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Growth and reproduction of Megabalanus tintinnabulum (Crustacea: Cirripedia) in coastal waters of Pakistan, North Arabian Sea
Abstract
The growth and reproductive/ brooding pattern of Megabalanus tintinnabulum were studied from January 2012 to December 2013 on two rocky shores, Buleji and Manora, Karachi, the northern Arabian Sea. Population parameters were estimated using the von Bertalanffy growth function (VBGF) and ELEFAN 1 with the aid of FiSAT software. The population of M. tintinnabulum showed variability in density, size and growth rates between two rocky shores. The average density of M. tintinnabulum was higher at Buleji (101.9 ± 15.02 individual m⁻²) than Manora (76.0 ± 8.05 individual m⁻²). Though the estimated asymptotic length (L∞) of M. tintinnabulum was 51.98 mm at both sites, the growth coefficient (K) value was higher at Manora (0.63 year −1) than Buleji (0.44 year −1). The population of M. tintinnabulum grew at a faster rate attaining the length of 31.8 mm in one year at Manora as compared to length of 23.7 mm at Buelji. Longevity in M. tintinnabulum was 4.3 years at Manora and 6.4 years at Buleji, while the natural mortality rate (M) was 1.131 year−1 and 0.894 year−1 at Manora and Buleji, respectively. Though mature ovaries and testes were found throughout the year but the brooding individuals were observed during the winter (November to February) period showing that lower temperatures (20-24 ºC) are preferred over higher temperatures (29-34 ºC). The brooding capacity was same at two rocky shores but the numbers of brooders were higher at Manora than Buleji. The reproductive capacity was 7,914 ± 303 of eggs per brood.
... Among the more straightforward traits to describe, the population size structure is underreported for barnacles in general. For Megabalanus, there are only a few accounts of the size structure of populations on natural substrates (Ali and Ayub 2021), with no reports from the endemic regions range of M. coccopoma, given that the endemic range of M. tintinnabulum is not known. ...
... Data on the maximum size of species is also elusive. For instance, for M. tintinnabulum, there are only three documented measurements by Karande and Palekar (1966), Annadale (1911) and, more recently with Ali and Ayub (2021) Estimations of growth in historical records are often based on the size of organisms after known events. For instance, Darwin (1854) deduced the growth of M. tintinnabulum from Samuel Stutchbury's observation of specimens approximately 5 cm in basal diameter on a vessel at sea for only a year. ...
... Apolinario (2001Apolinario ( , 2003 investigated the recruitment and reproduction of M. coccopoma and M. tintinnabulum in southeastern Brazil. Ali and Ayub (2021) explored growth and reproduction of M. tintinnabulum in Pakistan. For Megabalanus azoricus (Pilsbry 1916) Pham et al. (2011) described the recruitment, growth, and Dionisio et al. (2007) its reproductive biology, respectively. ...
Introductions of close related species provides an opportunity to study differences in life history traits and their ability to cooccur in syntopy. We examine a case in which three species of Megabalanus barnacles coexist syntopically along the tropical southwestern Atlantic. A comparative life history study, focusing on parameters such as size, distribution, abundance, growth, and reproduction is presented. Through such an analysis, we could better understand the successful establishment of the non-indigenous M. coccopoma in the southwestern Atlantic, discern why the cryptogenic M. tintinnabulum flourishes across approximately 5000 km of Brazilian shores, and probe how the endemic M. vesiculosus occurs with these two species. Although we did not measure growth and reproduction period, the higher egg size and fecundity of M. vesiculosus might be allowing its extensive range of occurrence. The observed superior density of M. coccopoma in southern locations might be directly associated with its continuous reproduction period and fecundity. But the absence of M. coccopoma on northern shores can be attributed to the smaller egg size, not work wheel on oligotrophic warm water. The faster growth rate and large adult size of M. tintinnabulum appear to be beneficial in competitive intertidal environments of tropical shores. This study showed how close related species diverge in traits, and how such differences may act when in syntopy. The knowledge of how these factors relate to the establishment of nonindigenous species may furnish tools to understand future invasion scenarios.
... In the Arabian Sea, barnacles breed at lower temperatures, i.e., less than 24°C in winter vs. > 28°C in summer; and grow at a rate of 0.44-0.63 mm/year (Ali and Ayub, 2021). ...
Each individual cetacean is an ecosystem itself, potentially harboring a great variety of animals that travel with it. Despite being often despised or overlooked, many of these epizoites have been proven to be suitable bio-indicators of their cetacean hosts, informing on health status, social interactions, migration patterns, population structure or phylogeography. Moreover, epizoites are advantageous over internal parasites in that many of them can be detected by direct observation (e.g., boat surveys), thus no capture or dissection of cetaceans are necessary. Previous reviews of epizoites of cetaceans have focused on specific geographical areas, cetacean species or epibiotic taxa, but fall short to include the increasing number of records and scientific findings about these animals. Here we present an updated review of all records of associations between cetaceans and their epibiotic fauna (i.e., commensals, ecto- or mesoparasites, and mutualists). We gathered nearly 500 publications and found a total of 58 facultative or obligate epibiotic taxa from 11 orders of arthropods, vertebrates, cnidarians, and a nematode that are associated to the external surface of 66 cetacean species around the globe. We also provide information on the use as an indicator species in the literature, if any, and about other relevant traits, such as geographic range, host specificity, genetic data, and life-cycle. We encourage researchers, not only to provide quantitative data (i.e., prevalence, abundance) on the epizoites they find on cetaceans, but also to inform on their absence. The inferences drawn from epizoites can greatly benefit conservation plans of both cetaceans and their epizoites.
The growth and reproductive biology of the limpet Patella aspera were studied in the north-eastern Atlantic, Madeira archipelago, to enhance the knowledge concerning biological parameters and population dynamics of this species. This study comprised the estimation of growth rates, sexual maturity, reproduction, recruitment patterns, mortality coefficients and the exploitation rate, and yield-per-recruit (Y/R) based on monthly shell-length frequency data. A total of 16,941 specimens were sampled from January to December 2015. The relative growth pattern exhibited a negative allometric nature of growth for both sexes. The estimated von Bertalanffy growth parameters showed an asymptotic length of 84.15 mm for females and 80.51 mm for males with a growth coefficient of 0.36 and 0.32 year−1 respectively. P. aspera in this geographical area is a moderately long-lived limpet with a predominance of specimens younger than 3 years old. This species is a winter breeder with a reproductive cycle encompassing three main periods namely development, spawning and resting with a synchronous gametogenesis for both sexes. Gonadal development lasts from October to December, spawning likely occurs from January until April and resting occurs from May to September. The mean size at sexual maturity was determined as 41.78 mm for females and 38.29 mm for males and the length at first capture as 42.62 mm. The recruitment pattern was continuous throughout the year with a major peak identified in March. The natural, fishing and total mortalities were similar between sexes, with fishing mortality exerting greatest pressure on this resource. However, yield-per-recruit analysis showed that the stock of P. aspera, in the study area, is exploited at levels below the fishing mortality that returns maximum sustainable yield. This study revealed that currently the stock of P. aspera is under-exploited, nonetheless due to it’s slow growth and long life, continuous monitoring and the enforcement of the existing harvest regulations must be accomplished if future over-exploitation is to be avoided. Further genetic studies are necessary to establish connectivity of the populations and improve present conservation strategies.
