Spawning Patterns Research Articles

Reproductive cycle and spawning patterns of Lizardfish, Saurida tumbil (Bloch, 1795) in southern water of Iran

Reproductive activity of lizard fish, Saurida tumbil was assessed using histology. Sex ratio, maturation cycle, fecundity, gonadosomatic index based on 949 specimens collected monthly from north coast of Persian Gulf (Hormuzgan province), between June 2007 to June 2008. The sex ratio of the investigated fish was 1.92:1 (females: males). The results showed that the total length of female specimens ranged from 16.2 to 55.5 cm and total weight extended from 29.93 to 1587.12 g, while male specimen ranged from 18.1 to 44.00 cm and from 30.81 to 724.00g in total length and total weight respectively. The length-weight relationship valued for females and males were Wtot=0.0017L3.4214 R2=0.9578 and Wtot=0.0018L3.4015 R2=0.9699, respectively. Different stages of gonad development based on external appearance and histological observation of ovaries, revealed the existence of six stages for oocyte development of female specimens as immature, maturing, ripening, ripe, spawning and spent. The mean monthly values of GSI indicated that the species is a spring and autumn spawner with two peaks from September to November and a minor peak from February to April. Mean length at first maturity (Lm 50%) was 27.4 cm for females and 25.3 cm for males. Absolute fecundity of 30 maturity samples ranged between 48863-211689 as the number of eggs found in each ovary in the size range 40-50 cm.

Application of GAMs and multinomial models to assess the spawning pattern of fishes with daily spawning synchronicity: A case study in the European anchovy (Engraulis encrasicolus) in the central Mediterranean Sea

Information on the breeding behaviour of fish such as spatial segregation phenomena during spawning events is important both for understanding their reproductive ecology but also for correctly designing sampling schemes in stock assessment. The daily spawning pattern of the European anchovy, Engraulis encrasicolus, was assessed using a novel methodology that included the analysis of the hourly distribution of imminent and recent spawning stages using a combination of generalised additive models (GAMs) and of multinomial models for ordinal categorical data. To do so we used data from nine years of daily egg production method, DEPM, surveys, carried out in the Strait of Sicily. The spatial distribution and occurrence of actively spawning individuals were also analysed. Results showed that the actively spawning phase period (ASPP), i.e., the period from the onset of oocyte hydration to spawning ranged approximately 4.5h between ca. 18:30 and 23:00 while a daily spawning peak was identified at 22:30. The sex ratio was skewed during the ASPP such that females exceeded males by ca. 20% at mid ASPP. During the ASPP the proportion of Day-0 females (i.e., females that spawned or would spawn the day of sampling) decreases with increasing bottom depth while outside the ASPP Day-0 spawners did not show any particular bathymetric pattern. In the study area, anchovies exhibit segregative spawning behaviour which drives spawners to select shallower waters, similar to other anchovy populations in the Mediterranean while in the Atlantic and in other clupeoid populations the opposite bathymetric trend has been observed.

Have the spawning habitat preferences of anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax) in the southern Benguela changed in recent years?

AbstractThis paper examines whether the ranges of occurrence of anchovy and sardine eggs have changed off the South African coast in recent years, and whether this could be linked to changes in sea surface temperature (SST). We used a single parameter quotient analysis with randomization to estimate the preferred and tolerated SST ranges of the spawning habitats of anchovy and sardine in the southern Benguela over the period 1988–2009. Previous studies have reported long‐term change in SST off the South African coast, and our analysis was aimed at determining whether spawning habitat selection by these small pelagic fish tracked such change. The analysis used data on egg occurrence collected concurrently with in situ SST data during annual surveys of pelagic fish biomass conducted along the South African coast. Results show that anchovy typically, but not always, spawn in warmer waters (17.0–23.0°C) than sardine do (16.0–22.0°C), and sardine almost always showed a wider SST tolerance range than did anchovy, over the time‐series. The analysis further suggests evidence of an increase in the surface temperature conditions along the South African coast recently; the spawning patterns of anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax) appear to track these changes through time. Therefore, the spawning habitat preferences of anchovy and sardine in the southern Benguela have changed in recent years, but this is unlikely to be due to warming alone.

