tanto de nuestro progreso.

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same question here .... :)
Thank you for your questions! Anything that physically touches the seafloor will cause some level of disturbance. However, our design tries to minimize potential disturbances. Firstly, the sled is very small (just a little bit larger than the Trident itself) with approximately a 2 square foot footprint. Our design with 4 separate skinny skis also helps minimize the amount of material that is actually in contact with the seafloor. In addition, the goal is to keep it as lightweight as possible. The tricky thing here is that the sled must be heavy enough that it doesn't get pulled up off the bottom while we pull it behind the boat. This will require some experimenting. It will be key that we have live video for the design stage. This way we can evaluate our own disturbance and figure out the best way to minimize it quickly and efficiently.
Hi, nice project ! Take a look in my expedition blog, we add weight to the cable and dragged the TRIDENT with the boat at relative constant distance to the seafloor. If you keep the TRIDENt down the boat you can use the GPS track to measure how much distance you cover. Cheers

Hello everyone. We completed our first ocean dives this past week as part of our training. Please enjoy this short video and leave us some comments! It’s not that easy driving the ROV!

Saludos a todos. Ya cumplimos nuestras primeras salidas con el ROV la semana pasada. En esas salidas empezamos a practicar navegando con el ROV en el mar. Disfruten el video corto y déjenos sus comentarios. ¡No está tan fácil manejar el dron!

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This is great! You managed to fly close to the bottom and I'd say pretty steadily! Can't wait to see more!

The shrimp trawling season is in full swing. Along with heavy northerly winds and cooler water, the new year has brought even more trawling boats to the Bay of La Ventana, our study site. Although we are now armed and ready to investigate their impacts with our new S.E.E Trident miniROV rough weather has made getting into the water a challenge. Hopefully, we will get some calmer days soon and begin collecting data from the freshly made trawling scars. Just this weekend we observed 4 commercial trawling boats in the bay at one time!

Ya ha comenzado la temporada de la pesca de arrastre del camarón en el sur de la Baja en el Golfo de California. Junto con vientos fuertes del norte y las bajas temperaturas del agua, el nuevo año ha traído todavía más barcos de arrastre a la Bahía de La Ventana, nuestro sitio de investigación. Aunque estamos listos para investigar su impacto con nuestro nuevo S.E.E. Trident mini ROV (robot), el tiempo tormentoso ha impedido tomar muestras. Ojalá pronto vengan días más calmados y podamos empezar a trabajar. ¡Solo este fin de semana observamos 4 barcos de arrastre en la Bahía al mismo tiempo! 


The Trident and I are on our way to Baja California Sur!

¡Estamos en camino a Baja California Sur el Trident y yo!


Yay! So excited for you Astrid. Can't wait to read your updates

Hi everyone!
I have great news to share today. Our expedition was selected to receive an OpenROV Trident – a portable remotely operated vehicle- through the Science Exploration Education Initiative! This means that we will be back in the water in the new year gathering more data on the impacts of bottom trawling on the deep-water coastal ecosystems in the southern Sea of Cortes. Thank you so much to all of you who have followed this expedition and welcome to all our new followers. I can’t wait to post some of the beautiful videos we will be getting with our new ROV!

¡Hola a todos! Hoy tengo buenas noticias para ustedes. ¡Nuestra expedición fue seleccionada para recibir un OpenROV Trident, un robot submarino, a través del programa de la iniciativa por la ciencia, exploración y educación! Eso significa que volveremos al aguael año que viene para obtener más datos sobre los impactos de la pesca de arrastre en el ecosistema profundo de la costa sureña del Mar de Cortés. Gracias a todos aquellos que ya seguían esta expedición y bienvenidos todos los nuevos seguidores. ¡Estoy deseando poder compartir con ustedes alguno de los nuevos videos del ROV! ¡Hasta pronto!


We have started going through our initial ROV videos (preliminary data) that we collected last year during our pilot sampling project. Video from a local protected area Cabo Pulmo National Marine Park has found dense communities of garden eels at around 30m depths. These have been notably absent from our videos in the trawl-impacted sample region.
There are three species of garden eels in the Gulf of California all in the genus Heteroconger. These eels live groups (or gardens) with each eel in it's own burrow in sandy substrate. They feed on zooplankton in the waters just above their burrows by sticking their heads and part of their bodies up out of their holes. When approached they quickly retreat back into their burrows for safety. Because these animals live on flat, sandy bottoms, they are vulnerable to trawl nets, which dig into the top layer of the seafloor. Learn more about garden eels by watching the attached video from a science article in the New York Times. We will need more video and higher quality video to try to get robust density estimates.

