LAURA did not know whether to laugh or cry. 'Herschel have put us ecologically sensitive folks in a great quandary', my Seattle host murmured anxiously. Fortunately, Laura is a tree-hugger with a sense of humour: 'I know that sounds like a contradiction in terms,' she admitted. To prove it, she grinned at Herschel. Beside the locks of Lake Washington Canal, neither Laura nor any other day-tripping Seattleite could tell me why a gang of sleek sea-lions had been dubbed 'Herschel'. All everybody knew was that the sea-lions had provoked a love-hate complex among nature-loving citizens of Washington State. The issue was clear: should Herschel be allowed to cock a collective whiskered snook at mankind's well-meant efforts to help other marine creatures? The issue focused on the Fish Ladder beside Lake Washington Ship Canal. Built and maintained by the US Army's Corps of Engineers, like the waterway itself, the intricate Fish Ladder originally opened in 1917 with 10 steps. Reconstructed in 1976 for US$2.3 million (HK$18 million), the 'ladder' now has 21 steps designed to help fish by-pass the canal's lock system. Eight decades ago, the canal - and the consequent damming of Lake Union - was an essential boost for Seattle's economy. It enabled faster shipment of timber and goods from inland regions to the Pacific Ocean via Lake Washington, Lake Union and Salmon Bay. Today, the canal is also a favoured short-cut for pleasure craft. Its two locks handle 80,000 boats a year, including Alaska-bound container vessels, log rafts and fishing boats. Only a 30-minute bus-ride from downtown Seattle, the Hiram M. Chittenden Locks (named after the military major who engineered them) are a popular day-tripping destination. They are the heart of a lovingly-landscaped, English-style botanical garden sporting more than 500 species of trees and flowering shrubs, waterside promenades, and a Visitor Centre housed in the project's original blacksmithy-cum-carpentry shop. The canal system, manned by 60 personnel, is good evidence of the army's peacetime usefulness. The military's early 20th century ecological concern is manifest in the Fish Ladder's viewing gallery. There, most months of the year, visitors marvel at the sight of salmon and trout surging upstream via the ladder's 21 graduated 'steps', which consist of small weirs. The underwater viewing gallery's illuminated windows gaze at the elongated 18th step. In the second half of the year, it mainly reveals a salmon run, with peak migratory months of July, August and September for sockeye, chinook and coho species. Cutthroat trout share the run from August to February, bunching up in November for their trip to upstream spawning areas. Around the same time, Steelhead trout begin lining up for the run, reaching their peak in January and tailing off in April. During the upstream migration periods, it is an underwater eye-opener to spy huge mature fish leaping the steps, driven by genetic urges to power their way uphill through cascades of water. With each step, the fish re-acclimatise to fresh water. At other times of the migratory year, young fish can be seen heading downstream to Puget Sound and the open sea. On the surface, and below it, everything seems handsomely arranged for the migrants by the Corps of Engineers. The damming of the lake having deprived the fish of their natural runs, they were given a man-made replica. But then Herschel appeared on the scene. At first, modern legend tells, Herschel was a solitary sea-lion who wandered into Puget Sound and found himself surrounded by juicy hunks of live salmon all heading in the same direction. Herschel could not believe his luck. All he had to do was swim around the bottom of the Fish Ladder, waiting for the juicy hunks to leap into his mouth. Seattle's fish-huggers were horrified. It might be acceptably natural for grizzly bears to ambush fish beside mountain rapids, but it was very unsporting of Herschel to take advantage of a man-made conservation effort. 'We couldn't shoot him, could we?', Laura recalled. 'The Engineers tried shooing him away, scaring him with explosions, even jeering him. Nothing worked, so they caught him and shipped him off to a marine park in California.' Within weeks, two new sea-lions had sniffed out the feast. When a third sea-lion appeared, resembling the original interloper, Seattle assumed Herschel had dashed back from California. He was now a favourite anti-hero, and the ecologically-sensitive were alarmed that the gang of villains would multiply. The day I saw Herschel, I knew I had never seen three fatter sea-lions. Being a salmon addict myself, I could not help admiring their graceful gourmandising. Coming up for air between salmon mouthfuls, they lounged in the bubbling waters below the dam, seeming to bob and wave at the humans lining the lock walls. 'It has been known for spectators to cheer them,' Laura noted, confessing her hate-love complex. Meanwhile, back at the main lock's downstream gate, salmon were holding a mass demonstration. They literally filled the surface of the lock's access channel, awaiting their chance to slip into the arms of the lock and be lifted upstream, away from Herschel. On the other side of the lock, up in the lake's fresh water, escaped salmon leapt out of the water, free of the clutches of Herschel. 'What are we supposed to do?' Laura sighed. 'Our youngsters are supposed to be watching the marvel of fish leaping up a marine ladder. Instead, they are seeing harsher laws of nature at play outside the ladder.' She now takes her children to the locks primarily to watch the boats going up and down. One day, she hopes, her children will tell her how to cope with Herschel.