OAKLAND -- Robberies and assaults rose 8.5 percent in a one-month period from July 13 to Aug. 13, a time when 80 police officers left the streets because of layoffs, according to statistics released Wednesday by the Oakland Police Officers Association.

Police brass and City Council members say that overall Part I Crime, which also includes homicide, rape, attempted rape, burglaries, larceny theft, arsons and motor vehicle thefts, is down 16 percent from 2009 to 2010 for the same one-month time period.

"One month is not enough time to determine a trend," said Deputy police Chief Jeffrey Israel, adding that he is still studying the numbers and plans to speak with the police union to find out where they got the figures.

City Councilmember Jean Quan agreed.

"You have to look at the year-to-date stats. It's the best way to gauge what's happening," she said. "It's way too early to tell."

In June, the City Council voted to lay off 80 police officers to help slash a $31 million budget deficit.

The Oakland Police Officers Association said there is a direct correlation between the rise in the two crime areas and decrease in officers on the streets.

"Crime in Oakland is up," said Dom Arotzarena, president of the officers' association. "Oakland police officers remain committed to doing the best job we can with the resources available, but the fact is, the 80 officers that were recently laid off patrolled our streets in Oakland. Their lack of presence is felt."

According to the current statistics obtained by the Tribune from Police Department analysts, 280 robberies were reported from June 13 to July 13. From July 13 to Aug. 13, they rose to 338 reported. From June 13 to July 13, there were 263 assaults, including shootings, reported. From July 13 to Aug. 13, there were 298 assaults reported.

"It's not beyond the realm of possibility that with fewer cops you have more crime. It's possibly that crime is up and it's up from losing 80 police officers," Israel said, adding that crime historically rises in the summer, often due to heat and more people out on the streets.

Other significant numbers were in burglaries and vehicle thefts. Burglaries actually dropped from 437 to 398 from June 13 to July 13, but rose to 436 reported from July 13 to Aug. 13. Vehicle thefts also dropped from 370 to 350 from June 13 to July 13, but jumped to 429 reported from July 13 to Aug. 13. Significant decreases were seen for the same periods in homicides, which fell 16.6 percent, and arsons, which dropped 17 percent, according to the officers' association.

Looking at a year-to-year comparison from 2009 to 2010 for the period July 13 to Aug. 13, robberies and assaults rose 13.5 percent.

Staff writers Cecily Burt and Kristin Bender contributed to this story.