Benthic-pelagic coupling is manifested as the exchange of energy, mass, or nutrients between benthic and pelagic habitats. It plays a prominent role in aquatic ecosystems and it is crucial to functions from nutrient cycling to energy transfer in food webs. Coastal and estuarine ecosystem structure and function is strongly affected by anthropogenic pressures, however there are large gaps in our understanding of the responses of inorganic nutrient and organic matter fluxes between benthic habitats and the water column. We illustrate the varied nature of physical and biological benthic-pelagic coupling processes and their potential sensitivity to three anthropogenic pressures — climate change, nutrient loading, and fishing — using the Baltic Sea as a case study, and summarize current knowledge on the exchange of inorganic nutrients and organic material between habitats. Traditionally measured benthic-pelagic coupling processes (e.g. nutrient exchange and sedimentation of organic material) are to some extent quantifiable but the magnitude and variability of biological processes are rarely assessed, preventing quantitative comparisons. Changing oxygen conditions will continue to have widespread effects on the processes that govern inorganic and organic matter exchange among habitats while climate change and nutrient load reductions may have large effects on organic matter sedimentation. Many biological processes (predation, bioturbation) are expected to be sensitive to anthropogenic drivers but the outcomes for ecosystem function are largely unknown. We emphasize how improved empirical and experimental understanding of benthic-pelagic coupling processes and their variability are necessary to inform models that can quantify the feedbacks among processes and ecosystem responses to a changing world. This article is protected by copyright. All rights reserved.
Tetraclita squamosa and Tetraclita japonica have recently been separated into two species using allozyme and DNA analysis. The morphologies of the two species, however, have not been described fully, resulting in confusion over diagnostic characters and identification. Tetraclita squamosa has greenish parietes and the tergo-scutal flaps are black with two pairs of white spots. Tetraclita japonica has purplish-grey parietes and the tergo-scutal flaps are not patterned. These characters are good for in-situ species identification. The third cirrus of T. japonica possess an additional bidentate-type seta, which is absent from T. squamosa. Results of discriminant function analysis indicate the shape of the parietes and the scutum geometry of T. squamosa and T. japonica show intraspecific variation between sites, indicating they are not diagnostic characters for separating the two species. The basi-scutal angle of the tergum, however, is significantly different between the two species and is useful in...
The recruitment and population structure of the non-indigenous brackish water mytilid Xenostrobus securis (Lamark, 1819), native to Australasia, were studied in the lower reaches of the Kino River, central Japan. Post-larvae > 2 mm in shell length were found exclusively among barnacle stands of Fistulobalanus kondakovi (Tarasov and Zevina, 1957) and algal fronds of Gloiopeltis tenax (Turner) Decaisone, 1842 from January to May and from July to October. Density of the post-larvae was much greater in the latter period than in the former. Small mussels with shell lengths of 2-4 mm settled to the conspecific mussel beds in April and September. Primary and secondary settlements onto different substrates were observed in the early stages of the life cycle. Two or three cohorts were identified in conspecific mussel beds, and they grew at a rate of ca. 1 mm per month. Density in the beds fluctuated monthly and was greater in the lower than in the middle intertidal zone, suggesting greater spatial heterogeneity in density due to predation in the former.
The abundance and distribution of settlers, recruits, and adults of the barnacle Semibalanus balanoides were monitored in the high, mid, and low intertidal zones at two adjacent, but physically and biologically different sites (A and B) on a rocky intertidal shore in Nova Scotia following a rare occurrence of ice scouring. Availability of planktonic cyprid larvae also was measured at site A. There was a strong concordance between cyprid availability and settler density over the main settlement period among intertidal heights, where each was inversely related to intertidal height. Differences in cyprid availability with intertidal height were related to immersion time as the larvae, in general, were uniformly distributed at the water-substratum interface. Settlement rate was strongly correlated with cyprid availability in the low intertidal zone al site A, where most settlement occurred. In all zones at both sites, recruit density at the end of the main settlement period was a positive function of settler density over this period: on average, 79% of the variation in recruit density was explained by settler density over the main settlement period. Adult density and total settler density also tended to be strongly related: 86% (mid zone at site A) and 73% (high zone at site B) of the variation in adult density was explained by total settler density, except where postrecruitment mortality (i.e., predation) was high (e.g., only 1% of the variation in adult density was explained by total settler density in the low zone at site A). Local hydrodynamics, which influences supply and distribution of planktonic larvae, may dictate the distribution of settlers and, ultimately, adults on this shore.
ABsTRACT The reproductive ecology of Chihamalus anisopoma and Tetraclita stalactifera is compared in order to understand how their life histories function in the context of their present environment, and what selective forces might have shaped their life histories. C. anisopoma is common in the lower intertidal of the Gulf of California. It initiates breeding six weeks after settlement; brooding and recruitment is year-round. Growth after settlement is rapid for two months, then slows markedly. Survivorship is fairly constant at all ages. Observations indicate that most mortality results from predatory gastropods, and from intraspecific crowding. T. stalactifera is generally con fined to the upper intertidal. It failed to brood during the study period. The ovarian cycle indicates that brooding would otherwise take place during the summer. The age of first reproduction is estimated at two years. Recruitment of cyprids is strongly seasonal, peaking during August. The growth rate is relatively constant. Survivorship is initially very poor, apparently due to desiccation stress, but improves substantially after four months. An examination of the intertidal positions and life histories of Tetrac/ita and Chihama/us congeners from different coastlines of the world reveals a relative con servatism of life histories, regardless of position in the intertidal. This conservatism is discussed as a general phenomena in Chthamalus and Tetraclita, and is contrasted with the relative diversity exhibited in another genus of barnacles, Ba/anus.
A technique is proposed to determine the individual age of the marine barnacle Balanus rostratus
from epibiosis of the Japanese scallop. Using this technique, we determined the parameters of linear growth and weight of barnacle from different areas of Amurskii Bay, Sea of Japan. In the open part of the bay, the barnacles are larger than in the middle, more polluted, part, where, at the age of 3.5 and 6.5 years, the barnacles had a mean diameter of shell basis of 30.6 and 46.7 mm, respectively, and mean total body weight of 9.5 and 42.6 g, respectively. A live barnacle was registered at the age of 9.5 years. It was found that isolated specimens or barnacles living close to each other grow better than crustaceans living in multi-layer clusters. A comparative analysis of the growth rate of barnacles from epibioses of mussel and scallop showed that by the end of the first year of life, barnacles living under different conditions still have similar sizes. In the following years, the rate of barnacle growth is smaller on mussels; however, it is even smaller in crustaceans living in the fouling of coastal stones and on a pier.