Temporal trends in condition and reproduction of quagga mussels (Dreissena rostriformis bugensis) in southern Lake Michigan

Currently little is known about the condition and spawning patterns of quagga mussels (Dreissena rostriformis bugensis) in deeper, consistently cold regions of the Great Lakes. This lack of information limits our ability to predict the future expansion of D. r. bugensis in the offshore regions of the Great Lakes and other large, deep lakes. We collected quagga mussels on a monthly basis in 2013 (April–September) at three established sites along a depth transect (25, 45, and 93 m) in southern Lake Michigan and calculated a condition index (CI), a ratio of dry soft tissue weight to internal shell capacity, to assess condition, and a gametogenic index to assess reproductive activity. We also measured size–frequency, density, and biomass in March, July, and October. Condition was consistently highest at 25 m, population biomass and average shell length were highest at 45 m, and density was highest at 93 m. At all three depths, CI decreased with increasing shell length suggesting that food availability may be limiting for larger individuals. Mussels at 45 m spawned earliest with over 50% spent by July while mussels at 93 m began spawning in August. Mussels at 25 m had not yet spawned by September. Long-term trends in density indicate that D. r. bugensis populations continued to expand at the 93 m site but may be stabilizing at 25 m and 45 m. Consistent with density trends, CI at 25 m and 45 m was lower than in 2004 and 2008.

Reproductive biology characteristics of red mullet (Mullus barbatusL., 1758) in Southern Adriatic Sea and management implications

The main important reproductive aspects of Mullus barbatus , one of the most important target species for the fishery in the Mediterranean basin, have been studied on the basis of MEDITS trawl survey and sampling of commercial landing. The total length (TL) of females has been demonstrated to be positively correlated with egg sizes and plasmatic concentration of vitellogenin. The possible implications of these aspects on the management of red mullet resources are discussed in this work. Moreover, the relationship between TL and fecundity follows an exponential pattern with a temporal trend during the spawning season. These results represent an important input for more effective management measures, such as the seasonal closure of fishery in summertime. The frequency distribution of the oocytes’ diameters showed an asynchronous ovarian organization with batch spawning pattern. Monthly variations in the gonadosomatic index and maturity stages percentage showed that males spawn during almost the entire year showed an increasing trend from November to June and a decreasing trend from July to October, while females in spawning phase are recorded from April to July, with peaks in May and June. The length at 50% maturity (L50) estimated respectively for females and males are 12.1 cm (±0.083) and 10.1 cm (±0.073).

Multi-species spawning synchrony within scleractinian coral assemblages in the Red Sea

Early work on coral reproduction in the far northern Red Sea suggested that the spawning times of ecologically abundant species did not overlap, unlike on the Great Barrier Reef where many species spawn with high synchrony. In contrast, recent work in the northern and central Red Sea indicates a high degree of synchrony in the reproductive condition of Acropora species: over 90 % of species sampled in April/May contain mature gametes. However, it has yet to be determined when most Acropora release their gametes. In addition, there is a lack of data for other ecologically important scleractinian species such as merulinids and poritids. Here, we document the date and time of spawning for 51 species in the central Red Sea over three consecutive years, and the month of spawning for an additional 17 species inferred from the presence of mature gametes. Spawning occurs on nights around the full moon, the spawning season lasts at least 4 months from April until July, and observations are consistent with the few other records from the Red Sea. The number of Acropora species spawning was highest in April with 13 species spawning two nights before the full moon in 2011, 13 species spawning on the night of the full moon in 2012, and eight species spawning four nights after the full moon in 2013. The total number of species spawning was high in April, May, and June and involved 15-19 species per month in 2012. Only four species spawned in July 2012. Few regions worldwide have been similarly sampled and include the Philippines, Okinawa in Japan, and Palau, where spawning patterns are very similar to those in the central Red Sea and where corals spawn on nights around the full moon over a period of 3-4 months. In particular, in all four locations, Acropora are among the first species to spawn. Our results add to a growing body of evidence indicating that multi-species spawning synchrony is a feature of all speciose coral assemblages.

