Mass spawning by the sea urchin Evechinus chloroticus (Echinodermata: Echinoidea) in a New Zealand fiord

A mass synchronous spawning of the sea urchin Evechinus chloroticus (Valenciennes) was observed in situ in Doubtful Sound, a large New Zealand fiord. Spawning occurred between 17:30 hrs and 18:30 hrs on 27 January 1994 and coincided with a full moon, spring tides and a period of decreasing sea temperatures. During spawning, the sea urchins formed a dense spawning aggregation of both sexes, with >90% of the urchins observed spawning at the time. Spawned gametes clouded the water column, and some were eaten by small labrid fish species. The spawning, which may have been as widespread as 40 km, marked a 42 to 50% decrease in gonad indices and resulted in a widespread, dense cohort of  E. chloroticus larvae within the fiord. Received: 25 September 1997 / Accepted: 6 March 1998     

Movements and food habits of striped bass (Morone saxatilis) in Delaware Bay (USA) salt marshes: comparison of a restored and a reference marsh

 There has been much recent interest in restoration of salt-marsh habitats to their natural structure and function. However, the criteria for success of such restorations are not well-defined. As part of a larger program to evaluate the restoration of a former salt-hay farm bordering Delaware Bay, New Jersey, USA, we monitored the response of a large predator, the striped bass Morone saxatilis, to the restoration. During June to October 1998 we compared tidal and diel movements and food habits of juvenile and adult striped bass (n = 82, 212 to 670 mm fork length) between a restored marsh and an adjacent reference marsh with similar physical characteristics (depth, salinity, temperature). Striped bass movements at both sites were characterized by ultrasonic tracking with small, surgically implanted tags (21 d rated battery-life). Striped bass (n = 23, 421 to 610 mm fork length) were tagged and released near the main creek mouths at both the restored (n = 14) and reference (n = 9) marshes. At both sites, striped bass tended to move up the main creek during ebb tide. At the restored site, ebb tide upstream-movements ranged from 0.1 to 3.5 km from the main creek mouth (mean = 1.2 km). During the upstream movement, the fish typically stopped every 200 to 300 m (presumably to feed) for 1 to 2 h. At the reference site, few of the tagged fish moved farther than 100 to 200 m upstream from the main channel mouth at ebb tide, perhaps in response to somewhat lower dissolved oxygen at this site. During flood tide, tagged fish at both sites moved out into Delaware Bay, where they remained within 200 to 500 m of the creek mouth. Striped bass were sampled with gill nets to determine additional aspects of habitat use and food habits. Striped bass in both marshes were much more abundant at creek mouths (catch per unit effort, CPUE = 1.17) than in the upper reaches of the creeks (CPUE = 0.13). In the creek mouths, CPUE was greater at the restored site (CPUE = 1.8) than at the reference site (CPUE = 0.5). At both sites, most fish (approx. 80%) were collected on the late ebb or early flood tides, i.e. around low tide, when prey were presumably concentrated at the creek mouths. Stomach contents of bass from both restored and reference marshes (n = 59, 212 to 670 mm fork length) revealed that striped bass were eating mostly blue crab (Callinectes sapidus), grass shrimp (Palaemonetes vulgaris), sand shrimp (Crangon septemspinosa), mummichog (Fundulus heteroclitus), and various unidentifiable fishes (probably anchovies, Anchoa mitchilli, and Atlantic silverside Menidia menidia). In conclusion, the restored marsh supported larger numbers of striped bass than the reference marsh, but there was little difference in the pattern of creek utilization or food habits at either site. Thus, the restored marsh appears to be functioning in a similar manner to the reference marsh for these large predators. Received: 28 June 1999 / Accepted: 1 August 2000     

Does the composition of the demersal fish assemblages in temperate coastal waters change with depth and undergo consistent seasonal changes?

