The CBL Seine Survey

            Working at Chesapeake Biological Lab (CBL), near the mouth of the Patuxent River, a lot of us tend to look out onto the water and wonder what kinds of animals are hanging out in our backyard. Luckily, some of us get the opportunity to regularly wade into the water to catch, count and measure the fish and invertebrates that inhabit the shallows around CBL’s research pier. For the past 16 years, Dr. Dave Secor’s lab has been conducting a seine survey in these waters once a week from May through October, where they document the abundance and size distributions of almost every species they catch. When the survey begins in early May, the water is typically just starting to warm up and fish and invertebrates are waking up after a long winter. The shallow habitat usually remains productive until mid-October, when the temperature begins to drop and many species move to deeper waters to overwinter. The survey is designed to include this period of warm temperature and peak abundance in the summer and fall, with the hope that the collection of species (also called an assemblage) that we observe over this time period can tell us something about how environmental conditions influence this assemblage each year.

Matt Siskey and Alex Atikinson of the Secor lab hauling in a big school of thrashing Atlantic menhaden caught in the seine survey

            Typically, many people expect that environmental conditions in the summer and fall, particularly the temperature, freshwater flow, salinity and wind will have the biggest influence on our summer-fall fish assemblage. Interestingly, that doesn’t appear to be the case. Winter conditions, especially temperature and flow, largely determine the species composition and abundance of the assemblage that we see in the subsequent summer and fall. In years with cool, wet winters (low temperature, high flow), we will typically see higher abundances of Atlantic silversides, Atlantic needlefish, juvenile striped bass and my personal favorite (see my earlier post), juvenile white perch. Conversely, in years with warmer and drier winters, we observe relatively high numbers of bluefish, spot, bay anchovy and northern pufferfish. The importance of winter conditions suggests that the productivity of the Patuxent River may be “preconditioned” during this time period, which would indirectly affect our fish assemblage. In addition, winter conditions can influence the timing of migration and reproduction in many fishes and invertebrates. These phenomena have been documented in other fish assemblages in other estuaries. However, these effects would have remained hidden in the Patuxent River if it weren’t for the CBL seine survey, started on a whim in the spring of 1999 and continued through the present day. It just goes to show how valuable this type of continuous monitoring can be for gaining insight, however small, into the processes affecting the animals in our backyard.

Dr. Dave Secor showing off some of our catch from the seine survey to passers-by.

            If you’re curious about the Secor Lab’s seine survey, you can find more information in this paper by Dr. Secor and his former technician, Becca Wingate. Or, you can follow us on twitter (@SecorLab), and look up some of our previous posts by searching #inseine!

This pretty fish, a young-of-the-year spotted seatrout is a rare find in the seine survey. We’ve only caught 13 individuals over the entire 16-year period!