Background
Many coastal fish in Massachusetts are commercially and recreationally targeted, and provide a number of economic benefits and ecosystem services. Examples of coastal fish in Massachusetts are:

• Bluefish
• Winter flounder
• Summer flounder
• Striped bass
• Black sea bass

Species such as winter flounder and striped bass are estuarine-dependent and spend a large portion of their lives in brackish water to spawn or feed ¹¹. Other species, like bluefish, will utilize estuaries as nursery habitat during juvenile stages ⁷. Some coastal fish make seasonal movements between estuaries and open ocean habitats throughout the year. Since coastal fish use several habitats while they mature, seasonal movements between inshore and offshore waters put them at risk to a range of human and climate stressors.

Direct Human Impacts
Exploitation of coastal fish communities can have detrimental ecological and economic consequences ⁶. For example, commercial fisheries target and remove the largest individuals from fish populations, which has led to populations with fewer size and age classes, and in some cases sparked evolutionary changes such as smaller, faster maturing fish ¹⁶. Faster maturing fish typically have reduced overall growth and reach smaller maximum sizes. In addition to directed harvest, many fishing practices unintentionally catch non-target species or portions of populations (known as bycatch), increasing the overall mortality rates these species experience.

Recreational fishing can also have significant impacts on fish communities if anglers harvest fish at higher rates than commercial fishers ¹. For example, the Atlantic States Marine Fisheries Council (ASMFC) recently reported that recreational harvest rates for striped bass, sea bass, bluefish, redfish, and tautog off the U.S. east coast were higher than those of commercial fisheries ^1,4. Best practices are being developed and implemented for catch and release fishing in many states to help reduce mortality ⁵. Because many coastal fish populations are already stressed due to high fishing pressure, their sustainable management under the increasing impacts of climate change will pose additional challenges to managers.

Climate Impacts
Climate change events such as increased temperatures, changes in hydrology, increased periods of drought, and sea level rise are already impacting coastal fish communities ⁹. Coastal fish that depend on estuaries for critical life stages, such as larval or juvenile growth and development, are particularly at risk. Climate impacts on coastal fish populations in Massachusetts and throughout their Atlantic range will vary based on access to suitable habitat, water quality, and local and regional rates of environmental change.

Fish have the ability to tolerate and adapt to climate change by shifting their behavior, distribution, and timing in certain habitats or for survival and reproduction ³. Nonetheless, many species rely on temperature cues for behaviors and activities such as migration, spawning, and growth. It is largely unknown exactly if and how many species will be able to adjust to the rapid rates of temperature, oceanographic, and subsequent ecological changes that have already been set in motion. Indeed, increasing sea surface and bottom temperatures have been shown to negatively impact the health and abundance of historically important and iconic New England fishes such as Atlantic salmon ¹⁷ and winter flounder ¹⁹.

Climate-induced shifts in salinity and stratification are also affecting the seasonal availability of primary (phytoplankton) and secondary (zooplankton) producers. These changes at lower levels of the food web have already impacted juvenile and forage fish communities with cascading effects that radiate to higher level coastal fishes and top predators ¹³. Diadromous fish (species that spend part of their life in salt water and part of it in fresh water), marine invertebrates, and some mollusks and crabs, are some of the most vulnerable to the impacts of climate change, which may have negative consequences for larger coastal fish that eat them ⁹.

In response to warmer water temperatures, many recreationally and commercially important fish species have already shifted their ranges northward or to deeper cooler waters, resulting in fish such as black sea bass and Atlantic croaker being found in places where they were once rare or not previously found ^{2,9,10,14,15,18}. Coastal fish that have already shown the greatest shifts in distribution tend to have shorter life cycles and smaller body sizes ^2,12. Hence, climate change and fishing pressure can have similar, and potentially compounding effects on fish populations that may interact in ways that are difficult to predict ².

In some cases, fishermen and fishing fleets have been unable to shift their harvest practices fast enough to keep pace with fish’s changing availability and seasonality due to regulations and socio-economic constraints ¹⁴. As fish species change when and where they are most abundant (and in some cases, new fisheries develop off Massachusetts), agile and adaptive management techniques should be practiced to maintain sustainable fisheries and enhance opportunities for fishing communities.