R Stewart

Three recently recorded Ostreopsis spp. (Dinophyceae) in New Zealand: Temporal and regional distribution in the upper North Island from 1995 to 1997

Abstract Three species of epiphytic dino‐flagellates—Ostreopsis siamensis, O. lenticularis, and O. ovata have recently been found on both the east and west coasts of the upper North Island, New Zealand. The morphological differences of all three Ostreopsis spp. have been studied with both light and scanning electron microscopes. Detailed studies of the inner face of the thecal wall of Ostreopsis siamensis revealed two types of trichocyst pores: small, simple pores and large multipore structures. The multipore structures apparently have not been previously reported. Surveys conducted during the period from November 1995 to April 1997 showed that all three Ostreopsis spp. were fairly widespread in northern New Zealand, and all three species were found to occur south of 35°S latitude. Cell concentrations of Ostreopsis spp. in summer were substantially higher than in early spring. There was also a clear regional difference in distribution; cell concentrations of the dominant species, O. siamensis, were greatest in Rarawa and Tokerau on the north‐east coast. Other less abundant epiphytic species recorded during the same period included Prorocentrum lima, P. compressum, and Coolia monotis. These species were generally more sporadic in distribution than Ostreopsis spp.

Stock enhancement of rock lobsters (Jasus edwardsii) : timing of predation on naïve juvenile lobsters immediately after release

Abstract The success of enhancement programmes hinges on the survival of released animals. One factor greatly influencing short‐term survival of reseeded lobsters is the timing and intensity of predation relative to the time of release. The activity and abundance of predators varies over daily, seasonal, and annual scales and knowing the best time to release juveniles will minimise mortality. We used chronographic tethering devices and remote video equipment at 10 sites near Wellington, New Zealand and Hobart, Tasmania, Australia, to assess the relative timing and intensity of predation for released lobsters. Our studies showed that predation was greatest within the first 2 h after release (χ 2 = 60.425, d.f. = 9, P < 0.001) suggesting that the disturbance associated with the release itself may draw the unwanted attention of predators. Relative predation rates also peaked on each of the following two mornings, possibly because of the emergence of daytime predators. The video footage obtained at the Tasmanian sites revealed that most predation was by fish (46%), but surprisingly, cannibalism comprised 16% of predation events. The limitations of tethering as a method are discussed in numerous reviews but proved useful as a relative measure for these highly mobile and cryptic animals. Further consideration needs to be given to methods of release that minimise mortality of recently seeded lobsters.

Anti-Predator Behavior of Captive-Reared and Wild Juvenile Spiny Lobster (Jasus edwardsii)

Early juvenile lobsters reared in captivity may loose anti-predator behaviors displayed by their wild counterparts. To test this hypothesis in juvenile spiny lobsters (Jasus edwardsii), we conducted a series of experiments in which recently settled pueruli were reared in captivity under differing levels of predation risk. After one year in captivity, these lobsters were exposed to a predator in a tank or released into the wild to assess their ability to recognize and respond to predation. We found that lobsters raised without predators significantly reduced their movement activity outside shelters when subsequently introduced to a predator compared with juveniles raised with predators (F1,45 = 4.33, p < 0.05). This apparent over-compensation may be necessary for lobsters to learn the appropriate anti-predator response. Lobsters raised without predators and released into the wild displayed the same types of behaviors as resident wild lobsters. Released lobsters spent more time defending and fighting amongst themselves than the wild lobsters (G = 13.006 > χ2 0.05,2 = 9.488), but they displayed the appropriate anti-predator responses when approached or attacked by a predator. Our results show that juvenile spiny lobsters habituate to the absence of a predator when reared in captivity for long periods, but display an innate ability to recognize and effectively respond to predators when encountered in a hatchery environment or in the wild.

Immunofluorescent detection of a PSP‐producing dinoflagellate,Alexandrium minutum, from Bay of Plenty, New Zealand

Abstract In this study the cross‐reactivity of an antibody raised against cell surface antigens of Alexandrium minutum Halim, a dinoflagellate isolated from the Bay of Plenty, New Zealand, during the 1993 toxic shellfish outbreaks, was tested on other strains of the same species isolated from a variety of locations, as well as a wide range of unrelated phytoplankton using an indirect immunofluorescence staining technique. The antibody showed positive reactions to all four isolates of A. minutum from different localities in New Zealand and one from South Australia. The antibody also showed a positive, but weaker, reaction to A. ostenfeldii (two isolates) from New Zealand but no reaction with A. lusitanicum, a species which is morphologically similar to A. minutum. No cross‐reactivity was observed with 51 species or strains from 10 different algal classes tested. The antibody bound to cells of A. minutum preserved with either 2.5% glutaraldehyde or 3.5% formaldehyde. Recognition of cells in stationary growt...

Spiny lobster population enhancement: moderation of emergence behaviour of juvenile Jasus edwardsii reared in captivity

Abstract Lobster stock enhancement efforts have generally met with limited success owing, in part, to low survival of reseeded juveniles caused by poor development of anti‐predator behaviour. We found that recently‐settled juvenile lobsters reared in captivity for 1 year exhibit significantly higher levels of daytime activity than their like‐sized wild counterparts and that this daytime activity could be reduced by 50% by either rearing the lobsters with a predator or by feeding them at night. In combination, predator presence and night‐time feeding further reduced daytime emergence to low levels. However, a field experiment in which we observed the behaviour and emergence times of captive‐reared lobsters immediately after release on reefs where predators were abundant, showed that regardless of rearing conditions and associated changes in behaviour, lobsters assess the risk of predation and quickly assume nocturnal emergence and activity patterns. This plasticity in behaviour may enable juveniles to maximise foraging range and duration in response to predation pressure.

Conservation of unique patterns of body markings at ecdysis enables identification of individual spiny lobster, Jasus edwardsii

Abstract Southern temperate rock lobsters (Jasus edwardsii) develop complex body markings and spines that vary uniquely among individuals. These markings are retained after moulting allowing individuals to be recognised without capture or handling in the field. This enables the impact of capture, handling, and tagging procedures on subsequent movements to be more confidently evaluated. Recognition of individuals by natural markings allows post‐moult lobsters that were externally tagged and held in large communal tanks to be correctly retagged. Distinctive markings on the pedate processes and on the epistoma, as well as the number and placement of small spines on the antennular plate are particularly useful for recognising individuals. It is highly likely that the other Jasus species and the brightly patterned and coloured Panulirus species have similar body markings and spine patterns that would aid recognition of individuals.

Mesophotic Ecklonia radiata (Laminariales) at Rangitāhua, Kermadec Islands, New Zealand

Abstract: A population of the kelp Ecklonia radiata (Laminariales) has been found in mesophotic conditions at c. 72–80-m depth on the shelf surrounding Macauley Island, Rangitāhua, Kermadec Islands (30°13.3′S, 178°23.8′W), in northern New Zealand, c. 900 km northeast of New Zealand on the western margin of the South Pacific Subtropical Gyre. This species was identified morphologically and with sequence data. This is the first confirmed report of this kelp species growing at the Kermadec Islands, in a location four degrees farther north than previously recorded in the New Zealand archipelago. This discovery joins recent global reports of populations of Laminariales in deep tropical and subtropical habitats, postulated to serve as refugia and potential hot spots of diversity and productivity.