Understanding the Impacts of Trawl Fishing

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

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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Preparation

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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