Heat oil in a saucepan over medium heat. Add onion; saute until translucent, about 3 minutes. Add potatoes and carrots; saute until starting to soften, about 5 minutes. Pour in fish stock and bring to a boil. Add shrimp bouillon. Reduce heat and simmer until vegetables are soft, about 10 minutes. Add shrimp; cook until bright pink on the outside and the meat is opaque, about 5 minutes. Season with salt. Serve hot with lime wedges and jalapenos.