The aim of this study was to determine whether the composition of the demersal fish fauna in coastal marine waters in temperate Australia changes markedly with increasing water depth and distance from the shore and whether the composition of the fish fauna in water depths of 5 to 35 m undergoes cyclic, seasonal changes. Samples of demersal fishes were therefore collected by trawling over the predominantly sandy substrate at nine sites located in water depths of 5 to 15 m or 20 to 35 m and within 20 km of the shore in four regions along ∼200 km on the lower west coast of Australia. The sampling regime involved trawling for fishes at each site at night in seven consecutive seasons between the summer of 1990/1991 and winter of 1992. A total of 72 435 fishes, representing 77 families, 143 genera and 172 species was caught. The compositions of the fish faunas in offshore waters with depths of 5 to 35 m were shown to differ markedly from those previously recorded for nearshore marine waters in the same regions. However, as some species, such as Sillago burrus, S. vittata, S. bassensis and Rhabdosargus sarba, increase in size, they move out from their nursery areas in nearshore waters into deeper and more offshore waters, where spawning occurs. Ordination showed that, in each of the four regions, the composition of the fish fauna in depths of 5 to 15 m differs from that in depths of 20 to 35 m. This difference is attributable to the fact that some species, such as  S. burrus, S. vittata and Upeneichthys lineatus, are far more abundant in depths of 5 to 15 m, whereas other species, such as S. robusta, U. stotti and Lepidotrigla modesta, occur predominantly in depths of 20 to 35 m. However, the samples collected from the single site that was inshore but in deeper water demonstrate that the composition of the fish fauna is influenced by distance from shore as well as by water depth. The compositions of the fish faunas differed with latitude, largely due to the fact that some subtropical species, such as Polyspina piosae, S. burrus and  S. robusta, did not extend down into the more southern regions. Ordination also showed that the composition of the fish faunas at all but one of the nine sites underwent pronounced and consistent cyclic, seasonal changes. This seasonal cyclicity at the different sites was attributable to sequential patterns of immigrations and emigrations by a number of fish species during the course of the year. These seasonal migrations involved, inter alia (1) movements of certain species from their nursery areas into these deeper waters, e.g.  S. bassensis and Scobinichthys granulatus; (2) migrations into and off the sandy areas of the inner continental shelf, e.g. Arnoglossus muelleri; (3) migrations to spawning areas, e.g. Sillago robusta; and (4) movements into areas where detached macrophytes accumulate in winter, e.g. Cnidoglanis macrocephalus and Apogon rueppellii. Received: 21 August 1998 / Accepted: 9 February 1999     

Tracking adult North Atlantic bluefin tuna (Thunnus thynnus) in the northwestern Atlantic using ultrasonic telemetry

Ultrasonic, depth-sensitive transmitters were used to track the horizontal and vertical movements, for up to 48 h, of 11 adult (136 to 340 kg estimated body mass) North Atlantic bluefin tuna (Thunnus thynnus Linnaeus). Fish were tracked in October 1995, September and October 1996, and August and September 1997 in the Gulf of Maine, northwestern Atlantic. The objective was to document the behavior of these fish and their schools in order to provide the spatial, temporal, and environmental information required for direct (i.e. fishery-independent) assessment of adult bluefin tuna abundance using aerial surveys. Transmitters were attached to free-swimming fish using a harpoon attachment technique, and all fish remained within the Gulf of Maine while being followed. Most of the bluefin tuna tagged on Stellwagen Bank or in Cape Cod Bay (and followed for at least 30 h) held a predominately easterly course with net horizontal displacements of up to 76 km d⁻¹. Mean (±SD) swimming depth for all fish was 14 ± 4.7 m and maximum depth for individuals ranged from 22 to 215 m. All but one fish made their deepest excursions, often single descents, at dawn and dusk. In general, adult bluefin tuna spent <8% of their time at the surface (0 to 1 m), <19% in the top 4 m, but >90% in the uppermost 30 m. Mean (±SD) speed over ground was 5.9 km h⁻¹, but for brief periods surpassed 20 to 31 km h⁻¹. Sea surface temperatures during tracking were 11.5 to 22.0 °C, and minimum temperatures encountered by the fish ranged from 6.0 to 9.0 °C. Tagged bluefin tuna and their schools frequented ocean fronts marked by mixed vertebrate feeding assemblages, which included sea birds, baleen whales, basking sharks, and other bluefin schools. Received: 19 July 1999 / Accepted: 25 March 2000     