Hemos empezado a analizar los primeros videos del ROV (un robot submarino operado por control remoto con cámaras que nos prestaron de CIBNOR), que fueron obtenidos el año pasado como parte de un proyecto piloto. Uno de los videos del Parque Nacional Cabo Pulmo muestra comunidades abundantes de anguilas de jardín a una profundidad de unos 30 metros. Hasta el momento no hemos encontrado esas especies en videos tomados sobre áreas impactadas por redes de arrastre. Existen tres especies de anguila de jardín en el Mar de Cortes, todas pertenecientes al género Heteroconger. Estas anguilas viven en colonias, de modo que cada individuo se entierra en una madriguera en la arena. Se alimentan de plancton que capturan sacando sus cabezas y parte del cuerpo, pero en el momento en que llega algún peligro se esconden rápidamente en su escondrijo, enterrándose por completo. Debido a que estos animales viven en fondos planos y arenosos son vulnerables a las redes de arrastre, que remueven el sedimento de estos hábitats. Aprende más sobre las anguilas de jardín con este video del New York Times. Serían necesarios más videos y de más alta calidad para estimar el efecto negativo de estas las redes para las anguilas de jardín en el Mar de Cortes, en la zona costera de Baja California Sur.

Expedition Background

The Gulf of California a highly productive, incredibly diverse region that provides important economic resources including both fishing and ecotourism industries. Dubbed 'the world's aquarium" by Cousteau, it is home to a variety of endemic species, supports some of the northernmost coral reefs in the world, and hosts charismatic top predators like whales, hammerhead sharks, and pelagic manta rays. Naturalists and scientists have been exploring the Gulf of California for a long time, but until recently all of this exploration has been limited to only the shallowest, most accessible depths even as human impacts have extended much deeper. With new technologies like ROVs, we can now explore deeper depths, better understand our impacts and how to mitigate them, and make hands-on ocean experiences possible for even those who can't swim!

Our expedition aims to explore the ecosystems at the limits of SCUBA-accessible depths of the southern Sea of Cortez in the Gulf of California using the SEE Trident ROV with two main goals. Firstly, we will quantify and monitor the impacts of shrimp trawling on the coastal marine ecosystem of the southern Gulf of California. The shrimp fishery is the largest fishery in Mexico and consists of a small boat fleet and a commercial trawler fleet. Historically shrimp trawling has been mostly restricted to the continental side of the Gulf; however, in recent years commercial shrimp trawlers have become a common site on the southern peninsula side as well. Quantitative assessments of their impacts, especially below scuba depths, are urgently needed in the region. The current lack of data hampers the passing of regulations on this destructive mode of fishing. Trawling has been shown to be highly disruptive and destructive in various habitats; however, without local data, regulators refuse to act. Trawling creates a large amount of bycatch (with ratios of bycatch to target catch as high as 10:1!), and because it involves dragging heavy gear along the ocean floor, seafloor-living animals such as corals or garden eels can be harmed. Corals and other structure-forming animals create habitat for many other species, so trawling can potentially have long-term, ecosystem-wide consequences. This can negatively impact the local, small-scale fishers that depend on a healthy ecosystem to feed their families. To date we have collected some preliminary data from the bay of La Ventana and from Cabo Pulmo Marine Reserve using an ROV borrowed from our collaborators at UABCS and CIBNOR (see photos below, from Dec 2017). We still need to collect more data in order to be able to reach any solid conclusions, however. Because the western side of the Gulf of California was considered ‘nearly pristine” only a decade ago and remains one of the few places on Earth where large predators are still relatively common, scientists bear the responsibility of collecting the data required to successfully manage the system and protect the impressive biodiversity of this sea.

The second main goal of this expedition is community education, outreach, and partnerships. We are working together with local schools through personal relationships with local educators and the community that we have built up over the last half decade. We have been developing basic marine science curricula and laboratory exercises to increase hands-on science experience for local students. Because few of them have ever ventured further than knee-deep into their ocean, we plan to share our ROV video and survey results in their classrooms. This will allow students to get more familiar with their oceanic backyard and will hopefully inspire a sense of wonder and responsibility for their beautiful, unique marine ecosystem. By giving students the opportunity to interact with technology and scientists, we hope to spark long-lasting interest in STEM fields, especially in engineering, marine science, and environmental stewardship.

Métodos destructivos de la pesca comercial han puesto en riesgo los ecosistemas marinos. En colaboración con científicos de UABCS y CIBNOR, estamos investigando los efectos de la pesca de arrastre del camarón en los ecosistemas costeros de Baja California Sur. Documentaremos los efectos con una comparación de biodiversidad y abundancia entre áreas arrastrados y no arrastrados en la costa sur de Baja California. Realizamos este trabajo con la esperanza que esta información sea útil por científicos, comunidades locales, políticos, y conservacionistas. Una meta principal de este proyecto es de compartir nuestras resultados y videos con estudiantes y educadores para ayudar a llevar el tema de la conservación de ecosistemas marinas hasta las salas y hasta la conciencia de la futura generación de ciudadanos.

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