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Delaware National Estuarine Research Reserve

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We Monitor “What” in the Water?

Written on: August 15th, 2018 in Blackbird Creek ReserveEducation & OutreachResearch

An experience that is avoided by most college students became the beginning of a morning adventure… I was up before the sun; a rarity in itself. I had risen from the depths of my room to explore the waters of Blackbird Creek on a nekton trawl. The word nekton was absent from my vocabulary prior to this summer. Yet, within the first week of my internship I was gladly informed that nekton are any aquatic organisms that actively swim. Immediately intrigued by this foreign concept, I wanted to further my understanding and asked to join one of these so called “nekton trawls.”

I was later informed of an opportunity to assist Michael Mensinger and Drew Faulhaber on one of their monthly surveys. On August 6th, that fateful morning came and I was inquisitive as ever. Various questions flowed through my mind and I pondered: How does a trawl even work? What kind of data are we collecting? Why is this data important?” Although, all of my contemplations were soon contented when we set off and I was able to experience all of these things first hand.

Mike Mensinger and Drew Faulhaber measuring a striped bass.

The Blackbird Creek has been segmented into seven distinct zones based on salinity, then a randomized GPS point is selected within each zone.  The GPS point marks the place to begin the trawl. It is important to note that trawling is a method of fishing where a net is driven open by wooden boards, known as otter boards and runs along the bottom to collect various bottom-dwelling organisms. Setting up the trawl and driving the 22 foot motorized boat fell onto the two men I accompanied, while my job was to record start & end times and GPS coordinates. After reaching 300 meters in distance the trawl was lifted from the water and the captured organisms were placed into a fish processing bin. Once they were measured, and the data was recorded they would be returned to the water. Finally, before progressing into the next zone water quality and creek depth measurements were recorded.

Although this seems like a straightforward procedure, there is always room for mistakes to happen. During trawling in one of the zones, the net became caught and ripped from unknown debris residing at the bottom of the water way. The largest lesson to be learned from the entire situation is that scientists and people alike need to have the adaptability to overcome obstacles. Mr. Mensinger took this set back with a level head and having planned ahead was able to fix the net and continue the survey.

As we continued and eventually came to a close, it became evident that the high abundance of animals of this month were: white perch (Morone americana), hogchokers (Trinectes maculatus), channel catfish (Ictalurus punctatus), and blue crab (Callinectes sapidus). The data collected this month appears to be relatively consistent with Michael Mensinger’s  data collected last year, with the most abundant species being white perch, hogchokers, weakfish (Cynoscion regalis), and blue crabs (Mensinger, 2018).

A hogchoker caught during the trawling survey at Blackbird Creek on August 6th.

By comparing the data between the months and years a clearer picture of the area’s short-term and long-term biodiversity and biodiversity changes will become clearer, which helps scientists understand the effects of climate change and other forces on the nekton community. I am appreciative of Delaware’s National Estuarine Research Reserve for presenting me with a new perspective and the skills to match so that I may one day be able to improve society’s understanding of nature… and also for helping me get me up before the sun rose.

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Mensinger, M., 2018. Monitoring Nekton Biodiversity in Blackbird Creek. Report – submitted to the Delaware National Estuarine Research Reserve, Dover, Delaware.

Written by Jared Ryan, 2018 Environmental Education Intern.