compared to the comparable 13-week period of fiscal year 2021. Within the hunting and shooting department, our firearm category saw a decrease of $8.8 million or 9.9%, while our ammunition category saw an increase of $7.6 million or 13.9% in the first quarter of fiscal year 2022 compared to the comparable 13-week period of fiscal year 2021. The decrease seen in the firearm category is primarily due to lower demand as we anniversaried the increased demand during the first quarter of fiscal 2021 driven by the COVID-19 economic stimulus package (the American Rescue Plan) and social unrest, partially offset by the opening of 13 new stores since May 1, 2021. The increase in the ammunition category is due to improvements in the supply chain disruptions seen in this category over the past two fiscal years as well as the opening of 13 new stores since May 1, 2021.
With respect to same store sales, during the 13 weeks ended April 30, 2022, our fishing, optics, electronics and accessories, camping, hunting and shooting, footwear and apparel departments saw decreases of 19.4%, 15.7%, 14.9%, 10.0%, 6.7% and 4.4%, respectively, as we anniversaried the increased demand during the first quarter of fiscal 2021 driven by the COVID-19 economic stimulus package (the American Rescue Plan) and social unrest. As of April 30, 2022, we had 113 stores included in our same store sales calculation.
Gross Profit. Gross profit decreased to $99.1 million during the 13 weeks ended April 30, 2022 compared to $104.0 million for the corresponding period of fiscal year 2021. As a percentage of net sales, gross profit increased to 32.0% for the 13 weeks ended April 30, 2022, compared to 31.8% for the corresponding period of fiscal year 2021 primarily driven by favorable product sales mix and increased product margins across most departments, partially offset by higher freight costs. We expect higher transportation costs to continue to impact the business during the remainder of fiscal 2022 and beyond.
Selling, General, and Administrative Expenses. Selling, general, and administrative expenses increased by $5.7 million, or 6.3%, to $96.1 million during the 13 weeks ended April 30, 2022 from $90.4 million for the comparable 13-week period of fiscal year 2021. This increase was primarily due to an increase in other selling, general and administrative expenses of $4.5 million, which was largely the result of a return to pre-pandemic levels of marketing and travel activities compared to the comparable 13-week period of fiscal 2021. We also had increased pre-opening expenses of $0.8 million due to the timing of opening new stores, as well as increases in depreciation, payroll and rent of $1.6 million, $0.8 million, $0.6 million, respectively, during the 13 weeks ended April 30, 2022 primarily related to the opening of 13 new stores since May 1, 2021. These increases were offset by a decrease in acquisition costs of $2.8 million due to the terminated merger with Great Outdoors Group. As a percentage of net sales, selling, general, and administrative expenses increased to 31.0% of net sales in the first quarter of fiscal year 2022, compared to 27.7% of net sales in the first quarter of fiscal year 2021, due to the same reasons disclosed for the increase in selling, general, and administrative expenses.
Interest Expense. Interest expense increased by $0.4 million, or 200.0%, to $0.6 million during the 13 weeks ended April 30, 2022 from $0.2 million for the comparable 13-week period of fiscal year 2021. Interest expense increased primarily as a result of increased borrowings on our revolving credit facility during the first quarter of fiscal year 2022 compared to the first quarter of fiscal year 2021.
Income Taxes. We recognized income tax expense of $0.4 million during the 13 weeks ended April 30, 2022 compared to an income tax expense of $3.0 million during the comparable 13-week period of fiscal year 2021. Our effective tax rates for the 13 weeks ended April 30, 2022 and May 1, 2021 were 18.1% and 22.0%, respectively. Our effective tax rate will generally differ from the U.S. Federal statutory rate of 21.0%, due to state taxes, permanent items, and discrete items relating to stock award deductions.
Seasonality
Due to the openings of hunting season across the country and consumers’ holiday buying patterns, net sales are typically higher in the third and fourth fiscal quarters than in the first and second fiscal quarters. We also incur additional expenses in the third and fourth fiscal quarters due to higher sales volume and increased staffing in our stores. We anticipate that our net sales will continue to reflect this seasonal pattern.
The timing of our new retail store openings also may have an impact on our quarterly results. First, we incur certain non-recurring expenses related to opening each new retail store, which are expensed as they are incurred. Second, most store expenses generally vary proportionately with net sales, but there is also a fixed cost component, which includes occupancy costs. These fixed costs typically result in lower store profitability during the initial period after a new retail