Abstrak: Strombus canarium Linnaeus, 1758 merupakan antara sumber perikanan gastropoda paling utama di perairan Selat Johor, Malaysia. Dalam kajian ini, persampelan dilakukan secara rawak menggunakan kaedah jalur transek, bermula dari Januari hingga Disember 2005. Data panjang cangkerang dibahagikan mengikut jantina dan panjang, dengan sela-kelas 2 mm. Secara keseluruhannya, nisbah jantan kepada betina adalah pada kadar 1:1.73, yang tidak berbeza secara signifikan berbanding nisbah yang dijangka iaitu 1:1 (P > 0.05). Struktur populasi dianalisis menggunakan kaedah 'Length-based Fish Stock Assessment' (LFSA) yang terdapat dalam perisian FiSAT (FAO-ICLARM Stock Assessment Tools). Taburan panjang-berat bulanan kedua-dua subpopulasi siput jantan dan betina bersifat polimodal. Populasi juga didapati menunjukkan ciri-ciri dwimorfisma jantina. Parameter tumbesaran spesifik bagi setiap kohot menunjukkan nilai panjang 'asimptotik' (L∞) dan pemalar tumbesaran (K) yang lebih tinggi bagi siput betina berbanding siput jantan. Nilai min L∞ adalah 62.90 ± 3.68 mm bagi jantan dan 69.73 ± 0.80 mm bagi betina, sementara nilai min K adalah 1.10 ± 0.15/thn bagi jantan dan 1.40 ± 0.10/thn bagi betina. Kadar tumbesaran yang tinggi dan masa bagi mencapai saiz pasaran yang cepat, ditambah dengan keupayaan untuk membiak sepanjang tahun menjadikan siput ini berpotensi besar bagi aktiviti akuakultur. Walau bagaimanapun, kajian lanjut diperlukan dalam menilai kadar tumbesaran sebenar, serta beberapa parameter lain yang penting bagi sesuatu spesies sebelum sebarang tindakan pengkomersialan dapat dilakukan. Abstract: Strombus canarium Linnaeus, 1758 is among the important gastropod fishery within the western Johor Straits, Malaysia. In this study, systematic random samplings using belt transect were conducted from January to December 2005. Shell-length data were grouped into different sexes and length-classes of 2 mm intervals. Overall ratio of males to females was 1:1.73, which was not significantly deviated from the expected 1:1 (P > 0.05). The population structure was analyzed using the Length-based Fish Stock Assessment (LFSA) protocol in FiSAT (FAO-ICLARM Stock Assessment Tools) software package. Both males and females were highly polymodal in monthly length-frequency distributions. Sexual dimorphism was evident within the population. Specific cohort growth parameters found higher asymptotic length (L∞) and growth constant (K) in females compared to the males. The mean L∞ was 62.90 ± 3.68 mm in males and 69.73 ± 0.80 mm in females, while the mean K was 1.10 ± 0.15 yr-1 in males and 1.40 ± 0.10 yr-1 in females. The higher growth rates and faster growth to marketable size, combined with all
This study examined patterns in the distnbution and demography of the barnacle Chthamalus steiiatus (Poli) at different spatial scales in the northwest Mediterranem. Prelirninary data indicated that the abundance and size of barnacles decreased from high-shore to low-shore habitats. The generality of these patterns was investigated at several locations (10s to 100s of km apart), at sev-eral sites within locations (100s to 1000s of m apart) and at different times. Patterns were consistent with the prelirninary observations, despite considerable spatial and temporal variabiiity at smaii and large spatial scales. The foliowing models were proposed to explain the observed patterns: (1) recruit-ment was intnnsicaiiy greater high on the shore, (2) limitation of recruitment due to pre-emption of the substratum was greater low than high on the shore, (3) environmental conditions reduce growth low on the shore, and (4) mortality was greater low on the shore. The predictions of these models were tested by examining patterns of recruitment, growth and mortality of barnacles and avaiiability of free space in relation to height on the shore, at several spatial scales and through time. Successful recruitment of barnacles was observed at different heights on the shore where resident organisms were removed, despite a trend toward a larger number of recruits high on the shore at 1 location (Livorno). Availabii-ity of bare rock for recruitment was greater high on the shore, implying that pre-emption of the sub-stratum was more intense low on the shore. There was no evidence to suggest that barnacles grew faster on the high shore than on the low shore. The opposite pattern was observed for young barnacles in several cases. Mortality rates were generally greater in low-shore than high-shore habitats for young and for adult barnacles. Patterns emerged over a background of considerable spatial and temporal vanation. These results emphasized the importance of pre-emption of space and mortality of juveniles in generating patterns in the distnbution and structure of populations of barnacles on rocky shores in the northwest Mediterranean.
Within Narragansett Bay (Rhode Island) acorn barnacle growth and reproduction is far greater than at nearby open coast locations. At comparable tidal heights, recruits in the Bay grew to nearly twice the basal diameter and had almost ten times the reproductive output compared to recruits on the open coast. Transplant experiments suggest that the high secondary production of Bay barnacles is largely a phenotypic response to high primary production. Within- and among-site patterns in barnacle secondary production associated with enhanced flow velocities were also conspicuous. Barnacles at low tidal heights, in habitats exposed to large tidal currents and in wave-exposed habitats, had higher growth and reproduction than barnacles at higher tidal heights or habitats with lower velocities. Water column food concentrations and fluid velocities both strongly influence barnacle growth and reproduction through their combined effects on the flux of food to individuals. -from Authors
Phytoplankton blooms are known to influence barnacle recruitment and in boreal regions spring blooms work as an important trigger. Close to the west coast of the sub-continent of India, blooms tend to be triggered by breaks in the monsoon and the recurrence of the monsoon after a short break can stress the new recruits. The recruitment of Balanusamphitrite, an acorn barnacle, at Dona Paula Bay at the mouth of Zuari estuary, Goa, India was studied. Observations included variations in recruitment, larval abundance, development and reproduction. Adult conditioning and inter-brood variations were important factors in the larval ecology of this organism. The results indicate that the impulsive release of larvae during breaks between monsoons could be a short-sighted luxury for Balanusamphitrite in these waters. Temporal variations or recruitment failure in such environments can be attributed to inappropriate cue synchronization.
The standing crop of seaweeds was estimated from the intertidal zone of Buleji area, Karachi on five different occasions from 30. 11. 71 to 11. 1. 73. It was found that production of seaweeds was low during the southwest monsoon period but high during the northeast monsoon season. The area of central Buleji was more productive than the eastern part because of the more complicated nature of the former habitat. The range in the average production in this area was from 986.81 to 4652.00 g/m2 for attachd seaweeds and from zero to 11,171.00 g/m2for drift seaweeds. Hypnea musciformis was the most abundant drift species. Some of the abundant attached seaweeds were Ulva fasciata, Cbondria tenuissima, Sargassnm sp., Cystoseira sp. Valoniopsis pachynema.
