James Fisher warned that first-half results would be lower than last year after its offshore oil arm suffered a "slow start" to 2015.The industrial support services group said it expected to see a stronger second half as performance improved at its Marine Services divisions.Shares in the FTSE 250 group were down 8.5% at 09:30 but gained ground as analysts' positivity on the stock spread.Panmure Gordon said the trading update "looks fine" and Investec "broadly on track", both maintaining their positive ratings.The offshore oil division has felt the force of the major restructuring by oil companies, leading to a first quarter that was weaker than was anticipated and weaker than last year when it had been boosted by large one-off contracts in Brazil.The marine support and specialist technical divisions made good progress, while tankships continued on its positive course.In particular, marine support saw some recent improvement in ship-to-ship volumes and management said it expected to see an increase in project revenues, particularly in the second half.Specialist technical continues to make good progress with the delivery of its strong order book and is "well positioned" on a number of significant contract bids.House broker house broker N+1Singer has slightly reduced pre-tax profit forecasts, by 4%, to reflect this but remained confident that the second half will see an improvement, highlighting the company's positioning in "niche areas which can continue to grow despite tough current market conditions".