Primary cell-culture of the digestive gland of the marine mussel Mytilus edulis: a time-course study of antioxidant- and biotransformation-enzyme activity and ultrastructural changes

The extent to which the American lobster, Homarus americanus (H. Milne-Edwards), utilizes estuarine habitats is poorly understood. From 1989 to 1991 we examined lobster movements in and around the Great Bay estuary, New Hampshire using tag/recapture and ultrasonic telemetry. A total of 1212 lobsters were tagged and recaptured at sites ranging from the middle of Great Bay, 23.0 km from the coast, to Isles of Shoals, 11.2 km offshore. Twenty-six lobsters equipped with ultrasonic transmitters were tracked for periods ranging from 2 weeks to >1 year. Most lobsters moved <5 km toward the coast, with those furthest inland moving the greatest distance. Lobsters with transmitters moved in a sporadic fashion, with residency in one area for 2 to 4 weeks alternating with rapid movement to a new location (mean velocity = 0.3 km d⁻¹, 1.8 km d⁻¹ max.). Site of release influenced distance moved, but there was no significant relationship between lobster size and distance traveled, days at large, or rate of movement. Most movement into the estuary occurred in the spring, while during the remainder of the year there was a strong tendency to move downriver, toward the coast. These seasonal migrations of estuarine lobsters may enhance their growth and survival by enabling them to avoid low salinity events in the spring and fall, and to accelerate their growth in warmer estuarine waters during the summer. Received: 26 January 1996 / Accepted: 22 January 1999     

Reproductive dynamics of endeavour prawns, Metapenaeus endeavouri and M. ensis, in Albatross Bay, Gulf of Carpentaria, Australia

 The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort, and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively. The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for M. endeavouri is August to October and that for M. ensis is September to December. Received: 19 February 1999 / Accepted: 18 June 2000     

Reef coral reproduction in the Abrolhos Reef Complex, Brazil: the endemic genus Mussismilia

The current contribution deals with the reproductive biology of a genus endemic to Brazil –Mussismilia Ortmann, 1890 – including all three species of the genus: M. braziliensis (Verrill, 1868), M. hartti (Verrill, 1868), and M. hispida (Verrill, 1902), which occur sympatrically in the studied area, the Abrolhos Reef Complex, Brazil. Sexuality patterns, modes of reproduction, synchrony and spawning periods are reported, and were determined by histological examination of material. All three species started to develop female and male gametes over different periods in the same breeding season. The three species are probably broadcast spawners, since no embryos or planulae were observed in any species at any given time of the year. Each reproductive cycle lasted approximately 11 months. Oogenesis and spermatogenesis started in different periods, with spermaries appearing in approximately the eighth month of ovary development and lasting about 3 months. Reproductive cycles were annual. Spawning probably occurred in consecutive months in each species. In M. braziliensis, spawning presumably happened between March and the middle of May in 1996 and 1997. Evidence suggested that spawning events of M. hispida took place between the end of April and mid-June. M. hartti may have spawned between September and November. The data presented here suggested that all studied species have at least one exclusive spawning period, asynchronically with the others. A possible exception may be the simultaneous (or close) spawnings of M. braziliensis and M. hispida in May. It is suggested that asynchrony in spawning periods among species may reduce the chance of hybridization, gamete waste and the competition for settlement surfaces. The occurrence of extended spawning periods for each species may also reduce the risks of reproductive failure, due to temporary adverse conditions. Received: 8 December 1998 / Accepted: 15 July 1999     