Tácticas reproductivas para optimizan la supervivencia de la descendencia de Cichlasoma orientale (Perciformes: Cichlidae)

High mortality rates have been observed in Teleost during early developmental stages, as well as great variations in reproductive tactics, which are related to adaptations towards environmental conditions and ecological niches for which different species have a specific response. The objective of this study was to describe reproductive tactics related to the survival of Cichlasoma orientale offspring, including aspects of body size, parental care, fecundity, oocyte size and spawning patterns. Samples were performed monthly from August 2011 to July 2013, in lentic and lotic environments at Curu river basin, Brazilian Northeastern semiarid region. Individual behavior (n = 13) was observed underwater for over 50 hours by ad libitum sampling and focal-animal sampling. Collected individuals (males n = 185, females n = 95) were evaluated regarding the standard length, batch fecundity, oocyte size and spawning pattern. In females with mature ovaries, oocyte groups at different developmental stages were observed, these cells were counted and measured, and fecundity was estimated by the gravimetric method. Our results showed that the species displayed biparental care behavior and, on average, males were larger than females. Based on 46 ovaries, the average batch fecundity was 2,052-849 (range: 254-3 389). Standard length and batch fecundity were positively correlated, but no correlation was found between oocyte size and standard length. The maximum diameter observed in the most developed oocytes was 1.8 mm. The observed distribution of oocyte size classes indicated synchronous oocyte development in three groups: pre- vitellogenic, vitellogenic and mature, showing that C. orientale is a multiple spawner. Differences in the amount of oocytes among the three groups were observed, with the most developed group showing the smallest number of oocytes. The combination of low fecundity and large egg size is characteristic of demersal spawners due to a greater environmental stability. Multiple spawning increases chances of survival mainly because of increased fecundity per reproductive season, and the reduced competition among the offspring. We concluded that C. orientale makes a heavy investment in larval survival in detriment of the offspring number. Survival is favored by the large size of oocytes, large yolk reserve, biparental care and multiple spawning pattern.

Identifying Spawning Events of the Sea ScallopPlacopecten magellanicuson Georges Bank

ABSTRACT Georges Bank is the most productive sea scallop fishing ground in the world, but little is known about the regional spawning patterns. The sea scallop rotational management plan is based on yield projections estimated from shell height/meat weight relationships. Semiannual spawning may influence yield projections, impacting fishery allocations. This study identifies spawning events at two locations on Georges Bank: one in Closed Area I (CAI) and the other in Closed Area II (CAII). We hypothesize that spawning is semiannual, spring spawning is incomplete compared with autumn spawning, and reproductive stage differs temporally between areas. Scallops (n = 1,871) were collected during a monthly dredge survey in these two areas from two sites from March 2011 through June 2013. Tissues from scallops (shell height ∼130 mm) frozen at sea, were oven-dried and the gonosomatic indices (GSIs) were analyzed to identify spawning events. Oocyte diameter was measured to determine maturity. Bottom temperature wa...

