The adjacent ports of Los Angeles and Long Beach, which compose the nation's busiest port complex, moved in different directions last month when it came to containerized cargo volume.

The Port of Long Beach reported last week that July cargo-container volume rose 18.4 percent from the same period in 2014 and was the strongest month in the facility's 104-year history. The Port of Los Angeles, meanwhile, reported a 2.5-percent decline in July compared to the year-earlier period.

After a slow start in 2015, due mostly to disruptions stemming from the 11-month contract battle between labor and management that bled into the New Year, Long Beach has gained momentum. In July, it moved 690,244 twenty-foot equivalent container units (TEUs). Imports rose 16.2 percent to 345,912 TEUs, while exports rose 15.9 percent to 143,875 TEUs, Long Beach said. The balance was composed of the movements of empty containers, which are included in the total volume figures.

At Los Angeles, the nation's busiest port, total traffic in July hit 699,127 TEUs. Imports decreased 3.5 percent, to 350,627 TEUs, in July 2015, from 363,393 TEUs in July 2014. Exports declined 16.4 percent, to 136,402 TEUs from 163,294 TEUs in July 2014 Combined, total loaded imports and exports at Los Angeles decreased 7.5 percent, to 487,029 TEUs, compared to 526,688 TEUs in July 2014. The overall 2.5-percent year-over-year decline factors in the movement of empty containers, which increased 11.2 percent year-over-year.

Officials at both ports said the diverging fortunes in July were due to more vessels involved in ship alliances calling at Long Beach than at Los Angeles. Ben Hackett, head of a maritime consultancy that bears his name, agreed with those comments and said it doesn't reflect on the competitive positions of the ports. "There is nothing significant in the up/down here," he said in an e-mail today.