Plasticity in spawning visits of female damselfish, Stegastes nigricans : effect of distance to mates

Both sexes of the damselfish Stegastes nigricans hold individual territories in which they feed on filamentous algae. At dawn, females visit males' territories to spawn, and the males guard the eggs until hatching. We examined how females' spawning behavior varied according to the distances to their mates. Females usually mated with a single male per morning. The distance to the territory of a mate (0.7–12.8 m) did not affect a female's total spawning time per morning, but affected the number of her spawning visits with that male. Females made many repeated spawning visits when spawning with males at short distances, while they spawned the entire clutch in one visit when spawning with males at long distances. This plasticity in female behavior appears to be related to two costs during the spawning visits: (1) intrusions by other fish to feed on algae in the female's territory during her absence, which may cause the female to return repeatedly to her territory for defense, and (2) attacks on the female by other territorial fish, which increased with the distance to their mates' territories. To minimize the sum of both costs, females should change the number of spawning visits depending on the distance to the males' territories. Received: 30 September 1996 / Accepted after revision: 17 March 1997     

Oxygen transport by the hemocyanin of the protobranch mollusc Solemya reidi

Oxygen transport by the hemocyanin of the protobranch mollusc Solemya reidi Bernard was studied in native hemolymph samples. Clams were collected from two different reducing environments, beneath log booms in Alberni Inlet, British Columbia, Canada, and from the sewage effulent in Santa Monica Bay, California, USA. The hemocyanin concentration in a pooled hemolymph sample (n = 10 individuals) was 33.5 mg ml⁻¹. The mean hemolymph pH of five Alberni clams maintained for 3 wk in mud was 7.96 ± 0.06. No significant variation in hemocyanin oxygen-affinity or cooperativity was found for hemocyanin in whole hemolymph samples from these five individually studied clams. There was a significant difference only at 15 °C in the oxygen affinity of hemocyanin in pooled whole-hemolymph samples from S. reidi collected from Alberni Inlet compared with clams collected from Santa Monica Bay. Little effect of temperature on hemocyanin oxygen-affinity was found for temperatures below 20 °C; above 20 °C, the oxygen affinity was reduced for clams from both sites. Temperature and pH had no apparent affect on hemocyanin cooperativity. Moderate Bohr shifts were found at all temperatures examined. The presence of physiologically relevant concentrations of thiosulphate in hemocyanin samples resulted in a decrease in hemocyanin oxygen-affinity, opposite to the effect on hemocyanin found for the hydrothermal vent crab Byth-ograea thermydron, but thiosulphate had no effect on hemocyanin cooperativity. Received: 2 September 1997 / Accepted: 6 February 1998     

Sex and reproductive aspects in Serranus cabrilla (Osteichthyes: Serranidae): macroscopic and histological approaches

The gonads of Serranus cabrilla (Linnaeus, 1758) from the Canary Islands were studied between September 1992 and July 1993. Macroscopic classification of the maturity stages was compared with histolog ical classification of gonad characteristics, and the effect␣of the classification method on the determination of the spawning season and size at maturity was investigated. Analysis of gonad organization and development confirmed that this species is synchronously hermaphroditic. Ovarian-tissue development is asynchronous, and testicular tissue consists of continuous spermatogonia. Six stages of oogenesis and five of spermatogenesis are described, based on differences in staining and in size and on differences in the nucleus and cytoplasm structure as viewed through a light microscope. Two types of atretic degeneration of eggs are also described. Agreement between macroscopic and histological staging was low, although both methods provided similar results in spawning-season determination and size at maturity. The spawning season of S. cabrilla is from February to July, with a peak in May. Fish size at first maturity (size at which 50% of all fish sampled are in relevant maturity stage) is 152 mm standard length (SL), and size at mass maturity (size at which 95% of all fish sampled are in relevant maturity stage) is 167 mm SL. Received: 21 May 1996 / Accepted: 9 August 1996     

