Settlement Mark Research Articles

Experimental Research of Excavation Disturbance Effect Due to Trenchless Construction by Using Distributed Strain Sensing Technique

In this paper, an assessment method of excavation disturbance effect is proposed by using distributed optical-fiber strain sensing technique. Model tests of trenchless construction under different parameter conditions are carried out in the laboratory. In the test, the excavation was simulated by using the deflate of pre-burying air bag, soil displacement is measured by settlement mark, at the same time, The soil strain of overburden layer is obtained based on Brillouin Optical Time-Domain Analysis (BOTDA). Through the analysis of the experimental data, the partition theory of excavation disturbance zone is proved and verified through test data. The correlation between ground settlement and soil strain distribution due to trenchless construction are compared and analyzed. The mechanical response of overlying pavement are further discussed. Research results indicate that soil strain of overburden layer is symmetrically distributed about the excavation surface, which is compressed near the centerline and tensioned on both sides due to the excavation disturbance impact. The width of excavation disturbance zone derived from the test data shows good accordance with the calculation results based on the partition theory, the maximum error is less than 10%. A certain consistency exists between the distribution law of strain curve and settlement trough. Due to the uneven distribution of support force caused by foundation settlement, the pavement model shows notable bending deflection after trenchless excavation, and the maximum increment ratio of support force exceed 50%. The combined impact of ground traffic load and excavation disturbance is considered to be more unfavorable to the safety of pavement structure. The conclusions can be suggestive and helpful to trenchless excavation control.

Planktonic larval duration, early growth, and the influence of dietary input on the otolith microstructure of Scolopsis bilineatus (Nemipteridae)

The pelagic larval phase represents a critical period in the early life history of fishes, since larval growth and development can contribute substantially to patterns of survival, dispersal and connectivity. The microstructure of otoliths was examined to investigate events during the early life history of the bridled monocle bream Scolopsis bilineatus (Nemipteridae) on the Great Barrier Reef. We validated a distinct settlement mark, characterized by a rapid transition from wide to narrow increments. The time fish spent in the plankton (Pelagic Larval Duration; PLD) ranged from 17 to 27 days (mean = 21.3 days), which is similar to many other fish families. Three distinct early life history stages occurred: pre-settlers (larvae), newly settled fish, and settled juveniles. Increment width (a proxy for growth) was sequentially narrower with each life history stage; pre-settlers>newly settled>settled juveniles, and growth was reduced as fish approached and underwent settlement to reef habitats. Evidence is provided for a “search phase”, whereby growth was reduced in the three to four days preceding settlement; this pattern may be indicative of changes in the behaviour of larvae immediately prior to settling. Two manipulative experiments investigated the effects of diet ration on otolith increment widths. Reduced food intake resulted in significantly narrower increment widths, with a possible lag effect of at least six days. Experiment results indicated that increment widths can be a reliable proxy of somatic growth, and results from this study overall highlight the utility of otoliths as a tool for investigating the early life history of fishes.

“Sacred Ties of Brotherhood”

Katherine Magyarody, “‘Sacred Ties of Brotherhood’: The Social Mediation of Imperial Ideology in The Last of the Mohicans and Canadian Crusoes” (pp. 315–342) This essay analyzes narrative patterns of colonist-indigenous relations within Daniel Defoe’s Robinson Crusoe (1719) and two Robinsonade texts, James Fenimore Cooper’s The Last of the Mohicans (1826) and Catharine Parr Traill’s Canadian Crusoes (1852). Within the latter texts, the multiplication of Crusoe into “castaway” groups allows for an investigation of the social collateral of reaffirming racial hierarchies via settlers’ allegiance to indigenous individuals while destroying larger indigenous communities. In The Last of the Mohicans, the hybrid Cora Munroe and the Mohican Uncas’s love for her threatens the established pattern of homosocial interracial friendship; their deaths reaffirm racial boundaries. Conversely, by depicting a “coterie” of Scotch, French-Canadian, hybrid, and Mohawk members, Canadian Crusoes self-consciously rewrites the tragedy of Cooper’s novel so that sororal love enables cross-cultural marriage. Nevertheless, Traill’s proleptic descriptions of Canadian settlement mark her narrative as an alternate history that diverges from the progressive alienation of Native communities.