Determination of Temporal Spawning Patterns and Hatching Time in Response to Temperature of Atlantic Bluefin Tuna (Thunnus thynnus) in the Western Mediterranean

This study analysed the temporal pattern of Atlantic bluefin tuna (ABFT) spawning in the Balearic spawning ground and examined its reproductive performance after years in captivity. Furthermore, ABFT hatching time at different on-site temperatures was determined for the first time. Spawning surveys were carried out in 4 spawning seasons (2009–2012) aboard tuna transport vessels. Three groups of spawners were monitored: a captive group transported to the spawning region and monitored throughout the four spawning seasons and two wild groups caught in 2009 and 2010 which were transferred to a monitoring transport cage immediately after being caught. Surface plankton samples were collected nightly, beginning immediately after the first purse seine catches were made and concluding after spawning was observed to have ended. All groups displayed the same spawning hours, restricted between 2:00–5:00 a.m. The captive group, as they got older, shifted towards the earliest hour, suggesting an age influence on reproductive time. The onset of spawning varied annually from the end of May to the beginning of June at temperatures around 19°C–20°C, ending by the second week of July. The peak of spawning was consistently around the summer solstice, June 15th–30th. The results showed the negative effect of unstable oceanographic conditions in the spawning process which might influence the annual reproductive success of ABFT. The influence of temperature on hatching time was higher than that observed in other tuna species, twice as fast at 26°C (23 h) as at 19.5°C (49 h). Overall, this study shows the strength of the internal mechanism in ABFT that controls spawning traits. Spawning in ABFT is cyclical and highly synchronised on diel and annual scales. We consider that the timing of spawning is rather influenced by day length and its adaptive significance is discussed.

Physico-Chemical Characteristics of Kottakudi and Nari Backwaters, South East of Tamil Nadu

The study of physico-chemical properties of coastal environments is important, because the variations in the physicochemical properties were influence on the floral and faunal production. During the study period, the maximum and minimum values of rainfall, water temperatures, salinity and dissolved oxygen recorded were 16.76mm to 745.76mm, 24 to 33°C, 24 to 37% and 3.8 to 4.6 ml/l for both the stations. And the dissolved nutrients of nitrite, nitrate, ammonia, inorganic phosphate and reactive silicate recorded were 0.83 to 5.62 μM, 10.3 to 25.6 μM, 0.11 to 5.62 μM, 0.52 to 3.76 μM and 30 to 123 μM for both the stations respectively. The variable of physico-chemical parameters is mainly affect the species diversity, pattern of diversity, reproduction, spawning, survival and other activities. To maintain optimum level of water quality parameters this is better to species survival and healthy ecosystem.

A Legacy of Divergent Fishery Management Regimes and the Resilience of Rainbow and Cutthroat Trout Populations in Lake Crescent, Olympic National Park, Washington

Abstract As a means to increase visitation, early fisheries management in the National Park Service (NPS) promoted sport harvest and hatchery supplementation. Today, NPS management objectives focus on the preservation of native fish. We summarized management regimes of Olympic National Park's Lake Crescent, which included decades of liberal sport harvest and hatchery releases of 14.3 million salmonids. Notably, nonnative species failed to persist in the lake. Complementary analyses of annual redd counts (1989–2012) and genetics data delineated three sympatric trout (one rainbow; two cutthroat) populations that exhibited distinct spatial and temporal spawning patterns, variable emergence timings, and genetic distinctiveness. Allacustrine rainbow trout spawned in the lake outlet from January to May. Cutthroat trout spawned in the major inlet tributary (Barnes Creek) from February to June and in the outlet river (Lyre) from September to March, an unusual timing for coastal cutthroat trout. Redd counts for ea...

Simulation of fishery-induced changes on the reproductive cycle of common sardine, Strangomera bentincki, off central southern Chile