Home range, activity and distribution patterns of a temperate rocky-reef fish, Cheilodactylus fuscus

Red morwong (Cheilodactylus fuscus; Cheilodactylidae: Perciformes), are large temperate rocky reef fish that are patchily distributed in local aggregations of 3 to >100 fish. The home ranges and aggregating behaviour of red morwong were investigated using external tags (n = 114, over 35 mo) and ultrasonic transmitters (n = 9 over 20 d) at coastal and estuarine sites in south-east Australia. Adult red morwong had a mean home range during the day of 1865 m² (SE = 268). Night movement, determined by ultrasonic telemetry, indicated a significantly greater mean home range of 3639 m² (SE = 416). Home range did not differ significantly with size or sex. Fish movements were greatest and aggregation sizes varied most during the non-reproductive mid-summer period. Tagged fish (N = 20) displaced 200 to 900 m returned in 1 to 3 d to the point of capture, often traversing open sand habitat and other aggregations. During the day, fish were commonly found on bouldered habitat. During the night, these site-specific aggregations fragmented as fish dispersed over a variety of substrata, with crepuscular peaks in activity. Therefore, estimates of habitat-specificity and feeding patterns collected only by day may give misleading results. Received: 28 June 1996 / Accepted: 8 July 1998     

Size-dependent reproduction in the Caribbean gorgonian Pseudoplexaura porosa

Reproductive success among clonal taxa is often portrayed as a simple function of clone size, but reproduction in Pseudoplexaura porosa (Houtuyn), a common Caribbean gorgonian, reflects a more complex relationship between size and gamete production. Tagged colonies were sampled at two reefs in the San Blas Islands, Panama during the 1995 spawning season to determine the colony size at first reproduction, size-dependent polyp fecundities, and whole colony gonad production, and to follow the gametogenic cycle. Additional data were obtained during non-spawning months in 1984 and 1985. Of 120 colonies ranging in height from 20 to 250 cm, only colonies taller than 50 cm were reproductive. An average of 4.33 oocytes polyp⁻¹, 560 to 800 μm in diameter, were released during monthly synchronous spawning events from June to September. Oocytes released each month developed from a group of intermediate size oocytes present at the end of the preceding month. Almost all oocytes >560 μm were released during each spawning event. Spermatogenesis was a shorter process than oogenesis. During each spawning month, mature spermaries developed from a group of <125 μm spermaries. Virtually all spermaries >190 μm were released each month, and most of the spermary volume in mature male polyps was generated anew each month of spawning. Among reproductive colonies, polyp fecundity increased with colony height from 50 to 200 cm. Per capita fecundity of >200 cm tall female colonies was lower than for 150 to 200 cm colonies, but whole colony fecundity of large colonies was greater due to the exponential increase in the number of polyps that occurs with increasing colony height. In male colonies, both polyp and colony reproductive output increased with colony height. The large amounts of sperm produced by large male colonies probably contributes to the high rates of in situ fertilization observed in P. porosa. Differences in fecundity as a function of colony size and sex suggest differences in some combination of the cost of reproduction and/or allocation of resources to reproduction. Received: 9 September 1998 / Accepted: 7 June 1999     

Movement patterns of large bigeye tuna (Thunnus obesus) in the open ocean, determined using ultrasonic telemetry

 The horizontal and vertical movements of large bigeye tuna (Thunnus obesus Lowe, 1839; 25 to 50 kg) captured in the south Pacific Ocean (French Polynesia) were determined using pressure-sensitive ultrasonic transmitters. Bigeye tuna swam within the first 100 m below the surface during the night-time and at depths between 400 and 500 m during the daytime. The fish exhibited clear relationships with the sound scattering layer (SSL). They followed its vertical movements at dawn and dusk, and were probably foraging on the organisms of the SSL. Bigeye tuna did, however, make regular rapid upward vertical excursions into the warm surface layer, most probably in order to regulate body temperature and, perhaps, to compensate for an accumulated oxygen debt (i.e. to metabolize lactate). The characteristics of these dives differ from those reported from previous studies on smaller bigeye tuna (∼12 kg) near the main Hawaiian Islands. During the daytime, the large fish in French Polynesia made upward excursions approximately only every 2.5 h, whereas smaller fish in Hawaiian waters made upward excursions approximately every hour. Our data are the first observations on the role of body size in the vertical behavior of bigeye tuna. Received: 9 September 1998 / Accepted: 25 November 1999     

