Ancient Events Shaped our Fisheries

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Don MacLean

I was asked the other day why we don’t have more species of freshwater fish in Nova Scotia. The person who asked me used to live in Ontario where they have many more species available to anglers. He wanted to know why we didn’t have species such as walleye, northern pike or muskies. The answer is based on geological, and climatic events which together have formed the aquatic environment we have today. Created by the collision of continents 400 million years ago, Nova Scotia has rocks which were once part of Africa, others from North America and some which resulted from the volcanic activity which occurred in the millions of years since.  The resulting mass of rock and lava cooled and, with the passage of millions of seasons, life came to the land. Then, 75,000 years ago, life and land forms disappeared as the province itself disappeared, under the weight of hundreds of meters of ice, not once, but four times. The last ice of the Wisconsin Glaciation retreated from Nova Scotia 12,000 years ago, a heartbeat of time in the time clock of the cosmos, and life began again.

Fish may have been the first to animals to return, swimming up rivers of glacial melt water from refuge areas farther South. These freshwater rivers soon retreated as the ice melted and the land rose, rebounding as the great weight of ice receded. Now almost surrounded by the sea the only freshwater fish in the province were the ones which had been able to colonize over glacial melt water. From now on only fish which could survive for a period of time in saltwater would be able to naturally colonize the lakes and rivers.

The legacy of this glacial history is a handful of fish species are found in our freshwater lakes and streams. Thirty-seven fish species are found in the province, and four of them, brown trout, rainbow trout, smallmouth bass and chain pickerel are late arrivals, the result of human intervention in the last one hundred years. This small species mix pales in comparison to the over 300 species of fish which are found in the coastal and marine waters of Nova Scotia.

While our freshwater fisheries may not have many species we have lots of place to fish them. “A wealth of wet” is how Gary Saunders describes Nova Scotia in his Ultimate Nature Guide to the province, and he is right. Although Nova Scotia is the smallest mainland province, with an area of 55,490square kilometers / (21,425 square miles,) it has 6674 lakes greater than a hectare in area. There are over 100 rivers and thousands of brooks.

Fresh water makes up 5 per cent of Nova Scotia’s surface area. That amount is not distributed evenly across the province. In central Nova Scotia lakes are scarce, but Pictou County anglers have hundreds of lakes to choose from. Most of our rivers are short, running as they do at right angles to the coast and many lack headwater lakes. As a result they run low in summer and early fall. Nova Scotia’s freshwater is a valuable resource for all of us and we need to pay special attention to ensure its supply for the future.

Don MacLean is an outdoor writer and biologist who lives in Pictou County.

 

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