WORLD WIDE DISTRIBUTION?

Transcription

1 311a ECOLOGY AMD BEHAVIOUR- Distribution WORLD WIDE DISTRIBUTION? The vast majority of the fish found in the Reserve are temperate representatives of widely distributed tropical and subtropical families 7 obut some belong to families more restricted in their distribution. The Aplodactylidae, Latridae, Cheilodactylidae and Chironemidae are southern temperate families. Members of the family Parapercidae are largely antarctic and subantarctic fishes. Of all the families represented in the Reserve, only one, the Blenniidae, is present in tropical, temperate and polar regions. Most families are typically shallow inshore groups. There are three basically deep water families represented in the Reserve? Trachichthydae (roughies), Berycidae (golden snapper) and Pentacerotidae (boarfish). There are nine families of typically open ocean pelagic fishes; Carangidae, Arripidae, Mugilidae (mullets), Engraulidae (anchovies), Clupeidae (herrings and pilchards), Scombridae (mackerel) Gempylidae, Isuridae (mackerel sharks) and Molidae (sunfish). At the species level, only the sunfish (Mota mot a) has a worldwide distribution. A few others also have wide distribution ranges. The mackerel (Scomber australasicus) is found between the latitudes of 45 N and 45 S. Both the snoek (Thrysites atun) and the mako shark (Isurus oxyrhinchus) range throughout the southern hemisphere. Several species occur throughout the Indo-Pacific region (e.g. the john dory, Zeus faber r and the red gurnard, Chelodonichthys kurnu) This region includes New Zealand, Australia, the Malay Peninsula, China and Japan. Most species are restricted to Australasian waters. That is, they occur around New Zealand, Australia and several of the surrounding island groups - the Chathams, Kermadecs, Lord Howe Island, Campbell Islands and the Auckland Islands. Several species are endemic to New Zealand, meaning that they are only found in New Zealand waters. These include all the tripterygiids,

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3 313'" certain times of the year. For example,the kingfish (Seriola grandis), kahawai (Arripis trutta) and the sharks are more common over the summer. In other species such as the koheru (Decapterus koheru) and trevally (Caranx georgianus), only the juveniles are commonly found in coastal waters, the adults preferring the open sea. Some of the reef associated fish range widely over the whole reef, usually encompassing several different habitat types (e.g. john dory, Zeus faber, and the rays). The small to moderate-sized fish generally occur in areas where there is plenty of food and shelter from predators or at preferred breeding areas. The different requirements of each species results in certain fish being found in particular habitat types. Thus, the herbivorous fish occur most commonly in broken rock habitats where there is heavy algal growth and the reef associated planktivores (e.g. sweep Soorpis aequipinnis and butterfly perch Caesioperca lepidoptera) are most abundant where there is strong water movement bringing a continuous supply of food. Such small scale patterns of distribution and abundance can be accounted for by juvenile recruitment patternsthe chances of survival after settlement or movements between habitats. In some species the the distribution and abundance patterns of juvenile settlement explains the patterns observed for the adult populations. For example, adult leatherjackets {Parika scaber) are most common in areas where there are high levels of juvenile settlement. In other species similar numbers of juveniles may settle into several different habitat types; however, subsequent juvenile survival might differ. Juveniles of the mottled blenny (Forsterygion varium) settle in similar numbers into all habitat types y but few survive to maturity on the rock flat, turf flat and sponge garden habitats. Lack of shelter and high predator densities in these areas are the most likely causes of high mortality rates. However, The availability of food and the presence of competing species may also influence the distribution patterns of many species. In several species the distribution of the juveniles differs from that of the adults. For example, juvenile red moki (Cheilodactylus spectabilis) are found only in shallow waters (O-lm). As the fish grow they tend to move to deeper water habitats. The reverse situation occurs with snapper (Chrysophrys auratus) and blue cod (Parapercis colias) where juveniles are found in deep waters and tend to move into shallow areas as they grow. Gradual shifts in habitat with age also occur in paketi