Predation on Euphausia pacifica by demersal fishes: predation impact and influence of physical variability

The importance of Euphausia pacifica Hansen to the demersal fish community off Sendai Bay, northern Japan, was studied based on a total of 256 trawl samples collected during May, October and November, from 1989 to 1992. The samples were classified into 16 assemblages according to year, month and depth. The importance of E. pacifica to the total diet of each of the assemblages was measured using an index considering both fish diet and species composition. A total of 24 fish species out of 87 were found to ingest E. pacifica. Of these, Gadus macrocephaus and Theragra chalcogramma had the highest predation impact due to their dominance in the fish assemblages and the high proportion of E. pacifica in their diets. The contribution of E. pacifica to the total diet of the fish assemblage was highest in the shallow (≤300 m) regions during May, accounting for an average of 38.5% for the 4 years. However, during May 1990, when the warm Kuroshio Extension prevailed, the contribution was higher in the deep (>300 m; 22.6%) region, reflecting active and/or passive movements of E. pacifica. The average predation impact was maximal in the May/shallow assemblage (mean ± SE; 4.6 ± 1.4 kg wet wt km² d⁻¹) and was minimal in the November/shallow assemblage (0.4 ± 0.3). Annual estimates of consumption by demersal fish fishes ranged from 43 to 128 metric tons, representing 15 to 64% of the annual commercial catch of E. pacifica by local fisheries. It is therefore suggested that the fisheries on E. pacifica have the potential to considerably impact the demersal fish assemblages. Received: 3 December 1997 / Accepted: 10 June 1998     

Reproductive biology and ecology of a deep-demersal fish, alfonsino Beryx splendens, over the seamounts off New Caledonia

The reproductive biology of the alfonsino Beryx splendens was studied by histological examinations, gonadosomatic index and macroscopic scales of maturation of a large sample of gonads. Alfonsino is a gonochoric species. The size-frequency distribution of the sex ratio was bimodal and considered to be due to size dimorphism. In New Caledonia, the breeding period of this species occurs during the southern summer, with a peak in December to January. The spawning stage is attained at a minimum fork length of 28 cm for females and 33 cm for males. The size at which 50% of the population attain sexual maturity (FL₅₀) is 33.2 cm for females and 34.5 cm for males. Maximum potential fecundity is estimated to lie between 270 000 to 675 000 eggs for fish between 34 and 40 cm in fork length. It was possible to differentiate vegetative zones, in which juvenile alfonsino grow until they reach maturity, from reproductive zones (fishing grounds) which are inhabited by mature individuals. The larvae and juveniles could be carried from the reproductive zone to the vegetative zone by currents in an oceanic eddy system. Received: 26 April 1996 / Accepted: 20 September 1996     

The fish fauna of a seasonally closed Australian estuary. Is the prevalence of estuarine-spawning species high?

