MY VERSION of walking the dog is to put the canine, whose name is Harley, into the car and drive to the nearest boat ramp.

The normal procedure is to park the car, get Harley out and head past the cleaning tables.

However, like all dogs, Harley is a sniffer, and if he is unsure of what it is he is sniffing then he will invariably taste it, which is fine except for the undersize sand flathead carcasses, discarded bait and indiscriminate dumping of native starfish.

The flotsam of grubby anglers is a problem for dogs, people and, I would suggest, the sustainability of some bay species, like sand flathead and native starfish.

First to sand flathead: The population of this once prolific bay fish is in serious decline in Port Phillip Bay. We cannot afford to waste what is left.

A Baywide Port Phillip Bay Annual Trawl Sub-program report released in August by Fisheries Victoria shows that there has been a decline of about 93 per cent in sand flathead numbers since the early 1970s, when the species was already recognised as being in decline.

The reports states: "Changes in sand flathead abundance and biomass in the period 2008-09 were outside of expected variability.

"These changes reflect an on-going trend that can be traced to the mid 1960s.

"Recruitment failure appears to be driving the recent decline in sand flathead abundance in the bay.

"The reasons for this recruitment failure and the ecological significance of declining sand flathead abundance in (the bay) are not known."

There you have it.

If you had to name the easiest and most commonly caught saltwater species in Victorian waters, the chances are the first fish that would come to mind is the flathead. I cannot remember anyone ever complaining about the lack of flathead.

But the times are changing.

Sand flathead populations in Port Phillip first appeared to decline in the mid 1960s.

Fisheries researchers attributed the decrease in sand flathead between the early 1970s and 1990 to fishing pressure.

Since 1990, the abundance of sand flathead continued to diminish further.

The most recent report states that the abundance of sand flathead in the bay was significantly lower after 2007.

During the 1990s, there were concerns that both numbers and size of sand flathead had decreased.

These concerns prompted Marine and Freshwater Research Institute researchers to examine the population dynamics of sand flathead in Port Phillip Bay.

To gain basic biological information, the age of many thousands of fish was determined by examining growth rings on their ear bones.

The data has revealed that sand flathead live for a lot longer than previously thought.

The maximum estimated age for sand flathead is 23 years old.

MAFRI research found that the growth of sand flathead was highly variable, meaning that big fish are not necessary old fish.

The study revealed that a seven-year-old female sand flathead could be anything between 22 and 37cm long, and that female sand flathead measuring 30cm could be between three and 23 years old.

The size of sand flathead is influenced by its sex. Female sand flathead are larger on average than male sand flathead.

Average size of male and female flathead were 23cm and 25cm respectively.

The minimum legal size limit for sand flathead is 27cm.

Another problem is with identification of seastars, or starfish as most people call them. There are many native species of seastars in Port Phillip Bay.

The brownish yellow zigzag seastar has five arms with blunt rounded tips and a zigzag pattern down the centre of each arm.

The native, eleven-armed seastar is brown or blue-grey and has large well-spaced spines.

The villain of the bay and a serious pest is the Northern Pacific seastar.

It has five arms with distinctive pointed upturned tips.

It is mainly yellow in colour with purple details and the arms are covered with many small spines and jagged ends.

At the boat ramp I see many native seastars, brought in and dumped by perhaps well-meaning anglers who have wrongly identified them as the Northern Pacific variety.

There is no sense killing the local seastars, and the Northern Pacific seastars should be brought to shore and put in an appropriate rubbish bin.