Whether or not you knew what day it was (or even month), May 1st was the start of the striped bass fishing season in Maryland. This year, the fishery is a bit different though and not just because of the COVID-19 pandemic.
Like most fisheries, the striped bass fishery is managed by a number of groups including the Atlantic States Marine Fisheries Commission (ASMFC) and the Maryland Department of Natural Resources. Management decisions are based upon regular stock assessments which look at how many fish are being caught, the number of female fish that are estimated to be spawning (Female Spawning Stock Biomass = SSB), and the number of fish being killed by the fishery (Fishing Mortality Rate = F). The last two numbers are important because there are certain thresholds set and if we go over those thresholds, it means the fishery may collapse because there aren’t enough fish to replace the ones that are being harvested.
The striped bass stock assessment for 2018 said that over fishing is occurring in the Chesapeake Bay striped bass fishery, which has prompted some major changes to catch limits and fishing seasons. At first glance, it seems odd that striped bass in the Chesapeake Bay are over fished since the average yearly catch has been decreasing since approximately 2014 and we’ve already seen some changes to recreational fishery in the last few years. However, there are a couple of reasons as to why over fishing is occurring.
Striped bass have what is known as a slot size limit. This means that you are allowed to keep fish within a certain size range, so there is a minimum size and a maximum size that you can keep, depending on the season. This type of regulation is not arbitrary; it has to do with the fact that for many fish species, larger female fish are more successful in producing offspring. That means that these bigger females produce more offspring that are more likely to survive. In the case of striped bass specifically, larger females produce eggs that are larger, have more nutrients, and are more likely to hatch and that the larvae from these eggs are larger and more likely to survive (Zastrow et al. 1989). Because managers want to make sure there are enough of these larger fish to produce lots of healthy babies, they put maximum size limits in place.
However, the problem with these slot size limits is that it encourages a catch and release fishery. While not inherently a bad thing, there will always be a proportion of the fish that die shortly after they are released. This is because being caught can be pretty stressful for the fish. Currently, the Atlantic States Marine Fisheries Commission assumes that approximately 9% of all striped bass that are released after being caught, die. This estimate was based on research that looked at mortality rates in saltwater and found that anywhere from 3% to 26% of released fish died, depending on conditions like water temperature (Diodati and Richards, 1996). Regardless, because people are only able to keep fish within a specific size slot, any fish that is too small or too big must be thrown back.
This is significant because the striped bass fishery is dominated by recreational catch, where catch is managed by the slot size limit. According to the ASMFC, in 2015, 68% of all fish caught were caught recreationally which made up 79% of the total weight of fish harvested that year (http://www.asmfc.org/uploads/file/57b22f6dsbfmpreview2016.pdf). The 2018 assessment estimated that approximately 33.7 million striped bass were caught recreationally in 2018 with 2.2 million fish actually being kept (harvested) and the rest being thrown back. Based on that 9% release mortality, 2.8 million of those fish that were thrown back were estimated to have died. While the actual number of dead fish depends on things like how long the fish were out of water, whether it was a warm day or a cool day, and what type of hook was used, there were potentially more fish that were thrown back and died than were harvested.
The Maryland Department of Natural Resources is aware that there may be a lot of fish dying after being released, which is why a number of changes have occurred in recent years. These include lowering the slot size minimum from 20 inches to 19 inches (so that more fish that are caught can be kept) and requiring the use of circle hooks in some situations (since they hook fish in spots that are less physically damaging to the fish). They are also trying to educate anglers on the conditions that reduce the survival of released fish, such as when air and water temperatures are high. You can read more about the current regulations and why they are being used here: https://news.maryland.gov/dnr/2020/02/12/striped-bass-conservation-regulations-set-for-spring-2020/.
In addition to catch and release mortality, there was also a period of low recruitment from 2005 to 2011. This means that we had relatively low numbers of fish making it through their first year of life in this time period, which is currently affecting the number of larger fish in the Chesapeake Bay. For fish like the striped bass, they keep growing throughout their lives, so we can use size to estimate age. A fish that was hatched in 2005 would be approximately 44 to 45 inches right now, while a fish that was hatched in 2011 is approximately 33 to 34 inches. At the current minimum size (35 inches for May 1st through May 15th), you are catching fish that hatched in 2010 or before, possibly during this period of low recruitment. This means there likely aren’t too many fish in this size range, so we may see relatively low recreational catch this year, at least until the slot size limits take effect later in the year. It also means that in the next few years, we should start seeing fish from high recruitment years like 2012, 2015, and 2016 reach maturity and begin reproducing. If enough of these fish have survived, some of these new regulations may be relaxed in a few years.
Ultimately, the goal of fisheries management is to ensure that there are enough fish to reproduce and replace the ones we are removing, including the ones killed from catch and release fishing. We all want to see the recreational striped bass fishery continue so we have to do our part to minimize the mortality of unwanted fish. For those of us who support fisheries by eating fish, do your homework on what methods of catching striped bass, and other fish, are more sustainable. According to the Monterey Bay Aquarium Seafood Watch https://www.seafoodwatch.org/seafood-recommendations/groups/bass).
Diodati, P. J., & Richards, R. A. (1996). Mortality of striped bass hooked and released in salt water. Transactions of the American Fisheries Society, 125(2), 300-307.
Zastrow, C. E., Houde, E. D., & Saunders, E. H. (1989). Quality of striped bass (Morone saxatilis) eggs in relation to river source and female weight. Rapports et Procès-verbaux des Réunions, Conseil International pour l’Exploration de la Mer, 191, 34-42.
________ Dr. Kristen Lycett PhD
Phillips Wharf Fishmobile Coordinator
Phillips Wharf’s newest staff member and marine estuarine scientist Dr. Kristen Lycett fills the role of Fishmobile Coordinator. She is currently on loan to us from Americorps until August when we hope to secure her full time. Lycett received her Ph.D. from the Marine Estuarine Environmental Science program at the University of Maryland Eastern Shore, where she studied the parasite Hematodinium perezi, which infects blue crabs and other crustaceans.