The fish at sites located throughout the large, seasonally closed Wilson Inlet, on the southern coast of Western Australia, were sampled bimonthly between September 1987 and April 1989. Seine nets were used to sample nearshore shallow waters, while gill nets were employed in slightly more offshore and deeper waters. Twenty species were recorded in the shallows, of which the three species of atherinid and the three species of goby comprised >97% of the total catch. In terms of number of individuals, the 27 species recorded in gill nets in the deeper waters were dominated by Cnidoglanis macrocephalus and Platycephalus speculator, and to a lesser extent Engraulis australis, Aldrichetta forsteri, Sillaginodes punctata and Arripis georgianus. Fifty-five percent of the species recorded in the nearshore shallow waters and 18% of those in offshore deeper waters spawn within Wilson Inlet; these species contributed 98.5 and 63.0%, respectively, to the total catches in those waters. Classification and ordination showed that the composition of the fauna in the shallows was similar at all sites throughout the large basin and did not change conspicuously with season. However, the composition of catches taken in offshore waters differed between the lower part of the basin and the middle and upper regions of the basin, which in turn differed from those in the saline reaches of a tributary river. The four diagnostic species of the lower estuary were all marine species, while the three diagnostic species in the river included a marine species (Mugil cephalus) that often penetrates far upstream in other systems, and a species which was confined to the rivers (Acanthopagrus butcheri). The composition of the fish fauna in the offshore waters of the lower estuary between the middle of spring and middle of autumn was different in 1987/1988 (when the estuary mouth was open for only the first two months of that period) from that in 1988/1989 (when the mouth was open for the whole of that period). This difference is related to the greater number of marine species that were retained in the first of these years, when the estuary was open to the ocean for only a short period. The greater retention of marine species in 1987/1988 than in 1988/1989 probably reflects a far lower level of freshwater flusing and/or a less marked decline in salinity.     

Reproduction and growth of Isostichopus fuscus (Echinodermata: Holothuroidea) in the southern Gulf of California, México

The reproduction and growth of Isostichopus fuscus (Ludwig, 1875) at Isla Espíritu Santo, Baja California Sur, México from July 1992 to September 1993 and from August 1996 to July 1997 were analyzed. The reproductive cycle was monitored by using histological analysis. Five gonadal stages were described according to cell types present in the gonad; undetermined, gametogenesis, maturity, spawning and post-spawning. This holothurian reproduces annually during summer (July to September), when sea surface temperature reaches 27 °C. The gonad index is related to the gonadal stages. The first sexual maturity for I. fuscus was calculated at 367 g (4 to 5 years old) according to the von Bertalanffy equation, and nearly all the specimens at Isla Espíritu Santo were 5 to 7 years old (including some individuals over 35 years old). Data of the length–weight relationship showed that I. fuscus grows allometrically at the studied site (b = 1.83). The mortality rate was relatively high (M = 0.51), indicating that in a typical cohort, 40% of the recruits does not survive the first year, and less than 20% reaches maturity. Received: 15 July 1998 / Accepted: 19 August 1999     

Reproductive variability over a four-year period in the sea urchin Evechinus chloroticus (Echinoidea: Echinodermata) from differing habitats in New Zealand

 The endemic New Zealand echinoid, Evechinus chloroticus (Valenciennes), was sampled approximately monthly from September 1990 to October 1994 at three sites in Tory Channel, Marlborough Sounds, New Zealand. These channel sites (outer, mid and inner) were up to 20 km from the open ocean and differed in their shore type, exposure to wave action and macrophyte abundance. E. chloroticus showed an annual reproductive cycle at each site, with gametogenesis commencing in the late austral winter and spawning in summer. Maximum gonad indices (reproductive potential) varied spatially, with the outer site generally having higher maximum gonad indices than the inner site, and temporally, with maximum gonad indices occurring earlier in 3 of the 4 seasons at the outer site than the inner site. The mid and inner sites showed much greater variation in maximum gonad indices (range 15.83 to 26.99% and 11.87 to 20.90%, respectively) than the outer site (range 19.31 to 22.95%). Reproductive output (weight of gametes released per gram echinoid) also varied, with the different sites showing significantly different outputs in the different years. A regression of maximum reproductive potential against reproductive output was significant ( p < 0.001), and had a positive slope with an r ² of 0.79. While, the initiation of gametogenesis was relatively synchronous between sites and years, and is possibly cued by increasing daylength, it progressed at different rates among populations. Spawning did show spatial and temporal variability, occurring near the time of highest sea-surface temperatures (∼15 °C). The observed variations in reproductive cycle may be related to small-scale variability in diet and environmental conditions. Furthermore, asynchronous spawning, variable spawning duration, and variable reproductive output are likely to strongly influence annual recruitment variability in E. chloroticus, with different larval subpopulations contributing unequally in different years. The ecological consequences of this, both for the ability of E. chloroticus to propagate itself in space and time and for the management of the developing E. chloroticus fishery in New Zealand, are discussed. Received: 9 December 1998 / Accepted: 13 June 2000     

