By: Dr. Annamarie Hatcher
Fishing for striped bass (in Mi’kmaq: ji’kaw) in the Bras d’Or estuary was good between 2013 and 2017.
However, few were caught last year. The comings and goings of this popular sport fish in the Bras d’Or Lake Biosphere shape an interesting story.
The scientific name of the striped bass is Morone saxatalis. I don’t have much experience with this species, although I am well-acquainted with its first cousin, the misnamed white perch (in Mi’kmaq: sasqaji’j, scientific name: Morone americana) as a rewarding fighter on the end of a fishing line. So, I first consulted Skyler Jeddore, the official biosphere fish watcher, and Clifford Paul, from the Unama’ki Institute of Natural Resources, to learn more about striped bass in our biosphere.
The story of striped bass is confusing. They are found in fresh and salt water and everywhere in-between. The populations are loyal to specific sites but some of these sites don’t seem to be self-sustaining (no spawning has been observed). Many groups migrate but many don’t. Scientists report that they don’t feed when water temperatures dip below 10 degrees Celsius, but they are often caught by ice fishers on the Bras d’Or in mid-winter. Some fishers feel that their feeding can impact populations of young salmon but scientists have stated that these two species have successfully co-existed in our rivers since the Pleistocene. So, what do we actually know about the stripers in our biosphere?
Stripers are top carnivores. The large adult caught by Skyler Jeddore in August, 2014 had been eating a lot of moon snails and a large mackerel. The stomachs of 26 fish caught in the Bras d’Or late in 2015 contained mackerel, herring, silverside minnows, crabs, and shrimp (according to a study by the Bras d’Or Institute). Mackerel and alewife (gaspereau) seem to be preferred prey. Schools of large stripers can sometimes be seen during the summer chasing schools of mackerel near the wharf in Iona. In the spring, you may be able to see the large stripers chasing alewife near Castle Bay Beach in Eskasoni. Stripers caught under the winter ice on the Bras d’Or appear to be dining on silverside minnows. So, will increased numbers of this top predator impact the remaining salmon that call the Bras d’Or Lake Biosphere home?
Striped bass are native to the Maritimes. Stripers are an Atlantic coastal fish, found from northern Florida to the St. Lawrence River in many waterbodies ranging from fresh, to brackish, to salt. According to Leim and Scott in the book Fishes of the Atlantic Coast of Canada (Fisheries Research Board, 1966), the centre of the distribution in the 1960s was along the coast between Cape Cod and North Carolina. Currently, there are only two officially-recognized self-sustaining populations in the Maritimes, the Miramichi River in New Brunswick and the Shubenacadie River system on the mainland of Nova Scotia. In the past, there were two others in the St. John River of New Brunswick and the Annapolis River in Nova Scotia. They were extirpated (made locally extinct) due to multiple factors, including the installation of the causeway and tidal turbine in the Annapolis River, and the Mactaquac Dam in the St. John River.
Striped bass found on the west coast of Cape Breton are from a different population than those in the Bras d’Or estuary. Those west coast stripers are believed to be from the population which spawns in the Miramichi River of New Brunswick. They aren’t as large as the biosphere variety. Our stripers are believed to be from the spawning populations on the east coast of the United States. These populations are considered to be the source for many hotspots of abundance, such as the overwintering populations in Grand Lake and Minas Basin (mainland Nova Scotia), as well as the Bras d’Or estuary.
Many of the more southerly populations are migratory, and some very large individuals have made their way to the Bras d’Or estuary where they are often observed in late spring, coinciding with the gaspereau run. The majority seem to return south around the end of October. Anglers report that the best time to catch them in the Bras d’Or is late summer and fall. Although anglers catch the fish throughout the Bras d’Or estuary, stripers are most often found in areas such as coastal lagoons (barachois ponds) which are protected from waves, have high freshwater input, and an abundance of aquatic vegetation.
In fact, the large barachois pond in East Bay is a rewarding area to fish striped bass. In 2008, Cape Breton angler Christian Levatte caught a 57.9 pound striper in East Bay, a new Nova Scotia and Canadian record. Many species, such as gaspereau, are known to spawn in barachois ponds, and striped bass will feed on eggs, larvae, or juveniles. The most common areas for fishing stripers in the Bras d’Or estuary are the East Bay sand bar, West Bay, Dinah’s Pond, Middle River, McNabs Cove, and Nyanza Bay at the mouth of the Baddeck River.
So, what will happen to Bras d’Or stripers as ocean waters get warmer? In more southerly populations, it has been found that this species is very responsive to environmental temperature. In particular, the larger fish swim north just after spawning and feed in the cooler waters of estuaries along our coast. Because of rising ocean temperatures in recent years, migrating adults are moving further north and have recently made it to the coast of Labrador, a pleasant surprise for those anglers. Migration to the north after spawning puts the larger fish in an environment which is better for growth, avoiding the metabolic constraints of larger bodies in warmer waters.
According to a 2015 study in Virginia by Jody Callihan and her colleagues published in Marine and Coastal Fisheries, these migrations are more closely related to environmental temperature than are the runs of trout and salmon.
With the global rise in ocean temperatures, we can probably expect to see an increase in the numbers of large striped bass in the Bras d’Or estuary. However, will we expect to see establishment of spawners with a self-sustaining population? There have been reports of juvenile stripers from the Bras d’Or estuary and nearby ecosystems. However, our biosphere is outside of the geographic region of known spawning populations according to Colin Buhariwalla who did his Masters research on stripers in the nearby Mira River (Acadia University, 2018).
It appears that northerly striper populations such as the one in the Mira are quite different from their relatives to the south. Buhariwalla’s tagged fish stayed within the Mira. They did not migrate further afield. Similarly, none of the seven striped bass which were tagged and tracked in autumn 2013 in the Bras d’Or estuary by Allison McIsaac (Eskasoni Fish and Wildlife) and Bruce Hatcher (Bras d’Or Institute) ventured out into the Atlantic ocean.
There is little evidence that these Cape Breton populations are self-sustaining (spawning). So, where did they come from and will they spawn here in the future? These are questions that need to be answered if we are to manage this valuable fishery in our biosphere.
Dr. Annamarie Hatcher is a consulting ecologist and a board member of the Bras d’Or Lake Biosphere Reserve Association. Please share your striped bass observations with us on our Facebook pages (https://www.facebook.com/blbra/). For more information about the Bras d’Or Lake Biosphere Reserve Association, please visit http://blbra.ca/.