The stock market came into the new week on a negative note, with the Dow Jones Industrial Average seeing the biggest declines among the major benchmarks. Renewed trade fears and political concerns out of Washington seemed to worry investors, and some trepidation about the speed with which interest rates have risen in recent days also weighed on some portions of the market. Yet some individual companies had good news that sent their shares higher despite the downbeat mood generally. Barrick Gold (GOLD -0.56%), Amarin (AMRN -2.22%), and California Resources (CRC) were among the best performers on the day. Here's why they did so well.

Barrick makes a buy

Shares of Barrick Gold climbed 5% after the company announced a huge acquisition that will create an even bigger player in the gold mining space. Barrick will acquire Randgold Resources in a deal that will pay Randgold shareholders 6.128 shares of Barrick for every Randgold share they own. Following the deal, Barrick shareholders will own almost exactly two-thirds of the combined company, with Randgold shareholders getting the remaining third. The merged company will be the largest gold-mining specialist in the world, and Barrick CEO John Thornton believes that it "will create a new champion for value creation in the gold mining industry."

Large gold bar with Barrick imprint.

Image source: Barrick Gold.

Amarin flies high on trial results

Amarin stock soared a whopping 316% in the wake of favorable clinical trial results for the company's prescription fish oil cardiovascular treatment. The biopharmaceutical specialist said that Vascepa successfully demonstrated roughly a 25% relative risk reduction in first occurrences of major adverse cardiovascular events, including death, stroke, and other indications. Vascepa also had favorable safety characteristics in the study. Having proved its naysayers wrong about whether a fish oil product could be effective, Amarin hopes to see a major expansion in revenue from Vascepa going forward.

Soaring oil lifts California Resources

Finally, shares of California Resources gained 18%. Monday was a strong day for the energy market overall, as global crude oil prices topped the $80-per-barrel mark. Domestically, crude prices are lower, in part because domestic producers still face challenges in getting their products from hard-to-reach fields to transportation hubs and refineries. With California Resources in particular remaining more highly leveraged than many of its peers, it makes sense that the stock is among the leading gainers across the oil and gas industry today.