Bring a large pot of water to a boil over high heat; prepare an ice-water bath. Add salt to boiling water; return to a boil. Add fennel and cook until just tender, about 3 minutes. Drain and immediately transfer to ice-water bath to cool; drain and set aside.
Place lemon zest in a small saucepan and add enough water to cover. Place over medium high heat and bring to a boil; drain, return lemon zest to saucepan and repeat process twice more.
Place vinegar and sugar in a medium saucepan. Bring to a boil over medium heat, stirring occasionally, until sugar is dissolved. Remove from heat and add lemon zest; let steep for at least 10 minutes.
Slice the top and bottom of 2 oranges with a paring knife. Set one of the flat sides on your work surface. From top to bottom, following the curve of the fruit, cut away peel and white pith. Trim off any remaining pith. Holding the orange over a small saucepan, cut along both sides of each segment, staying close to the membrane, to release. Drizzle with olive oil and toss to combine; set aside.
In a medium skillet, bring orange juice to a boil over medium-high heat. Cook until thickened, about 3 minutes. Transfer to a medium heatproof bowl and drizzle with olive oil; set sauce aside.
Meanwhile, add just enough olive oil to coat bottom of nonstick skillet; place over high heat. When oil is hot, add fish and cook, turning once until opaque, about 7 minutes.
Heat a large dry skillet over medium-high heat. Add coriander seeds and toast until fragrant, 4 minutes. Remove from pan and crack slightly with the back of a spoon. Add to saucepan with orange segments and place over medium-low heat to warm.
Place fennel in a medium skillet; drizzle with olive oil. Add bay leaves and place over medium-low heat until warmed, about 2 minutes.
Divide fish and fennel evenly between 4 plates. Top fish with orange segments and steeped lemon zest; spoon over sauce. Garnish with cilantro. Serve immediately.