Although invasive species are widely recognized as a major threat to marine biodiversity, there has been no quantitative global assessment of their impacts and routes of introduction. Here, we report initial results from the first such global assessment. Drawing from over 350 databases and other sources, we synthesized information on 329 marine invasive species, including their distribution, impacts on biodiversity, and introduction pathways. Initial analyses show that only 16% of marine ecoregions have no reported marine invasions, and even that figure may be inflated due to under-reporting. International shipping, followed by aquaculture, represent the major means of introduction. Our geographically referenced and publicly available database provides a framework that can be used to highlight the invasive taxa that are most threatening, as well as to prioritize the invasion pathways that pose the greatest threat.
*** FYI You can access the paper and associated database here: https://www.conservationgateway.org/ConservationPractices/Marine/Pages/marineinvasives.aspx
Studies on community organization may focus on different properties, such as species richness (total number of species) or composition (a measure of the identity and abundance of spe- cies). In rocky intertidal habitats from Nova Scotia, Canada, we previously determined that richness varied across vertical (elevation) and horizontal (wave/ice exposure) gradients of environmental stress on 2 coasts of contrasting winter ice load: the Gulf of St. Lawrence coast and the open Atlantic coast. Across some limited ranges of stress, however, richness remained similar. Through multivari- ate analyses (NMDS followed by ANOSIM) of species abundance data measured for all seaweeds and benthic invertebrates, we increased our ability to detect spatial trends in community structure. The present study shows that community composition varied clearly across all studied ranges of envi- ronmental stress. Therefore, even relatively small changes in abiotic stress seem capable of altering the structure of intertidal communities. An analysis of similarity percentages (SIMPER) identified the main species that typified each environmental level and those that best discriminated between con- secutive levels across the elevation and exposure gradients. Sessile organisms (barnacles and a few brown and red seaweeds) constituted the most important characterizing species, with differences in relative importance between the 2 studied coasts. Future experimental work aiming to unravel the biotic interactions underlying the observed changes in composition across the stress gradients should benefit by initially focusing on these species.
A total of 97 species of macromolluscs were collected from 4 rocky beaches (Manora, Buleji, Nathiagali, and
Cape Monze) along the Karachi coast from December 1993 to December 1995. More species were recorded from Buleji (68) and Manora (63) than from Nathiagali (55) and Cape Monze (57). Gastropods dominated at all 4 of the sites studied. Four species were commonly abundant at all 4 sites: Turbo coronatus, Nerita albicilla, Morula granulata, and Cerithium rubus. Th e average number of species decreased with an increase in the tidal heights at Manora, Buleji, and Nathiagali, whereas this was greater in the high tidal zone at Cape Monze’s rocky shore. Th e average number of individuals of molluscs was greater in the midtidal zone at the Manora and Buleji rocky shores, whereas it was greater in the low
tidal zone at Nathiagali and Cape Monze. Two-way nested analysis of variance showed that the number of individual molluscs was significantly different among zones and among sites in most of the samples. Species richness, diversity, and evenness, however, were not found to be significantly different among zones and sites. Cluster analyses, derived from Bray-Curtis measures of similarity based on abundance data, showed the discrimination between carnivore gastropods and an increase in the abundance of herbivore gastropod molluscs. Differences in community structure amongst sites appeared to be due to habitat structure, substrate instability, human disturbances, and degree of exposure.
This paper reports the results of preliminary research evaluating the potential of farming
Megabalanus azoricus. From March 2006 to September 2006, artificial substrates were
immersed bi-monthly in a shallow water bank located in the channel separating the islands
of Faial and Pico, Azores. They were monitored monthly for a period of 12 months by
scuba-diving. M. azoricus rapidly colonised the immersed substrates, establishing itself as
the dominant organism. Even though recruitment was observed year round, there was a
peak in recruitment between June and October. The substrate immersed for the longest period (15 months) presented final densities of 1109 ind. m
-2
, from which 20.2% were of edible size. Growth was monitored for 18 isolated barnacles for 8 months. Growth rate proved
to be high (base diameter; 0.08 ± 0.02 mm day
-1
; mean ± SD), with individuals reaching diameters of 21.35 ± 6.2 mm after 8 months. Considering this growth rate, it was estimated
that after a further 9 months, over 80% of the total densities (on the oldest substrate ) would
be harvestable, thus suggesting a production cycle of 17 to 24 months. Although much further research is needed, the species presents all characteristics of a potential candidate to
initiate the aquaculture industry in the Azores.
Variation in the level of settlement and recruitment in the intertidal barnacle Semibalanus balanoides was studied using a hierarchical sampling programme. The effect of three spatial scales, 10s of metres (sites), 1000s of metres (shores) and 100s of kilometres (locations), was determined. The largest spatial scale represented the distance between four widely separated locations, Sweden, the Isle of Man, SW Ireland and SW England, covering a. large part of the range of S. balanoides in Europe. Temporal variation was determined by comparison between two years, 1997 and 1998. The settlement period of S. balanoides varied in length and timing, being earlier and shorter at the most northerly location, Sweden. The duration of settlement showed little difference among shores within locations, but the pattern of settlement did vary. Estimates of total settlement throughout the settlement period and of recruitment at the end of this period both showed substantial variation among locations which was dependent on the year of study. There was little consistency in the ranking of locations between the two years. Recruitment showed significant variation I the lower spatial scales of shore and site. In addition, examination of variance components showed a high degree of variation between replicates within sites in 1997. There was a significant relationship between settlement and recruitment at three of the four locations. Across all locations variation in settlement explained between 29 and 99% of variation in recruitment. However, locations showed distinct differences in the level of post-settlement survival. (C) 2000 Elsevier Science B.V. All rights reserved.
The distribution, abundance and recruitment of Chthamalus species were studied for one year at two rocky shores on the central coast of Portugal. Chthamalus montagui is the most abundant intertidal barnacle on the Portuguese mainland. Higher abundance of C. montagui was found on the lower levels of the more sheltered shore, which is closer to the in£uence of the Tagus estuary. Chthamalus stellatus was also present, in very low densities, and always con¢ned to the lower level of the barnacle zone. Chthamalus stellatus was more common at the shore farther away from the estuary, in which exposure to wave action is higher. The meta-morphs of C. stellatus settled at the studied shores are considered to be immigrants from other populations, where the density of adults is su¤cient for cross-fertilization to occur. Chthamalus spp. recruited almost continuously throughout the year, with a peak between July and September and a gap during February and March. Variations in phytoplanktonic assemblages and temperature may be the main factors control-ling the reproductive season of Chthamalus spp. Recruitment was usually stronger on the lower shore levels but extended for a longer period higher on the shore. Seasonal variations of C. montagui abundance were greater on the lower levels of the more exposed shore. This is probably due to faster growth and higher mortality of barnacle populations occupying the lower shore levels at the more exposed habitats.
