In legal circles, a 'fishing expedition' is an illegal attempt to discover unspecified information which may, perhaps, be prejudicial to one party in a legal case. It is illegal because just about everybody has things in their possession which might be evidence of breach of some law or other - however trivial, archaic or obscure.
Currently in the news1 is the fact that wildlife biologist Charles Monnett is under investigation by the office of the inspector general at the US department of the interior. News stories have reported that the investigation concerns a study2 of polar bear deaths.
The Sacramento Bee now reports as follows:
A federal official says the suspension of Alaska wildlife biologist Charles Monnett is unrelated to a 2006 article Monnett wrote about presumably drowned Arctic polar bears.
A watchdog group said questioning by investigators centered on the polar bear observations but that Monnett hasn't been informed of the specific allegations being investigated.
The Sacramento Bee
If investigators of any variety came to my house to search it or to question me - without specifying the reason - I would have two words for them. I apologize for my bluntness, but the 2nd word would be 'off' and the 1st would begin with F.
A person is entitled to the maximum feasible time in which to prepare a defense against any charges. This means that he or he is entitled to know - from the very outset - what matter is being investigated.
It may be that a person who is informed about the matter being investigated will produce evidence forthwith - for or against the matter - and so save a great waste of time and expense on both sides.
If it turns out that Monnett is being persecuted for being a scientist, then his legal advisers would do well to cite papers3 published before and after the one in question. They would also do well to cite Judge Easterbrook -
"Scientific controversies must be settled by the methods of science rather than by the methods of litigation. … More papers, more discussion, better data, and more satisfactory models – not larger awards of damages – mark the path towards superior understanding of the world around us."
Underwager v Salter 22 Fed. 3d 730 (1994)
 - news articles
 - Monnett and Gleason paper
Observations of mortality associated with extended open-water swimming by polar bears in the Alaskan Beaufort Sea
Charles Monnett and Jeffrey S. Gleason
 - example of related papers
Possible Impacts of Climatic Warming on Polar Bears
Ian Stirling, Andrew E. Derocher
Polar Bears in a Warming Climate
Andrew E. Derocher, Nicholas J. Lunn and Ian Stirling