Recent headlines sound the warnings about a resurgence in gang violence:

The feds arrest local members of a notoriously violent Salvadorean gang, MS-13, which Portland police have said before-and still maintain-has not made significant inroads. Late-summer squawking about six downtown shootings gets loud enough for a gang summit convened by Mayor Tom Potter.

But the actual numbers for aggravated assaults with handguns (see chart)-a gauge police say is the best barometer for gang activity-show a downward trend.

Portland Police currently list 491 documented "gangsters," using the strictest definition of the term (usually admitting membership), though police estimate the true figure may be closer to 2,000. At gangs' apex in the mid-1990s, official police tallies topped 2,200.

Yet lest WW stand accused of minimizing a serious problem, here is a primer courtesy of Detective Peter Simpson of the Portland Police Bureau's gang unit on the city's most infamous crews, mostly black and Latino gangs, whom police do blame for much of the city's violent crime.

According to Simpson, local black gangs generally fall into two categories:

-Imports of Southern California gangs, like the Hoover Crips, from Los Angeles, or the West Side Pirus, from Compton, which open Portland satellites when members move north.

-Local spinoffs of larger gangs, like the Woodlawn Park Bloods or the Kerby Blocc Crips. These hometown upstarts formed in North and Northeast Portland neighborhoods, often in response to gangs from California.

Members and their crimes are scattered beyond Portland. "Our investigations take us from Longview, Wash., to Wilsonville," Simpson says.

The biggest difference separating gangs in Portland from those in bigger cities is turf. In Portland, a successful set rarely takes over an apartment complex, preferring instead to claim small businesses like barber shops and car washes for their deals.

Likewise, most gangs stay away from flashy, high-stakes-big-payoff crimes like armed robbery. Portland hoods are dabblers, moving from hustle to hustle, Simpson says, like "drug sales, prostitution, high-end identity theft, check fraud, counterfeit product sales."

Lately, Simpson says, "a lot of guys are converting from gangster to pimp," traveling with their girls from Portland to Las Vegas and back through California, a "traveling road show" that's been dubbed the West Coast Circuit.

Although a few local hoods stand out, Simpson says, there are no "man behind the curtain" masterminds.

Gang shootings, often at bars, get sparked by the same disputes, mostly over women, that have always sparked bar fights. Classic shoot-'em-ups tend to originate with Hispanic gangs, Simpson says.

Such violence from Latino gangs shows strength and helps to recruit members. Most members come from Sureño gangs (from Southern California), and belong to groups like Sur Trece Califas, 18th Street and Paso Robles Boys.

"We've had multiple cases where the suspects drive up, see a guy standing on a corner and ask him, 'What gang are you from?"' Simpson says. "And the victim will either say, 'I'm from 18th Street' or 'I'm not from a gang at all,' and they get shot and the guys drive away."