Spatial variability in the population dynamics of the intertidal acorn barnacle Semibalanus balanoides was investigated using a hierarchical sampling programme. Variability in a number of population parameters (size distribution, density, % cover, absolute growth and instantaneous mortality) was determined separately for new recruits and adults over 3 spatial scales. Three locations, SW Ireland, the Isle of Man and the west coast of Sweden, which cover a large part of the European range of this species, were selected to investigate variability over a large spatial scale (100s of kilometres). Two smaller scales, shore (1000s of metres) and site (10s of metres) nested within each location were also used. In addition, temporal variation over two 6 mo periods was also examined in the Isle of Man and Ireland. Most variability for all population parameters occurred over the largest spatial scale (location). This was a direct result of differences between Sweden and the other 2 locations, the Isle of Man and Ireland, which showed highly similar levels of all population parameters. The population of S, balanoides at the Swedish location was characterised by high growth rates, large size, high levels of mortality and a large turnover of bare space. At the spatial scale `shore', only 1 population parameter, the growth rate of recruits, showed variability. At the smallest scale of `site', all parameters showed significant variability except growth rate of adults. Calculation of variance components showed that differences between replicates (spatial scale: <0.5 m) accounted for little of the overall variability, in general less than the scales of site and shore. Examination of temporal variability over two 6 mo periods revealed no difference between time periods and no significant interaction between temporal and spatial scales, Thus, there was consistency of spatial variability over time. The potential causes of variability in population parameters of S, balanoides at different spatial scales and the implications for future studies are discussed.
A demographic model for an open population with space-limited recruitment has been previously proposed and tested using the barnacle Balanus glandula on a single shore in California. The model makes a number of qualitative predictions about population structure. At small scales, areas of high settlement should have on average less free space and fewer cohorts. At a larger unspecified scale (>34.6 cm(2)) cohort structure should be more variable in areas of high settlement. We attempted to test these qualitative predictions on a number of different spatial scales using the barnacle Semibalanus balanoides. A recruitment gradient was defined for S. balanoides around the coast of Anglesey, Wales, with the north having lower recruitment than the south regardless of year. Given this recruitment gradient, a nested ANOVA was used to examine the qualitative predictions of the demographic model at different scales. The qualitative predictions of the demographic model were not generally supported by an analysis of data from Anglesey. Free space and small-scale population variance did not vary between areas of different recruitment density. Barnacle size variation was greater on high recruitment shores at an intermediate scale (100 m) as predicted by the model. However, this difference was not statistically significant. Even at the scale of individual 5 x 5 cm photographs there was no evidence of a positive relationship between barnacle size variance and free space. Possible reasons for the mismatch of the demographic model predictions and empirical observations are discussed. There may be insufficient spatial sampling, insufficient recruitment difference, large-scale variation in mortality and growth rates, or the model assumptions may be incorrect. One important difference between the 2 levels of recruitment is that low recruitment sites had a constant patch size below 25 cm(2), whereas the high recruitment sites did not. If patch scale is variable, the predictions of the demographic model will be irrelevant as there is no single scale at which they can be observed. Use of the nested ANOVA technique with logarithmic spatial scales also allows hypotheses to be made about the important spatial scales for future demographic studies using manipulative experiments. For population variance, free space and opercular length the important scales were small (<1 m), meso- (100 m), and large scales (>10 km).
There are approximately a dozen species of commercially interesting barnacles worldwide, some of which have been cultured on a semi-industrial scale. These species are listed and information is provided with regard to geographical distribution, landings and prices. Traditionally, ‘goose’ barnacles (four species) are considered to be the most important for consumption. World production already stands at 500 tonnes year−1, but this species has not been cultured to date. Some ‘acorn’ barnacles are also consumed (seven species), with harvest levels per species that do not exceed 200 tonnes year−1 and selling prices that can reach US$17/kg. ‘Acorn’ barnacle culture on a world scale is still developing. Nevertheless, production has occurred on a semi-industrial scale; specifically, spat have been collected from the wild and grown in suspended systems. Farming trials have focused on two species of acorn barnacles: Austromegabalanus psittacus (Molina 1782) ‘picoroco’ in Chile and Megabalanus azoricus (Pilsbry 1916) ‘craca’ in Portugal. The large-scale production of these crustaceans will depend on the optimization of spat collection from the wild and/or the parallel development of mass production technologies for larvae (hatcheries). In addition, further development will be achieved by opening up new markets for commercialization.
Tetraclita squamosa and Tetraclita japonica are common, intertidal barnacles. In Hong Kong, the population dynamics of the two species exhibited spatial and temporal variation on two semi-exposed shores. T. squamosa produced egg masses from May–June and annual settlement and recruitment occurred from June–July. In contrast, settlement and recruitment of T. japonica was sparse from March–May, but intensified in July–October. Mature gonads and egg masses were, however, only present from September–November, suggesting the larvae from the two settlement pulses originated from other locations as well as Hong Kong populations. Settlement intensity and post-recruitment mortality of the two species varied between sites, possibly due to spatial variation in free rock space, physical transport of larvae and abundance of food in the water column.
Balanus amphitrite, an acorn barnacle, is distinctly euryhaline, eurythermal and a dominant fouling organism found in warm and temperate waters throughout the world. In this study, the influence of temperature and food concentration on the reproductive biology of this species collected from a tropical habitat was evaluated. Adult barnacles were maintained at 20, 25 and 30°C temperatures at different concentrations of food (50, 100, 150 and 200 Artemia ind−1day−1). In this previously believed obligatory cross-fertilizing hermaphrodite, self-fertilization was observed. The rise in temperature from 20 to 30°C resulted in a longer interbreeding interval (6–7days, 200 Artemia ind−1day−1; 11–13days, 50 Artemia ind−1day−1). Computed carbon gained through feeding during the interbreeding interval indicated an inverse relationship to the temperature. At 20°C, although a greater amount of carbon was gained through feeding, the numbers of larvae produced were fivefold less when compared to those raised at 30°C. At 20°C, 2.3μg C was required to produce a single larva, whereas at 30°C it was 0.4μg C. A rise in rearing temperature also influenced the molting rate positively. Observations on temporal variation in the gonad development of this species in a tropical coastal environment influenced by the monsoons indicated gonad development to be positively related to chlorophyll a concentration.
The present work addresses the effect of environmental factors (icing, water temperature, food availability) on the ecology of the patellid limpet Nacella (Patinigera) concinna, in a bay on the Antarctic Peninsula. Sampling was conducted at three depths (intertidal, 5m, 10m) from February 1987 to January 1988. Temperature was recorded and concentrations of Chlorophyll a were measured on the bottom, in the water and in the ice-water layer. The limpets were measured, weighed and a condition coefficient for somatic and gonadal mass was calculated. Their ages were estimated through size frequency distribution analysis and a seasonalized von Bertalanffy growth model was applied. The intertidal subpopulation migrated to deeper levels at the beginning of the icing season and recolonized the intertidal zone after ice retreat. The growth rate was very low (von Bertalanffy K 0.08). Growth rates showed important seasonal variations, with maxima during December and January. Nacella (P.) concinna spawns once a year and spawning coincided with raising water temperature (from -1.33C to-0.84C), and probably was also related to increasing spring food availability. Body mass increased during periods of high standing stock of microphytobenthos, revealing that ice-algae and phytoplankton were of minor importance as food sources for limpets in Esperanza Bay.