4 314a (Pseudolabrus celidotus). These fish recruit exclusively into algal plants and as they become less dependent on shelter, and their food preferences they move to the more open broken rock and rock flat habitats. <eti (Pseudolabrus celidotus) habitats to spawn during the turf flat habitats over summer, but are virtually absent from the in winter. This indicates their movements are of a - on and off the reef. As far as reef fish are concerned nothing been observed on the scale of the classical migrations, where fish travel thousands of miles along a certain route each year, to jrounds. Typical examples are the hatch in shallow streams. The young spend their life in freshwater, grow to maturity in the sea and then return to the of their birth to spawn. The bluefin tuna migrate about the same ;, to the waters of Nova Scotia, Prince Edwarc they feed on large schools of herrings, and squid. If the prey departs their, customary haunts the bluefin follow. While many fish are equally abundant in the shallow and deep of the Reserve (0-20m) (e.g. paketi, Pseudolabrus celidotus, the Y, Forsterygion varium, and the spectacled blenny, Gilloblennius tripennis) others have a more definite depth distribution. as fish, such as the black angeifish (Parma alboscapularis), (Girella tricuspidata), and the silver drummer {typhosus 0, are most commonly found in shallow waters to depth of 5m. scarlet wrasse (Pseudolabrus miles), pigfish (Bodianus oxycephalus), golden snapper (Trachichthodes affinis), lizardfish (Synodus sp.) and the boarfish (Paristiopterus labiosus and Zanclistius elevatus) are sweep (Scorpis aequipinnis) and blue rnaomao (Scorpis violaceus) usually C.hypsilepis) are found below them, and even deeper still are the of butterfly perch (Caesioperca lepidoptera) pink rnaomao

5 315a (Caprodon longimanus) and splendid perch (Callanthias allporti). the pelagic schooling fish are usually found in surface and midwaters. Feeding The fish of the Reserve can be organised into groups according to their foraging behaviour and the food they eat. HERBIVORES: Marblefish (Aplodactylus meandratus), black angelfish (Parma alboscapularis), parore (Girella tricuspidata), silver drummer (Kyphosus sydneyanus) and butterfish (Odax pullus) are exclusively herbivorous. The first two species graze on the small red, green and brown algae, cropping the plants close to the substratum* The latter two are considered, to be plant browsers, selectively feeding on parts of brown algae plants. The reproductive branches of the CarpophyIlum plants appear to be the preferred food when present. Parore are partially grazing and partially browsing in habit. They are often observed grazing the small red algae off the rocks, or the epiphytic red algae off the large brown algae. About half the diet consists of parts of large brown algal plants. These fish usually have a small mouth which works with a crablike action. The small, close-set, incisor-like teeth form and effective cutting and rasping surface. Some species are partially herbivorous. The piper (Reporhampus ihi), for example, appear to be herbivorous in harbour areas, but they eat small planktonic crustacea in coastal areas. (a) Bottom fossickers - these fish forage over the substratum taking invertebrates from amongst the rocks, encrusting growth and algae. The wrasses are typical of this group, taking small sedentary invertebrates such as bivalves, and mobile invertebrates such as chitons, limpets and other gastropods, crabs, hermit crabs, brittle stars and amphipods. These fish are characterised by small protrusible mouths and prominent forwardjutting canine teeth which are effective in removing animals from the substratum Strong pharyngeal teeth for crushing hard shelled prey are also associated. Those fish feeding predominantly on the larger hard shelled invertebrates, including the sea urchins, usually have canine-like teeth in the front of the jaw, for wrenching prey from the substratum, and