Intense fishing mortality generates changes in marine populations and ecosystems, and an increase in the sensitivity to environmental changes. Fishery-induced demographic changes are the main mechanisms involved due to truncation of age structure of a population trough selective removal of larger and older fish from a population. As a consequence, changes in the seasonal spawning pattern can occur because larger and older fish tend to have a longer and more extensive reproductive activity than smaller and first-time spawners. This is the case of a small pelagic fish, known as the common sardine Strangomera bentincki, which supports an important fish activity off central southern Chile (33°S-41°30′ S). In this paper, fishery-induced changes on the seasonal reproductive cycle of common sardine were simulated through an age-structured population dynamics on a monthly basis. The fishery is dependent on the annual pulse of recruitment and fishing efforts are applied intensively on the juvenile fraction during the first half of each year. Thus, fishing mortality removes fast growing fish or fish recruiting earlier, and thereafter the age structure tends to be truncated, and as a consequence, slow-growing fish or late-recruiting fish could be selected in the population. A delayed peak in the reproductive cycle was observed in the gonadosomatic index during the period 2000–2010, as compared with the period 1993–1999. In addition, a change in the length composition of the catches was observed, supporting the results obtained with simulations. The fishery-induced changes on the reproductive cycle of common sardine can increase the sensitivity of the population to climate variability either matching or mismatching the reproductive cycle with favorable/unfavorable environmental variables for recruitment.

Spawning phenology and geography of Aleutian Islands and eastern Bering Sea Pacific cod (Gadus macrocephalus)

Pacific cod (Gadus macrocephalus) is an economically and ecologically important species in the southeastern Bering Sea and Aleutian Islands, yet little is known about the spawning dynamics of Pacific cod in these regions. To address this knowledge gap, we applied a gross anatomical maturity key for Pacific cod to describe temporal and spatial patterns of reproductive status over three winter spawning seasons: 2005, 2006, and 2007. Maturity status of female Pacific cod was assessed by fishery observers during sampling of commercial catches and used to construct maps showing spawning activity in the Bering Sea and Aleutian Islands. Most spawning activity was observed on the Bering Sea shelf and Aleutian Island plateaus between 100 and 200m depth. Data for those days when a high percentage of spawning stage fish were observed were used to identify areas with concentrations of spawning fish. Spawning concentrations were identified north of Unimak Island, in the vicinity of the Pribilof Islands, at the shelf break near Zhemchug Canyon, and adjacent to islands in the central and western Aleutian Islands along the continental shelf. The spawning season was found to begin in the last days of February or early March and extend through early to mid-April. Variation in spawning time (averaging ~10 days between years) may have been associated with a change from warm (2005) to cold (2007) climate conditions during the study period. Our information on Pacific cod spawning patterns will help inform fishery management decisions, models of spawning and larval dispersal and the spatial structure of the stock.

Batch fecundity and spawning frequency of invasive Hemiculter leucisculus (Basilewsky, 1855) in Erhai Lake, China

Hemiculter leucisculus are multiple spawners with indeterminate fecundity, although previous fecundity estimates have assumed a determinate spawning pattern. Batch fecundity and spawning frequency of H. leucisculus were studied in Erhai Lake, China, in which the fish, as an exotic species, has become a successful colonizer. Spawning frequency was 16.05 %, as determined from the percent of females with postovulatory follicles 12 to 36 h old during the peak reproductive period (from May 27 to August 8). The average interval between spawning was 6.2 days and there were more than 16 total spawning batches during the peak reproductive period. The average batch fecundity (mean ± SD) was 11,934 ± 5,921 hydrated oocytes in 40 females (standard length or SL: 9.1–14.4 cm), while relative batch fecundity was 560 ± 137 eggs g−1 wet weight. The total potential annual fecundity was approximately 190,944 oocytes over the whole spawning season and was much higher than the estimated standing stock (31,585 oocytes) of yolked oocytes (36 females, SL: 9.5–16.2 cm) at the beginning of the spawning season in April 2010. This high annual fecundity is likely to have contributed to successful invasion of Erhai Lake by H. leucisculus.

