Melt butter with olive oil in heavy large skillet over medium heat. Add shallots and garlic; sauté 3 minutes. Add tomatoes and cook just until tender, about 5 minutes. Increase heat to medium-high. Add wine, clam juice, lemon juice and marjoram; simmer 5 minutes. Add salmon and simmer until almost cooked through, stirring occasionally, about 5 minutes. Add arugula, capers and fresh herbs to salmon mixture. Simmer until salmon is just cooked through and arugula is just wilted, about 2 minutes. Season to taste with salt and pepper.
Meanwhile, cook linguine in large pot of boiling salted water until tender but still firm to bite, stirring occasionally.
Drain pasta well and return to pot. Add salmon-arugula mixture to pasta and toss to coat. Serve warm.