The golden mussel, Limnoperna fortunei, is an invasive freshwater bivalve. Since its introduction to Argentina, it had caused damage to the native fauna as well as economic damage to industries of the region. Here, we describe the growth of L. fortunei in a natural temperate environment in Argentina. Age was estimated according to the modal progression method. The constants in the von Bertalanffy growth model were adjusted by an iterative algorithm. Three annual cohorts had similar growth rates. The estimated t
0 for each cohort showed a temporary displacement in relation to the spawning period.
The size of bottom-up subsidies, food and larvae, from the ocean has a profound impact on inter-tidal communities and populations. Alongshore variations in subsidies are attributed to variation in coastal conditions, but also might be due to variations in surf-zone hydrodynamics. We tested this hypothesis by comparing surf-zone phytoplankton concentrations to surf-zone hydrodynamics as indicated by the width of the surf zones. To minimize the potential effects of alongshore variation in phytoplankton abundance in the coastal ocean, we sampled closely spaced sites (median separation 1 km) over short periods (3 days). Surf-zone concentrations of coastal phytoplankton taxa (e.g. Chaetoceros spp., Pseudo-nitzschia spp. and dinoflagellates) varied with surf-zone width; 65% to 94% of the variability in their concentration is explained by surf-zone width. Where surf zones were narrow and more reflective, phytoplankton concentrations were one to several orders of magnitude lower than in wider, more dissipative surf zones. The most closely spaced stations were 30 m apart, but represented distinct habitats – a reflective and a more dissipative surf zone. Phytoplankton concentrations in the reflective surf zone were an order of magnitude or more lower than in the adjacent more dissipative surf zone. A reanalysis of a published study on phytoplankton subsidies found similar results. Alongshore variation in surf-zone hydrodynamics appears to be an important driver of phytoplankton subsidies to the inter-tidal zone.
Population dynamics of the Balanus improvises (Crustacean: Cirripedia) was studied in three stations Amirabad, Khazarabad in the eastern part and Noor in the central part of the Southern Coasts of the Caspian Sea. Sampling procedure was carried out monthly from July 2007 to July 2008. In this study longitudinal diameter aperture (orifice or opercula diameter) of 4118 individuals as well as dry weight and ash free dry weight of 141 barnacles were measured. Barnacle population density decreased in all three stations during autumn and winter. Barnacle density in Khazarabad was significantly higher than the other two stations (p > 0/05). In this study, for dry weight and ash free dry weight maximum 247 and 122 mg and minimum 0/5 and 0/25 mg were obtained respectively. Emergence of a young cohort in March 2008, indicates the reproduction season and larval recruitment at this time. Also the frequency of the larval recruitment from April 2004 until mid-summer had increased. Opercula diameter of B. improvisus correlated with dry weight (R²= 0/87, n = 115) and ash free dry weight (R²= 0/77, n = 115). In addition, two equations for correlation of opercula diameter with dry weight (W = 0/49 L2/6, Re = 14) and ash free dry weight (W = 0/16 L2/81, Re = 18/8) for this species were calculated.
The seasonal variation in biomasses (total number, total weight, tissue weight and dry tissue weight) of intertidal macro-organisms of the rocky shore of Buleji was studied during the period August, 1993 to July, 1994. Collections were made from the low, mid and high-tide zones. Buleji rocky ledge supports abundant and diverse fauna consisting mainly of gastropods, crustaceans, echinoderms, polychaetes, fish, sponges and ascidians. Gastropods are the major contributors to biomass. Cerithium morus, Tiara tuberculata, hermit crabs, Cerithium sp., Turbo coronatus, Cerithium carbonarium, amphipods, isopods and Planaxis sulcatus were the most abundant species found at Buleji and in that order. The total number of animals was highest (29395) in the mid-tide zone and lowest (5757) in the low-tide zone. Similarly the highest and the lowest total weight (animal + shell) was recorded from the mid and the low-tide zones, respectively. Wet and dry tissue weights were highest in the month of January. In August and June the highest (0.45) species diversity (Shannon-Weiner Index) and Evenness Index (0.94) were computed.
1. A method of producing a pre-arranged pattern and density of barnacle settlement is described, which makes use of the tendency for barnacle cyprids to settle in small pits. The pits had a negligible influence on growth-rate after the first 2 weeks. This method was used to study the influence of water flow, population density and orientation on the rate of growth of B. balanoides in the Menai Straits, North Wales. 2. Barnacles parasitized by Hemioniscus balani grew more slowly than unparasitized individuals. 3. The passage of an uninterrupted current of water over the barnacles was the most important factor in promoting rapid growth. 4. Population density appreciably influenced growth in volume only when the individuals were closely packed, either touching or nearly touching. Even at densities as high as 4 individuals per cm2, much of the loss in cross-sectional area caused by space limitation was compensated for by increase in height. The effect of close packing in itself did not appear to be harmful. 5. In a unidirectional current, there was little evidence that the leading individuals in a group grew appreciably faster than the trailing ones. 6. Orientation with the rostrum pointing to the current source conferred an advantage resulting in slightly enhanced growth. 7. It is shown that a barnacle whose growth is isometric and determined only by the rate of intake of food from a current of constant nutrient content would grow at a constant linear rate. This is approximately true for the greater part of the growth curve of the species investigated. Early growth just after metamorphosis is slower, probably because the rate of water flow is reduced in the immediate vicinity of the solid substratum. Growth slows down after maturity in all species as a consequence of metabolic changes.
1. The reproductive cycles and brood production of Chthamalus fissus, Balanus glandula and Tetraclita squamosa from central California are compared. C. fissus produces about 16 small broods from March through October. B. glandula produces three to six relatively large broods from December or January to May. T. squamosa incubates only about three intermediate-sized broods from June through September.2. Brooding in C. fissus is regulated by food availability, and yolk for no more than one brood is stored at a time. Feeding in the laboratory elicited high brooding frequencies during periods when brooding activity and food levels in the field were low, and the frequency of brooding was directly proportional to the size of the food dosage. Temperature and photoperiod did not affect brooding frequencies. B. glandula rapidly stores nutrients in the ovary for about three broods during summer. Cold temperatures induce early brooding in the laboratory during late fall and early winter, and the population in the war...
The yellow clam, Mesodesma mactroides, is an intertidal bivalve typical from sandy beaches of the South American Atlantic coast. Growth parameters of southernmost
populations of M. mactroides were studied and compared with other populations. Thin shell sections were examined to describe internal shell layers and to contrast with external shell transparency. Periodicity of deposition of external growth increments was studied recording the degree of transparency of the shell border. Growth patterns were determined using modal progression analysis from size frequency distributions, analysis of external shell increments, and size-at-age data derived from inner shell layers. Growth parameters were described using the von Bertalanffy growth model. Both internal and external patterns were coincident and exhibited a succession of one translucent and one opaque region. The transparent region was deposited during summer. Growth differences found between
populations may be related to unequal size of first ring in both beaches. This feature may
originate from asynchrony in spawning and recruitment. The monthly analysis of shell
length size frequency distribution shows that growth of M. mactroides is seasonal.
