Marine Biology

Time of collection

Unlike some of tideless seas like Mediterranean, the seas that lap Indian shores have tides which may range from a fraction of metre to prodigious 6 ½ m as in Gulf of Cambay. There are two high tides and two ebb tides in 24 hours. Both high and ebb tides occur roughly 50 minutes later each day i.e. tides in our country are predominantly semidiurnal. At new moon and full moon, the sea water rises unusually high and receeds unusually low; these are called spring tides. During the first and last quarters of the moon , we have neaptides, when the sea water neither comes up very high nor receeds very low; obviously it is preferable to visit the seashore at the time of spring low tides, when the maximum portion of the shore is exposed.

On our shores, the monsoon is so vigorous that a good part of our shore life in the intertidal region gets washed away or dies due to the lowering of salinity arising out of  dilution by rain water. It is futile  to seek a variety of shore life during  this season. On  cessation of the monsoonal rains,  marine life starts to colonize the intertidal region and grows to maximum abundance in winter. After  winter, the increasing warmth starts to affect shore life, so that it starts to decline and is washed off once again during  the rainy season. The best time of year for observing and collecting intertidal life is therefore during winter preferably late winter.