Preferred Habitat of Alope Spinifrons

Abstract This investigation examined the preferred habitat of the prawn Alope spinifrons for the purpose of keeping the prawn in optimum conditions in captivity. The survey took place on shoreline between Matapouri Bay and Wooleys' Bay on the Tutukaka Coast. A. spinifrons populations were surveyed, water chemistry, temperature and depth were noted as well as substrate type and flora and fauna sharing the area. A. spinifrons preferred sheltered rocky areas where there was good water circulation and a water level at MLWS deep enough to prevent desiccation. Because of their social structure A. spinifrons preferred areas where other individuals had already settled.

Introduction The species Alope spinifrons is a Heavy built shrimp found on the coastline throughout New Zealand. It has a green translucent body with longitudinal red stripes and carapace reaches 16mm in length (Morton, Miller 1968). Usually found beneath rocks or in crevasses in the sub littoral zone. The species is a good specimen for the aquarium because of its social interactions bright colours and scavenging diet but appears to be sensitive to abiotic factors. The purpose of this survey is to identify the preferred habitat of A. spinifrons so that it can be kept in captivity successfully.

Methods The survey was conducted on the 15th and 16th of May, 2003. At Mean Low Water Spring (MLWS). Along the coast from Wooleys' Bay to The north end of Matapouri Bay, on the Tutukaka Coast. Four separate populations of Alope spinifrons were located by walking the length of coast, all rock pools and mobile rocks, boulders and cervices were inspected. The four populations were then surveyed.

Once an area was identified to contain A. spinifrons it was photographed, Exposure and substrate was noted. The area was then systematically searched by lifting rocks and taking note of flora and fauna that shared the rock with A. spinifrons.

The rocks were lifted from the survey facing area edge towards the outside edge. This was done to discourage escaping individuals from fleeing into the un-surveyed area. Rocks were lifted completely out of the water slowly to minimize disturbing the area.

Ammonia presence, pH, temperature and specific gravity were taken from water.

Results The Whale Bay, habitat was a tidal pool that was isolated from the ocean at MLWS, the substrate was shell gravel made up from the Rock Oyster's (Crassostrea glomerata ) that inhabit the surrounding rocks. The pool contained no macro algae. Alope spinifrons were distributed between Four Shell encrusted rocks (Fig 1.0) that were partially submerged in 100mm of water. The underside of the rocks was bare of shells and provided shelter for several animals including A. spinifrons; these were Actina tenbrosa, Ischnochiton maorianus and Diplocrepis puniceus. The substrate beneath the rock did not contain organic matter and was home to Opinonereis fasciatus and Petrolisthes elongates. The largest numbers of A. spinifrons were located on the two largest rocks; nine individuals were found in total.

The Cabbage Tree bay, location contained the largest population of A. spinifrons out of the four. 15 individuals were found. It was a Channel (Fig 1.1) that became completely submerged at High Tide, the channel opened out facing the ocean and into the sheltered side of a small cove. The area that contained A. spinifrons had a large number of rocks half submerged in 150mm of water, the population mainly cantered around the largest rocks in the middle of the channel with juveniles spread out around the smaller rocks. The area was bare of any macro algae. Animals occupying the same rocks as A. spinifrons were Palaemon affinis and Diplocrepis puniceus. The substrate around the population was smooth pebbles and solid rock, directly beneath the rock finer grade of pebbles was found, this contained many Opinonereis fasciatus.

The Matapouri Bay Population was the smallest of the four with only five individuals being found. It consisted of four large rocks (Fig 1.2) in 100mm of water. The area was exposed to wave action, large numbers of Actina tenbrosa were found near A. spinifrons on the sheltered side of the rock. Sharing this set of rocks were Notomithrax ursus, Scutus breviculus, Evinchinus chloroticus and diplocrepis puniceus.

The Pebble Bay location differed from the other locations as it was fed continuously by the sea even at MLWS. Water depth was 200mm the eleven individuals that were found were more separated than in the other locations occupying eight different rocks (fig 1.3). Corraline algae was present on the rock surface, and Animals present were Opinonereris fasciatus, Diplocrepis puniceus, Palaemon affinis, Acanthoclinus quadridactylus, Petrolisthes elongatus and Ischnochiton maorianus.

Discussion Alope spinifrons, on the Matapouri Bay to Woolleys' Bay coast, preferred a sheltered rock beach; the reason for this may be because of security when they hide beneath mobile rocks.

Overall water chemistry matched the Ocean, A. spinifrons was never found in a true rock pool that would have swinging temperature, pollution, and reduced oxygen content. This is significant for keeping A. spinifrons in captivity. Water quality must be high to avoid stress.

A. spinifrons was never found in or around Macro Algae, this may be due to the terrain, Suitable hiding places on this particular coast may have been inhospitable for macro algae. Animals that occupy Macro Algae also may compete with A. spinifrons.

In the areas with mobile rocks, only the rocks with clean or solid substrate had A. spinifrons underneath, If the rock sunk to far beneath the substrate surface of if organic matter was found the rock would be absent of A. spinifrons.

In areas with a large population of A. spinifrons , Palaemon affinis was only present if the individual was more than 15mm in length, this either indicated a niche overlap or predation from A. spinifrons.

Water depth ranged from 100mm to 200mm it appeared that A. spinifrons needed quality water but not quantity, at Moturiki Island at Mount Maunganui Beach A. spinifrons was observed out of the water clinging to rock in a crevice alongside Hemigrapsus edwardsi being submerged only by swash.

When disturbed A. spinifrons would remain still even if the rock it was on was completely out of the water, until suddenly it would scuttle across and leap into the water. It would then seek out the largest rock nearby for it to hide. Reasons for A. spinifrons hiding, would be to avoid day time predators, the species is nocturnal and prefers to hunt at high tide((Miller, Batt 1973) . Feeding during the day is purely opportunistic, any creature small enough and unfortunate to come close enough to A. spinifrons is taken