The number of unlawful incursions by Spanish state vessels into British Gibraltar territorial waters rose last year compared to 2014.
But the number of serious incidents tailed off in the final months of 2015 against the context of diplomatic efforts to increase cooperation at sea.
Figures released by the Foreign and Commonwealth Office in response to Chronicle questions show that a total of 431 incursions were logged by British officials last year.
That compares to 387 in 2014 but is significantly lower than the 486 incursions recorded in 2013, when tensions at sea were running high.
The total for last year was pushed up by an intense period between May and August, when over 40 incursions per month were logged.
It was during this time too that a number of serious incidents unfolded at sea, including one in which Spanish customs officers fired warning shots close to a local pleasure boat.
That incident was described as “outrageous” by the British and Gibraltar governments at the time and led to diplomatic efforts to defuse tension and focus instead on cooperation.
The Royal Navy’s Gibraltar Squadron, together with the Royal Gibraltar Police, the Gibraltar Defence Police and HM Customs (Gibraltar), also stepped up their presence at sea as a deterrent.
Since then, officials said there had been “a noticeable decline” in the number of serious incursions.
Law enforcement agencies from both sides of the border have also cooperated in a number of anti-smuggling operations at sea.
Officials here caution against reading too much into monthly breakdowns on incursion numbers, which they said can be affected by weather conditions.
Likewise peaks in smuggling activity across the Strait of Gibraltar – and subsequent counter-smuggling operations – can also result in a rise in the number of incursions.
Number of incursions by month and year.
Source: Foreign and Commonwealth Office