This week we have a piece written by a pair of Mass Maritime Academy students who are spending their winter break with us. Cadet Michael Kerrigan is a Junior at the Academy and is fulfilling his co-op requirement here at the Landing. Cadet Holly McLaughlin is a freshman who is volunteering to help us out. Enjoy…
Many rivers and streams are nurseries to different juvenile fish. The reason for this is because they provide protection from predators and provide ideal spawning grounds. Some of these areas can be strictly salt or fresh water flowing, but some are a mixture of both. These areas are commonly known as estuaries. An estuary is a transition zone from where freshwater flows to seawater. This prevents predators from going up these types of rivers and streams because their bodies can’t handle the transition of salinity. These types of rivers are very significant because problems continue to grow along them and affect wildlife, specifically populations of spawning fish such as river herring.
River herring are migratory fish that travel in various amounts known as schools. There are normally two fish species linked together when using the term river herring, Alewife (Alosa psuedoharengus) and Blueback herring (Alosa aestivalis). Alewives can live up to 10 years, grow as large as 36cm, and spawn in early spring when water temperatures are between 60F (16C) and 66F (19C). While blueback herring live up to 8 years, grow up to 40cm, and spawn a little later than Alewives in spring when water temperatures are between 70F (21 C) and 75F (24C) .They are both also anadromous fish, which means they are one of the many types of fish that travel up rivers or streams to spawn and then travel out to sea. Although this process seems fairly simple, in some cases it isn’t. River herring face many obstacles between the ocean and their spawning grounds causing a continual decline in population .Most herring return to their natal spawning ground, but due to various human activity, they can not reach their destination. This includes, but is not limited to the water quality of the area, over fishing and bycatches, and loss of habitat. All of these factors can be related to anyone living on or near a river.
There are many contributions that can cause a decline in water quality. Along rivers there are recreational activities, houses, and businesses, which all effect the condition of the water. Among some of the recreational activities are boaters, which can be seen as a contributor to water pollution. A lot of boating activity in an area constitutes a problem as well because the river is faced with constant engine idling, harmful bilge pump outs, and oil or gas spills and leaks. Also, many boaters have small portable toilet systems and do not take the proper measures to go to a pump out station as directed. Instead many pump them directly overboard with no treatment leaving sewerage in the area. Houses along the river can be a cause of sewerage infiltrating the river as well. Many of the houses in the area have septic systems with leaching fields. Leaching field discharge often finds its way to bodies of water. Also, when the river has high tides it can flood septic systems and pull back pollution as the tide retreats. Even with homes that had septic systems that have recently connected to the sewerage line can still pose problems. This is because although the system isn’t geting anything put into it the leaching fields are still discharging and the soils around them take time to be flushed out. Also, homes around the river have sediment runoff into it. All runoff is, is when it rains or water is applied to a surface it will find low points normally leading to a river or stream and carry material with and substances with it. With homes this can cause problems because many people apply lawn fertilizer, pesticides, and have fluids leaking out of there cars. All of these substances can eventually make there way through runoff to a stream or river. Some businesses produce water pollution as well because they are allowed to discharge small amounts into rivers causing further contamination. All of these factors contribute to water quality. The fish cannot return in order to spawn if the water is not clean enough.
River herring are an easy species to be targeted as bycatch. This is because they travel in schools that can be made up of large numbers. As they move closer to there spawning grounds they become more confined as the river narrows, making them an easier target for fishermen. Besides just river herring which go upstream to spawn, there is also the Atlantic Herring (Clupea Harengus) which are strictly marine fish which have some restrictions on harvesting but not a total closure to the fishery. This is where most of the bycatch takes place and the fish are taken. River Herring have harvesting bans which restrict fishermen from catching them. River Herring populations have been drastically decreasing. For example, fishery landings have declined from 40,000 tons in the 1950s to less than 3,500 tons in 2005 (FAO, 2007). This is why rather than being a targeted species, they are often bycatch, getting caught in gear such as gillnets and midwater trawls.
In the early 1900’s, as industry grew, the more people harvested hydro power off of rivers for convenience in factories. With many of these factories gone, still standing dams are left behind. This interrupts the natural flow of the river as well as the habitat of everything that lives in or around the area. Dams make it impossible for the herring to migrate back to their original spawning grounds. Although some actions have been taken to allow fish to pass, there is still no solution to the problem. Fish ladders are one of the solutions, but they do not solve the problem because fish can be too weak to swim up or locate them. If fish ladders are present and hydro power is being generated, they still pose a threat for many reasons. Herring are a velocity species, which will cause them to swim closer to the turbines. As they get closer to the turbines, they will be in the tail race where over oxidization of the water occurs. The herring may also swim up into the
turbine discharge tube, which will either kill them or lead them to a dead end. Some actions put into place are installing metal screens, so the fish don’t have access to these areas, but they are not very reliable.
The obstacles that the river herring population face can be prevented. Many of these problems can be addressed with simple procedures. For instance, in boating aspects, funnels can be used to avoid spillage, safer chemicals can be used when cleaning, and catching bilge water while discharging can be helpful. To address the septic system problems, connecting to the town sewerage would be ideal. When doing any yard work or maintenance be cautious of any harmful chemicals used or put down and also check your cars periodically for leaks or drips that could be going onto the ground. Although the cost is high, dam removal would be an great solution for dams that are nonfunctional. Most obstacles river herring face can be eased and if we all do our part we can help rebuild their population.