"Every [clothing] retail chain that you see in your average shopping mall that sells clothing is importing them from China.
"So it's not a question of this one or that one, they are all affected by it."
The Cap Mondego was sent to Wellington to have its cargo shipped to Tauranga and then sent by rail to Auckland.
Stock was meant to be available from last Monday, but will not reach shops until about March 12.
One leading retailer paid an extra $10,000 to bring 12 containers of winter clothing by rail from Wellington. It was expected to arrive yesterday or today.
But Mr Silva said that option would not be available to those affected by future diversions because railways would become backlogged.
The rail link between Tauranga and Auckland - which relies at times on a single line - could become "unthinkable" by the third week of the strike, he said.
"There are hundreds of hundreds of containers on one of these ships. So even with the best rail in the world, these delays are going to begin to accumulate."
KiwiRail spokeswoman Jenni Austin said the operator was using available capacity to cope with an increase in volumes as a result of ship diversions to Tauranga and Wellington ports.
Asked if backlogs would be a concern in the coming weeks, Ms Austin said KiwiRail was working with the wider industry to respond as demand emerged.
"[We] are working with all our customers to do our part within the supply chain as best our capacity allows."
Rob Chemaly, general manager retail of Foodstuffs Auckland, confirmed the strike could affect the supply of some products, but would not reveal what those might be.
Progressive supermarkets spokesman Luke Schepen said goods had been diverted to other ports but would only say customers would not notice any difference in stores at the moment.
A spokeswoman for The Warehouse would not comment on disruption from the port dispute, and other retailers such as Briscoes and HallensteinGlasson did not respond to Herald inquiries.
Mr Silva said he understood that Auckland supermarkets could face shortages of packaged products arriving from Australia such as cereals, peanut butter, jam and chocolate.
He said retailers now kept "thin" supply chains where "typically the stuff for next week is arriving this week".
John Albertson, chief executive of the NZ Retailers' Association, said that with profit margins already squeezed, ultimately retailers would be forced to eventually pass on costs.
FROM PORT TO SHOP
* Winter clothing ranges will be delayed.
* Supermarkets expect shortages of some products.
* Extra transport costs expected to be passed on to shoppers.
* At least seven more ships are expected to be diverted before Monday.