Effects of organochlorines on the ultrastructure of the liver of the damselfish Parma microlepis from reefs in New South Wales, Australia

  Parma microlepis (Günther) were collected from Malabar, an urban location close to the centre of Sydney, Australia, and from Jervis Bay, a reference location 170 km south of the city centre. At each location, fish were collected from two sites separated by 100 to 200 m. The ultrastructure of normal liver tissue is described based on 20 female fish collected from Jervis Bay, where fish are known to be exposed to low levels of organochlorine contaminants. Alterations in the endoplasmic reticulum, mitochondria, lysosomes and nuclei of hepatocytes were identified and quantified in the liver tissue of fish from this location and compared to alterations in 20 female fish collected from Malabar, where fish are exposed to higher concentrations of organochlorine pesticides such as DDT compounds. There were significant differences in the percentage of hepatocytes with swollen mitochondria (F = 124.025, df = 2, 2, P = 0.008) and atypical nuclei (F = 22.198, df = 2, 2, P = 0.043) between sites (100 to 200 m apart), but there were no clear differences between the percentage of structural alterations in the hepatocytes of P. microlepis from Jervis Bay and Malabar. Associations between liver morphology and the organochlorines aldrin, dieldrin, DDE and chlordane were examined using a Pearson correlation matrix. Significant correlations were detected between the percentage of hepatocytes with dilated endoplasmic reticulum and the concentrations of the pesticide aldrin (r = 0.600, df = 11, r _{crit(α = 0.05)} = 0.553). Significant associations were also detected between the percentage of hepatocytes with disorganised endoplasmic reticulum and the concentrations of dieldrin and DDE residues in fish (r = 0.576, r = 0.567, respectively, df = 13, r _{crit (α = 0.05)} = 0.514). However, there was little evidence that ultrastructural alterations in fish responded to increasing concentrations of these pesticides in a consistent dose-response manner. Received: 20 October 1998 / Accepted: 24 November 1999     

Reproductive biology of the antipatharian black coral Antipathes fiordensis in Doubtful Sound, Fiordland, New Zealand

The reproductive biology of Antipathes fiordensis Grange, a species endemic to south-western New Zealand, was followed from April 1994 to May 1995. Ten colonies were individually tagged in Doubtful Sound and sampled on a monthly basis in order to determine their reproductive activity. The fecundity of each of the five tagged female colonies was determined by estimating the total number of polyps per colony from photographs of each colony and by planimetry, the proportion of gravid polyps per colony, and the mean number of oocytes per gravid polyp. In addition, 56 colonies were sampled in March 1995 to estimate the sex ratio, height at sexual maturity, and mean sizes of females and males. A. fiordensis was found to be a dioecious species which, in the absence of gonads in the polyps, has no obvious external morphological differences between the sexes. Broadcast spawning of gametes is the likely mode of reproduction. Gametogenesis began in November 1994 and was highly synchronous within and between colonies, with spawning occurring in March 1995. The sex ratio in adults was 1:1. Colonies reached sexual maturity between the heights of 70 and 105 cm which, based on existing estimates of growth rate, corresponds to a minimum age for sexual maturity of about 31 yr. The largest oocytes measured ranged from 100 to 140 μm in size. Female colonies produced between 1.3 and 16.9 million oocytes, with the larger colonies dominating the reproductive output of the population. Received: 23 June 1997 / Accepted: 1 August 1997