Reproduction strategies and population dynamics of two Diogenes hermit crabs (Superfamily: Paguroidea) in a tropical mangrove estuary

Two species of sympatric hermit crab, Diogenes moosai Rahayu & Forest, 1995 and D. lopochir Morgan, 1989, spatially defined in the Matang mangrove estuary, and facing high mortality due to tidal emersion, predation and competition are hypothesised to adopt different reproductive strategies for successful recruitment. The crabs were sampled by a small otter trawl at mid-estuary, river mouth, mudflat and shoal area along the estuary to adjacent coastal area. Diogenes moosai was widespread in the mudflat as well as in the subtidal shoal area where D. lopochir was dominant. Diogenes moosai showed year-round reproduction, whereas D. lopochir a discontinuous spawning pattern. Major reproduction in both species, however, occurred in January/February and July which resulted in two major recruitment pulses in a year. Diogenes moosai also suffered very high mortality resulting from cockle harvesting on the mudflat, twice that of D. lopochir. Our results show that the more widespread species at higher risk of exposure to extreme physical conditions (in the mudflat), predation and competition for shell resources, generally spreads its reproduction over the year, while the dominantly subtidal species at greater risk of predation only reproduces less regularly but at the most favourable period.

Laboratory Spawning Patterns of Mummichogs,Fundulus heteroclitus(Cyprinodontiformes: Fundulidae)

The common estuarine fish species Fundulus heteroclitus or Mummichog has long been used in ecotoxicological studies; however, their periodic spawning pattern is perceived to limit their use in reproductive bioassays and the availability of sensitive life stages. This study evaluated the lunar periodicity of spawning, egg production, and changes in gonadosomatic index (IG) in the laboratory using wild and F1-generation Mummichogs that originated from three different geographic areas: the northern extreme part of their geographic range (New Brunswick, Canada; 45°N), the middle of the northern subspecies range (Massachusetts, USA; 41°N), and within the southern subspecies range (Virginia, USA; 37°N). Unlike some previous studies of wild and laboratory-held fish, Mummichogs from all locations were continuous spawners over a prolonged period of time (8+ weeks) under laboratory conditions. However, there was greater variance in egg production in smaller fish (≤70 mm total length) compared to larger fish. Our re...

Reproducción del atún de aleta negra <i>Thunnus atlanticus</i> (Perciformes: Scombridae) en el Archipiélago San Pedro y San Pablo, Atlántico Ecuatorial, Brasil

The reproduction of Blackfin tuna Thunnus atlanticus has been described for coastal regions, and for a long time, this species was considered to be a strictly continental spawner. Recently, this species was observed around a seamount habitat 500 nautical miles Northeast of Brazil, located between South America and Africa. In this study we describe the reproductive biology of Blackfin tuna at Saint Peter and Saint Paul Archipelago (SPSPA). Male and female gonads were sampled from December 2008 to July 2010, and analyzed macro and microscopically. A total of 361 fish were sampled (247 males and 114 females). Males were more common than females, with a sex ratio of 2.2 male:1 female. The fork length (FL) of all sampled specimens ranged from 38 to 98cm, and larger length classes were more frequent in males. It was possible to distinguish six maturity phases for females: immature, developing, spawning capable, actively spawning, regressing and recovering. Five phases were identified for males: immature, developing, spawning capable, actively spawning and recovering. The gonad index (GI) mean monthly values ranged from 6.6 (SD = 4.1) to 58.4 (SD = 34.7) for females, and from 2.6 (SD = 1.3) to 66.2 (SD = 30.4) for males. For both sexes, the largest GI values were observed at the beginning of the first semester of the year. Size at first maturity was estimated at 48cm FL and 55cm FL for females and males respectively. Approximately 80% of the specimens were adults and considered to be in reproductive conditions. Histological analysis of the ovaries and testes showed that most of the specimens were sexually mature and were reproductively active during all months of the year. However, females with mature ovaries, with large amounts of hydrated oocytes and post-ovulatory follicles, were mainly found from December to March, thus these months may constitute the main spawning season in SPSPA. Batch fecundity varied between 272025 and 1,140584 oocytes for 56 and 68 cm FL females respectively. Oocyte development and spawning patterns suggest a multiple spawning behavior. The results revealed that Blackfin tuna is using the SPSPA as a spawning ground, similar to other species commonly observed in the same area during the same reproductive season.