Estimations of asymptotic size of studied populations and others located at the southern
(coldest) half of the geographical range of distribution suggest a negative relation with
latitude.
Marked seasonality of ship-observed chlorophyll concentrations in the upper layers of the central and northern parts of the Arabian Sea is established for three hydrographically defined offshore areas. A peak related to the southwest (summer) monsoon occurs, either with or without a northeast (winter) monsoon-related peak. Both appear to depend on the establishment of a deep mixed layer and the concomitant nutrient supply, but at any station the relation between pigment content and mixed-layer depth or nitrate concentration is usually obscure.
The reproductive cycles of two intertidal barnacles, Chthamalus stellatus (Poli) and C. montagui Southward, were studied at Lough Hyne Marine Reserve, Cork, Ireland, over 28 months. In both species there were seasonal trends in development of the male and female reproductive organs with, for example, the ovaries regenerating while eggs were being brooded. Breeding occurred mainly during June–August but also at other times. The sizes of the ova and eggs of the two species were compared and the timing of the cycles relative to other areas considered.
Adult Tesseropora rosea (Krauss) and Tetraclitella purpurascens (Wood) are mostly found in the eulittoral (barnacle) zone of rocky seashores in New South Wales. Below this zone most space is occupied by the tube-worm Galeolaria caespitosa (Lamarck) or by various species of macroalgae. Within the eulittoral zone, T. rosea are mostly on sunny areas of rock exposed to relatively strong wave-action. T. purpurascens are present mainly in crevices, caves, and under ledges where there is considerable shade.Cyprids of both species settled on sandstone plates and on experimentally cleared areas in the barnacle and Galeolaria zones. Neither species settled where the substratum was already covered by algae or Galeolaria. No spat of T. purpurascens were found in sunny areas of the barnacle zone. T. rosea, however, settled in cleared substrata in sunny and shaded areas. Neither species settled in the littoral fringe above the upper limit of distribution of adults. On boulders transferred to high levels of the shore during a storm, small T. purpurascens died within a few weeks.Barnacles of both species which had settled in experimentally cleared areas in the Galeolaria zone survived and grew. In these areas some T. purpurascens were killed by being smothered by tube-worms which settled after the barnacles. This probably happens to T. rosea, but was not demonstrated experimentally. In the Galeolaria zone, both species of barnacles were very quickly smothered and killed by macroalgae growing over them, except where these were experimentally removed.Within the barnacle zone, all newly-settled spat of T. purpurascens transferred to sunny sites died within two months, whilst many of those in shaded sites survived. In areas where wave-action was strong, spat of T. rosea survived and grew well in sunny areas, but survived better in the shade. Under a ledge, however, where wave-action was reduced, all the T. rosea in sunny sites, and most of those in shaded sites died within two months; many newly-settled T. purpurascens survived in the shade in this area.The grazing limpet Cellana tramoserica (Sowerby) dislodged and crushed some newly-settled T. rosea and reduced survival in some sunny areas. T. rosea settled preferentially on bare rock and were rarely found on the shells of adult barnacles. Thus, the density of spat was greater where adult barnacles were absent. In contrast, many newly-settled T. purpurascens were found on the shells of adults of their own species in shaded areas; they also settled on cleared rock. Because T. purpurascens tended to settle amongst and on adults, and in crevices and confined areas, they were not much affected by limpets. When newly-settled T. purpurascens were in high densities, they had lower survival than in areas with reduced densities, because of squashing and smothering by each other.The upper and lower limits of vertical distribution (zonation) of these two species of barnacles are determined primarily by the settlement of cyprids. Neither species settled at the highest levels on the shore. Whether this was due to the decreasing time of submersion during high tide towards the top of the shore, or a result of preferences for settlement site is unknown. Even if cyprids were to settle in the littoral fringe, the spat would die very quickly probably as a result of desiccation. Below the barnacle zone, the entire substratum is usually occupied by other sessile species, particularly macroalgae, on which the barnacles do not settle. In experimentally cleared areas below the barnacle zone, or in any naturally cleared areas both species settled, and could survive the physical conditions. Newly-settled spat were, however, overgrown and killed by algae and Galeolaria.Within the barnacle zone, T. purpurascens is restricted to shaded areas because of the inability of newly-settled spat to survive the physical stresses of high temperature and desiccation in sunny habitats. T. rosea appears to be excluded from shaded areas by a combination of the lack of suitable substrata on which to settle, and the effects of reduced water-flow in many crevices and under ledges. T. rosea survived better in areas with strong wave-action and can survive in shaded areas where water-flow is not reduced by the topography of the substratum.
[The effect of temperature on breeding activity and moulting of the tropical barnacle, Chthamalus malayensis was studied under rearing conditions in the laboratory. Both breeding activity and moulting frequency were influenced by temperature. Temperature seems to be the main external factor regulating both breeding and moulting in C. malayensis in Hong Kong. The temperature above which breeding begins in C. malayensis agrees well with the natural breeding season. L'effet de la température sur l'activité de reproduction et la mue du cirripède tropical, Chthamalus malayensis a été étudié dans des conditions d'élevage au laboratoire. L'activité reproductive et la fréquence de mue étaient influencées toutes deux par la température. La température semble être le principal facteur externe régulant à la fois la ponte et la mue chez C. malayensis à Hong Kong. La température à laquelle la reproduction commence chez C. malayensis s'accorde bien avec la saison naturelle de reproduction., The effect of temperature on breeding activity and moulting of the tropical barnacle, Chthamalus malayensis was studied under rearing conditions in the laboratory. Both breeding activity and moulting frequency were influenced by temperature. Temperature seems to be the main external factor regulating both breeding and moulting in C. malayensis in Hong Kong. The temperature above which breeding begins in C. malayensis agrees well with the natural breeding season. L'effet de la température sur l'activité de reproduction et la mue du cirripède tropical, Chthamalus malayensis a été étudié dans des conditions d'élevage au laboratoire. L'activité reproductive et la fréquence de mue étaient influencées toutes deux par la température. La température semble être le principal facteur externe régulant à la fois la ponte et la mue chez C. malayensis à Hong Kong. La température à laquelle la reproduction commence chez C. malayensis s'accorde bien avec la saison naturelle de reproduction.]
An account is given of the stomach contents of some common barnacles; these include both intertidal and sublittoral species. The contents reflect to some extent the environment, species taken from the same place at the same time having similar contents. With some species, a particle size analysis was possible on a pooled sample of stomach contents. It is evident that much debris is present, and that particulate matter with a diameter less than 2 μ can be taken. Detritus may be an important source of nutriment with sublittoral species. Small particles cannot be taken by the captorial activity of the cirri. It is considered that glandular secretions at the base of the cirri, where there are numerous setae, enmesh the food, which is then carried forward to the mouth parts to be rejected or accepted.