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7 317a koheru), trevally (Caranx georgianus), horse mackerel (Trachurus novaezelandiae), spendid perch (Callanthias allporti), pink maomao (Caprodon longimanus), two-spot demoiselle (Chromis dispilus), single-spot demoiselle (C.hypsilepis), the pilchards (Sardinops neopilohardus), anchovies (Engraulis australis) -and the oblique-swimming biennies (Forsteygion sp. C) occupy this role in the Reserve- At night the slender roughies (Eoplostethus. elongatus) and bigeyes (Pempheris adspersa) take over. Rather than gulping large masses of water these fish pick individual plankters out of the water, taking them with a snapping action, (f) Parasite cleaning - fish obtaining their food by picking parasites from the body, mouth and gills of other fish are known as cleaners. Cleanerfish are usually small and have prominent snouts and tweezer-like front teeth. These fish are often actively sought after by parasite infested fish. Bright, distinctive colour patterns and the conspicuous displays performed by some species aid in advertising the presence of the cleanerfish to the hosts. Paketi (Pseudolabrus celidotus) and Sandager! s wrasse (Coris sandageri) are the only members of this group found in the Reserve. Only the juveniles of these species may act as cleaners whereas other species (e.g. crimson cleanerfish, Suezichthys sp., act as cleaners throughout their lives. All these species are part-time or facultative cleaners, which although often observed feeding off other fish, they also spend a great deal of their time fossicking on the bottom. Cleaning activity is not commonly observed in the Reserve. However, in the warmer waters around the Poor Knights Islands the fish tend to be more heavily infested with parasites and cleaning behaviour is frequently observed. Many species receive attention from cleanerfish, especially goatfish (Upeneichthys porosus), two-spot demoiselles (Chromis dispilus), red moki (Cheilodactylus spectabilis) and trevally (Caranx georgianus). PISCIVORES (a) Midwater hunting - fish such as the john dory (Zeus faber), kingfish (Seriola grandis) and kahawai (Arripis trutta) rove over the entire reef. They are largely piscivorous in habit, feeding on smaller pelagic and reef dwelling fish. In these fish a large terminal mouth facilitates the swallowing of the fish whole. The teeth may be strongly developed, for catching and holding prey, or rudimentary. John dory rely on slowly stalking

8 318a their prey and then suddenly extending the large mouth to engulf it. Other midwater hunters depend mainly on their speed and the surprise of sudden attack to capture their prey. (b) General predation and scavenging - the sharks belong to this category in which fish continually rove in midwater and over the bottom taking live or dead prey indiscriminantly. The rich invertebrate fauna living amongst the encrusting material on the rocky reef provides by far the most important food source for the reef fishes. This includes the small mobile crustacea such as amphipods, isopods, crabs, hermit crabs, small gastropods, polychaetes and brittlestars. Of these amphipods have the highest food utilization, especially by juveniles fish. The larger sedentary invertebrates, the large gastropods, chitons, sea urchins (echinoids) and brittle stars (ophiuroids), and the sessile bivalves are also heavily exploited. The planktonic crustacea; the copepods, ostracods, and euphausid shrimps, and the larvae of these, the benthic crustacea and other invertebrate groups are an important food source for the plankton feeding fish. Fish eggs and larvae, the doliolids (salps) and larvaceans (e.g. Oikopleura) are taken in large quantities when these are seasonally Algae have a restricted use as a food source. Only five fish species found in the Reserve are exclusively herbivorous. Sponges, ascidians, hydroids and bryozoans are relatively poorly utilized and form an important food source for only one species, the leatherjacket (Parika scaber). The sharp spicules, tough fibrous tissue and toxic chemicals found in the sponges render them unpalatable to most fish. Relatively few fish in the Reserve feed on other fish. However, all species are vulnerable and especially at the egg and larval stage. Behaviour The aspects of fish behaviour associated with feeding, reproduction or survival are considered under their respective headings. Here, the activity patterns, modes of social organisation and the associations fish form with other animals and fishes are discussed.

9 319a ACTIVITY: Most fish in the Reserve are diurnal, meaning that they are active during the day. At night diurnal fish sleep, usually sheltering among the rocks and seaweed or in crevices. Some rest in the open on the bottom (e.g. goatfish, Upeneichthys porosus), or hover in the water column just above the bottom (e.g. sweep, Scorpis aequipinnis). Some species are crepuscular, being most active at dawn and/or dusk (e.g. redbanded perch, Ellerkeldia huntii; parore, Girella tricuspidata; hiwihiwi, Chironerrrus marmoratus and marblefish, Aplodactylus maandratus). In these fish activity is markedly decreased during the day; however, some feeding and swimming activity, and social interaction may be observed. There are eight noctunal, or night active species found in the Reserve. These are the true cod, the moray eels (Gymnothothorax prasinus), conger eels {Conger wilsoni), scorpionfish.(scorpaena cardinalis), slender roughy (Hoplostethus elongatus) and bigeyes (Pempheris adspersa). These fish rest during the day in rocky shelters, although occasionally they may be seen moving from shelter to shelter or feeding. At night they feed openly on the bottom, or as in the case of the last two species, in midwater. Changes in activity patterns may occur with age within one species. For example juvenile bigeyes (Pempheris adspersa) are active during the day whereas the adults are nocturnal. SOCIAL ORGANISATION: The ways in which fish space themselves with respect to other fish of the same species in their immediate vicinity is often characteristic of the species and can be useful in their identification. Fish can be broadly divided into those that live in groups and those that lead a solitary existence. Most midwater or surface swimming fish form large aggregations (e.g. two-spot demoiselles, Chromis dispilus; sweep, Scorpis aequipinnis and pink rnaomao, Caprodon longimanus). The individuals forming each group are usually of similar size; however aggregations of some species (e.g. butterfly perch, Caesioperca lepidoptera) often contain a wide size range or individuals. Mixed species groups also often occur, especially between sweep (Scorpis aequipinnis) and blue rnaomao (S.violaceus).