Reproductive biology and recruitment of the deep-sea fish community from the NW Mediterranean continental margin

Temporal patterns in deep-sea fish reproduction are presently unknown for the majority of deep continental margins. A series of seasonal trawling surveys between depths of 300 to 1750m in the Blanes submarine canyon and its adjacent open slope (NW Mediterranean) were conducted. The bathymetric size distributions and reproductive cycles of the most abundant species along the NW Mediterranean margin were analyzed to assess the occurrence of (i) temporal patterns in reproduction (i.e., spawning season) along a bathymetric gradient and (ii) preferential depth strata for recruitment. The fish assemblages were grouped in relation to their bathymetric distribution: upper slope, middle slope and lower slope species. Middle-slope species (i.e., 800–1350m) showed short (i.e., highly seasonal) reproductive activity compared to the upper (300–800m) and lower (1350–1750m) ones. Our results, together with those previously published for megabenthic crustacean decapods in the area, suggest a cross-phyla depth-related trend of seasonality in reproduction. In the middle and lower slope species, the reproductive activity reached a maximum in the autumn–winter months and decreased in the spring. The observed seasonal spawning patterns appear to be ultimately correlated with changes in the downward transport of organic particles and with seasonal changes in the physicochemical characteristics of the surrounding water masses. The distribution of juveniles was associated with the bathymetric stratum where intermediate nepheloid layers interact with the continental margins, indicating that this stratum acts as a deep-sea fish nursery area.

Mating behaviour and general spawning patterns of the southern dumpling squid Euprymna tasmanica (Sepiolidae): a laboratory study

We provide the first detailed description of mating behaviour and multiple mating in the southern dumpling squid, Euprymna tasmanica (Pfeffer, 1884) in the laboratory, as well as details on their general spawning patterns. We found that male E. tasmanica increase the number of ‘pumps’ (mantle contractions) when mating with females that had recently mated, showing that males are able to determine the recent mating history of females. We also found that at the conclusion of mating, the male’s hectocotylus was enlarged. To our knowledge, neither had previously been described in sepiolid squid. Euprymna tasmanica females lay multiple clutches over a large proportion of their lifespan, from 1 to 121 d. There was a considerable variation in the number of eggs produced per female in captivity, ranging from 6 to 646 eggs, and in the number of eggs per clutch, from 6 to 163 eggs. Egg number per clutch declined significantly over the spawning period. Larger females produced larger hatchlings, and egg mass and hatchling mass were significantly correlated. At higher ambient water temperatures the rate at which females produced clutches increased and the size of the eggs laid decreased.

Fecundity, oogenesis, and ovulation pattern of southern African Lycoteuthis lorigera (Steenstrup, 1875)

Lycoteuthis lorigera is among the most abundant mesopelagic squid on the continental slope of the south Atlantic. It is the dominant prey in some commercially harvested groundfish. Despite its abundance and importance in the mesopelagic foodweb, its general biology is poorly known. In this study, the spawning pattern and fecundity of L. lorigera from southern African waters were investigated. Both histological examination and length frequency analysis of ovaries in various stages of development revealed that the ovulation pattern of L. lorigera is asynchronous, which indicates a spawning strategy where batches of eggs are spawned repeatedly over time. More specifically, ovulation is group synchronous, where distinct batches of 1,200–2,400 eggs ripen in the ovary and accumulate in the oviducts. The potential fecundity was estimated to be 20,000–50,000 in immature females (n = 6) and 8,000–25,000 in mature females (n = 21). The number of ripe eggs in the oviducts suggests that batches of spawned egg masses contain between 1,000 and 4,000 eggs. The reproductive strategy of L. lorigera is discussed and compared to the reproductive strategies of oceanic squid inhabiting the continental slope of southern Africa.