A new computer-based method is presented for the "tracing" of growth curves through fish length-frequency samples sequentially arranged in time. The method allows for an objective extraction of growth parameters whenever representative samples are available from a fish population. The method is suited both to the analysis of growth in tropical stocks and in temperate stocks, where it oscillates seasonally. A full program listing with user's instructions is available from the authors.
Long-term fluctuations (3-9 years) in the abundance of the barnacle Chthamalus dentatus were determined from archival photographs of permanent 0,25 m2 quadrats in the mid-littoral at 11 sites along the Transkei coast. These data were combined with a more detailed analysis of growth and recruitment over one year. Recruitment occurred in spring and autumn, but periodogram analyses revealed additional cycles with frequencies of 24-36 months. There was no geographic pattern in long-term differences in abundance between sites nor were these related to human disturbance. Recruitment intensity was significantly related to mean abundance of adults, which may indicate limited larval dispersal or gregarious settlement. Maximum aperture length increased by 3,0 mm in the first year but increased by only 1 mm·year−1 in the third year. Individual growth was variable, with small individuals often overtaking larger ones. There were few large individuals, those of 7,0 mm or more constituting only 3% of the population. An analysis of longevity indicated a mean lifespan of 1,5 + 0,5 years.
The distribution of the warm-water barnacle, Balanus
perforatus, was surveyed along the south coast of England and the north-east coast of France between 1993 and 2001, repeating work carried out between the 1940s and 1960s. The species has recovered from catastrophic mortality during the severe winter of 1962–1963 and was found over 120 km (UK) and 190 km (France) east of previous records on both sides of the Channel. The presence of the species in the eastern Channel refutes suggestions in the 1950s that larvae, and hence adults, would not be found east of the Isle of Wight because of reproductive sterility close to the limits of distribution. Brooding of specimens translocated to Bembridge, Isle of Wight, commenced in May, earlier than previously observed in British waters, and continued until September. The stage of embryo development at Bembridge in mid-August was comparable to that of the large population at Lyme Regis, Dorset 100 km further west. However the size of brood per standard body weight was greater at Lyme Regis. Factors influencing the rate of colonization and further geographic range extension of the species as a possible result of climate change, are discussed.
The barnacle Balanus glandula is predominantly an open coast species in the Northeast Pacific. However, B. glandula densely inhabits estuaries where environmental conditions such as salinity and temperature drastically differ from the open coast. The increased variability of environmental conditions within an estuary can potentially affect spatial patterns of reproduction in B. glandula. I examined gonad maturity, reproductive periodicity and fecundity, and then calculated reproductive output in B. glandula populations distributed along an estuarine gradient. Results indicated that reproductive output of this intertidal barnacle decreased four times over a spatial scale of kilometers, as a transition occurred from a marine to a freshwater habitat along an estuarine gradient. Additionally, a higher proportion of the population had well-developed gonads in the oceanic end of the estuary compared to the riverine end. These results indicate how reproductive pattern can significantly vary over a spatial scale of kilometers, resulting in site-specific contributions of offspring to the larval pool.
This study presents a historical review, a meta-analysis, and recommendations for users about weight–length relationships, condition factors and relative weight equations. The historical review traces the developments of the respective concepts. The meta-analysis explores 3929 weight–length relationships of the type W = aLb for 1773 species of fishes. It shows that 82% of the variance in a plot of log a over b can be explained by allometric versus isometric growth patterns and by different body shapes of the respective species. Across species median b = 3.03 is significantly larger than 3.0, thus indicating a tendency towards slightly positive-allometric growth (increase in relative body thickness or plumpness) in most fishes. The expected range of 2.5 < b < 3.5 is confirmed. Mean estimates of b outside this range are often based on only one or two weight–length relationships per species. However, true cases of strong allometric growth do exist and three examples are given. Within species, a plot of log a vs b can be used to detect outliers in weight–length relationships. An equation to calculate mean condition factors from weight–length relationships is given as Kmean = 100aLb−3. Relative weight Wrm = 100W/(amLbm) can be used for comparing the condition of individuals across populations, where am is the geometric mean of a and bm is the mean of b across all available weight–length relationships for a given species. Twelve recommendations for proper use and presentation of weight–length relationships, condition factors and relative weight are given.
Aim Our aim in this paper is to present the first broad‐scale quantification of species abundance for rocky intertidal communities along the Pacific coast of North America. Here we examine the community‐level marine biogeographical patterns in the context of formerly described biogeographical regions, and we evaluate the combined effects of geographical distance and environmental conditions on patterns of species similarity across this region.
Location Pacific coast of North America.
Methods Data on the percentage cover of benthic marine organisms were collected at 67 rocky intertidal sites from south‐eastern Alaska, USA, to central Baja California Sur, Mexico. Cluster analysis and non‐metric multidimensional scaling were used to evaluate the spatial patterns of species similarity among sites relative to those of previously defined biogeographical regions. Matrices of similarity in species composition among all sites were computed and analysed with respect to geographical distance and long‐term mean sea surface temperature (SST) as a measure of environmental conditions.
Results We found a high degree of spatial structure in the similarity of intertidal communities along the coast. Cluster analysis identified 13 major community structure ‘groups’. Although breaks between clusters of sites generally occurred at major biogeographical boundaries, some of the larger biogeographical regions contained several clusters of sites that did not group according to spatial position or identifiable coastal features. Additionally, there were several outliers – sites that grouped alone or with sites outside their region – for which localized features may play an important role in driving community structure. Patterns of species similarity at the large scale were highly correlated with geographical distance among sites and with SST. Importantly, we found community similarity to be highly correlated with long‐term mean SST while controlling for the effects of geographical distance.
Main conclusions These findings reveal a high degree of spatial structure in the similarity of rocky intertidal communities of the north‐east Pacific, and are generally consistent with those of previously described biogeographical regions, with some notable differences. Breaks in similarity among clusters are generally coincident with known biogeographical and oceanographic discontinuities. The strong correlations between species similarity and both geographical position and SST suggest that both geography and oceanographic conditions have a large influence on patterns of intertidal community structure along the Pacific coast of North America.
The effect of geographical differences in breeding cycles on the recruitment variation of the limpets — Patella vulgata L., P. aspera Rding and (to a limited extent) P. depressa Pennant — has been studied over much of their range in Britain and NW. Europe. In spite of considerable annual and local variation in recruitment success, broader patterns can be distinguished, which can be linked to spawning times and factors affecting the survival of newly-settled spat. The breeding cycles of P. vulgata and P. aspera differ across their ranges in that, in both species, spawning begins, and gametogenesis ends, earlier in the north and east than in the south and west. The cause of these differences can be correlated with geographical and annual differences in sea temperature over the potential breeding periods, and can be related to the regional incidence of conditions found experimentally to be necessary for successful settlement and survival of spat during a critical stage of their growth. The significance of this temperature window in determining the littoral and geographical distribution of the species is discussed.