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11 321a and size. Juvenile paketi (Pseudolabrus oelidotus), for example, tend to be gregarious I As these fish grow the spacing between individuals gradually increases until they become solitary. The females in this species are home ranging while the males defend territories. In some * f species both males and females are territorial (e.g. the mottled blenny, Forsterygion variwn). At very low or high population densities the typical social organisation of a species may break down. The male territorial system described above for paketi is not evident in high population densities; the males become home ranging, like the females, and there is very little aggressive activity. The distribution and abundances of the resources being defended may also affect the social organistion of some species in different areas For example, on the turf flats in the Reserve food is plentiful and relatively evenly distributed for snapper (Chrysophrys auratus) and goatfish (Upeneichthys porosus). In this habitat these fish are usually found in groups. However, in other habitats where food is less abundant or is patchy in distribution the fish are solitary, defending feeding territories from other members of the same species. For many territorial fishes interspecific interactions (i.e. interactions with fish of a different species) make up a considerable proportion of the total number of interactions in which the fish is involvedo These interactions are paricularly noticeable between the mottled blenny (Forsterygion varium) and paketi (Pseudolabrus oelidotus) in the Reserve. The blenny vigorously defends its territory from the larger fish which feeds on similar foods and also will eat the blenny's demersal eggs if it is allowed. Interactions between fish usually take the form of ritualised displays. Low intensity interactions usually consist of fin displays and mouth gaping. The fish involved may face each other or orient side by side, their dorsal and anal fins spread and their mouths open. More aggressive interaction^ often involve quivering, the fish turning about in tight circles and often some form of physical contact such as nipping or jaw locking. These interactions usually occur between individuals at territory borders. Other types of interactions include the chase and flee situation, where one fish swims rapidly toward the other, often nipping it, and chases it away. In these interactions the territory holder is usually successful in driving the intruder away.

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13 323a CAMOUFLAGE AND BEHAVIOUR: Fish may deceptively resemble an object which is of no interest to a predator. For example the colouring and weed-like appendages of the crested weedfish (Cristiceps aurantiacus) blend excellently when the fish is amongst the kelp. These fish are also very secretive and are rarely seen away from their algal habitat. The scorpionfish (Scorpaena cardinalis) is well endowed with appendages, particularly around the the eyes and across the gill covers. This, in combination with their mottled appearance, gives the fish the appearance of the sponges or rock surface on which it rests. If detected these fish also have another means of defence in the form of poisonous spines. Many other bottom dwelling fish are coloured and patterned to match their surrounding environment. Thus species such as the marblefish (Aplodactylus meandratus), the mottled blenny (Forsterygion varium) and the chequered blenny (Eelcogramma sp.a) are nearly invisible against their background when resting. Many of these fish 1 freeze 1, remaining perfectly motionless when a predator approaches. Others will immediately dash to nearby shelter. Some fish change their colour patterns when they move from one set of surroundings to another. The parore (Girella tricuspidata) and pink rnaomao (Caprodon longimccnus) change their colours for protective purposes at night, or in the latter case when resting on the substratum during the day. A habit of covering the body with sand acts as a further, defence for many species. The spotted stargazer (Genyagnus monopterygius) buries itself in the sand with little more than their eyes and mouth protruding. Some rays (e.g the stingrays and eagle ray) also throw sand up over their bodies when resting on the bottom. Certain species may imitate, or mimic another species of fish in appearance and behaviour. This strategy may be used by the mimic species to gain some particular advantage, particularly those related to feeding as seen for the mimic blenny (Plagiotremus tapeinosoma) (see page 322 ), or to obtain a 'safe pass' from its enemies. For example, the small virtually defenceless saddleback leatherjacket (Paraluteres prionurus) from Australia mimics the colour pattern of another highly poisonous leatherjacket species and is avoided by most predators. Mimicry among marine fish appears to be a general and widespread phenomenon. The known examples suggest that there may be varying degress of resemblance. In some cases the mimic-model relationship may be loose

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15 325a WEAPONS AND ARMOUR: If a fish is detected by a predator, despite attempts to remain inconspicuous, it may have other methods of defence in the form of weapons and armour. Body spines may be used as a deterrant to the attacker, a weapon which can inflict a painful wound or as a shield to make swallowing difficult. Many teleosts have strong spines in their dorsal fins. Sensing danger a fish can raise these spines as a warning to the predator. This also enlargens the fish's external appearance and may help to deter the would be attacker. If a predator should attack the spines would simply fold along the body. Some species, however, are able to lock their spines in an erect position (e.g. the leatherjacket., Parika scaber) which would create a painful obstruction if the predator should attempt to swallow the fish. The porcupine fish (Allomycterus whitleyi) inflates its body by swallowing water when threatened. Although this renders the fish virtually immobile it increases the body size by almost three times, and the spines which cover the body project stifly at right angles to the body, making this fish very hard to swallow. The seahorses and pipefish (Syngnathidae) are encased in an armour of rigid bony plates which gives the fish an immunity from the sharp teeth of many potential predators. Scorpionfish (e.g. Scorpaena cardinalis) possess several poisonous dorsal fin spines. When provoked the fish usually flare their dorsal fins, displaying the spines to the attacker. Stingrays usually flee from predators, but when cornered they may strike with their serrated, dagger-like spine which is situated at the base of the tail. The effect of the poison from these fish on humans varies depending on the species of fish and the depth and severity of the wound. Certain tropical leatherjackets (Monacanthidae) and pufferfish (Lagocephalidae) possess a powerful poison in the skin, intestines, gonads and flesh. These fish are usually brightly coloured, signifying them as dangerous to predators. The stunning effects of an electric current is another means of; defence (see page ). The most vulnerable stage in the life cycle of a fish is the egg and larval stage. These are generally small and have very few defences. The eggs may be encased in a tough leathery capsule as in many of the oviparous sharks and rays. Nest guarding by parent fish and the habit of laying demersal eggs in relatively inacessable sites increases the chances of survival to the hatching stage for many fish. The pelagic

16 326a eggs of the midwater spawning fish are almost transparent and are often spawned in areas where predation pressure is likely to be low. For example, female paketi {Pseudolabrus celidotus) appear to prefer to spawn in deeper waters where the densities of planktivorous fish are relatively low. Pelagic larvae are also transparent. Some.such as the sunfish (Mola mola) develop protective spines at this stage. Fish eggs and larvae are usually eaten in large numbers, mainly by the plankton feeding fish. It has been estimated that only about one in every million eggs spawned survives to reach maturity and breed itself. LIFE HISTORY AMD. REPRODUCTION Age and growth GENERAL FEATURES: Unlike other vertebrates fish continue to grow throughout their lives (indeterminant growth). They all follow the same general pattern - initially growth is rapid until the fish reaches the size at which it becomes sexually mature, then growth continues but at a decreasing rate. So far only one exception has been found among the fish of the Reserve. The leatherjacket (Parika scaber) exhibits a determinate growth pattern, the fish growing to certain size after which there is no evident increase in length. Within a species the growth rate of an individual fish varies, not only with age as described above but also with location and season. These variations are usually ultimately associated with temperature and/or food. Fish in the warmer parts of their range usually grow faster than individuals of the same species in colder regions. For example, the mottled blenny (Forsterygion varium) grows to reach 80mm in length in less than one year in the Reserve, but they take three to four years to reach this size in southern parts of the South Island. The quality and quantity of food available to each fish also affects growth rates and probably explains differences in growth between local populations and between males and females of the same species. Male yellow-eyed mullet (Aldrichetta forsteri), for example, tend to spend longer periods of time