Near-reef elemental signals in the otoliths of settling Pomacentrus amboinensis (Pomacentridae)

Settlement is a key life history transition for coral reef fishes, and how long a fish spends close to a reef prior to settlement is poorly understood. We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and otolith microstructure analysis (daily increments and settlement marks) to determine the length of time larval fish spend near a reef prior to settlement. The otoliths of Pomacentrus amboinensis collected from four neighbouring reefs in the southern Great Barrier Reef showed clear and consistent differences in their elemental signatures prior to and following settlement. Elevated Ba:Ca near settlement and post-settlement was found in fish from all four reefs. However, there was individual variation in elemental profiles, with an increased otolith Ba-to-Ca ratio (near-reef signature) at settlement in 33 % of fish, and up to 8 d prior to settlement in others. Increment widths, often used as a proxy for growth, decreased approaching the settlement mark for all fish, providing further evidence for a “search phase” in larvae. We demonstrated experimentally that otoliths of fish kept in reefal or inter-reefal waters had different elemental chemistry. There were differences in the elemental composition of water samples within the study area, but no consistent trends with distance from reefs. There was poor discrimination of multi-element signatures among fish from different reefs during their pre-settlement phases. However, discrimination improved in the settlement and post-settlement phases of otoliths, indicating that reef waters and perhaps stage of ontogeny affected otolith chemistry. This study demonstrated clear near-reef elemental signatures in fish around settlement. We suggest these differences are due to a combination of water chemistry and physiological influences (e.g., growth). Combining LA-ICP-MS with otolith microstructure analysis can provide high-resolution information on the early life history of reef fishes. Further, a near-reef “search phase” prior to settlement may be common in reef fishes.

A Coral-reef Fish with Large, Fast, Conspicuous Larvae and Small, Cryptic Adults (Teleostei: Apogonidae)

Settlement-stage larvae of the widespread apogonid Gymnapogon urospilotus are described and illustrated from specimens captured with crest nets at Moorea, Society Islands. Identification was confirmed by COI mitochondrial DNA analysis. Otoliths of the larvae had no settlement mark, indicating they had not previously settled, and 33–40 presumed daily rings. The larvae are transparent with large orange/red blotches on the tail, and limited melanophores on head and pelvic fins. The larvae have very long pelvic-fin rays (40–50% standard length [SL]) with black tips and contrasting white bands, and limited inter-ray membranes. They are apparently unique among teleost fishes in having a strongly serrate urohyal. These serrations disappear after settlement. Critical speed of the larvae was measured in a swimming chamber. Larvae of G. urospilotus are the largest (19–24 mm SL), oldest (33–40 days), and fastest (>36 cm s−1) known apogonids at settlement. Photos of larvae of G. urospilotus from Guam, Ryukyu Islands, and Indonesia reveal they swim 2–3 m above coral reefs at night with the pelvic rays spread wide, presumably looking for settlement habitat. They are very conspicuous and may be mimicking small lionfish. In contrast, adults have never been seen alive on the reef. The largest reported adult G. urospilotus is 37 mm SL, which implies that this species undergoes a major portion of its growth as a pelagic larva, a life history pattern that also occurs in some reef gobiids.

Coping with connectivity between populations of Merluccius merluccius: An elusive topic

The elemental composition of European hake otoliths was analyzed at the core, settlement mark and otolith edge zones corresponding to the periods of pelagic early life stage, settlement to the bottom, and juvenile life, respectively. Barium, Sr, Mg, Mn and Ca were measured using LA-ICPMS on the sagitta otoliths of hake sampled in 6 different Western Mediterranean areas, separated by tens to hundreds of kilometers. The otolith edge, which should have incorporated the water mass signal of the sampling area, showed a high degree of overlap between geographical areas. This precluded the discrimination of geographically distinct groups. However, there was a clear ontogenetic signal in all the fish, with higher Sr:Ca in the otolith core. Ba:Ca was higher at the settlement mark, while Mn:Ca was overlapped with the core values. The otolith edge had lower ratios for all elements except for Mg. The conflicting effects of the ontogenic patterns and the inconclusive allocation of a geographical signal at the edge, precluded to assign individual hake to a natal origin based on the composition of the core and settlement mark zones. Our results may be explained by high mobility of the juvenile hake in this area of the Mediterranean, or by the relative homogeneity in the water masses for the four elements considered in this study. While this subset is useful for distinguishing major water masses or regional differences between, for example, the Atlantic and the Mediterranean, a larger set of elements could be needed for smaller-scale studies.

Planktonic Larval Duration, age and growth of Ostorhinchus doederleini (Pisces: Apogonidae) on the southern Great Barrier Reef, Australia

Cardinalfishes (Apogonidae) are abundant on corals reefs, but there are few data on demography to understand trophodynamics and population dynamics. Ostorhinchus doederleini is a small and abundant apogonid on the Great Barrier Reef (GBR) and throughout the western Pacific Ocean. We present key demographic parameters for the entire life history from the southern GBR. Daily deposition of increments in otoliths was validated. Fish had a Planktonic Larval Duration (PLD) of 16–26 days. PLD was established from fish collected immediately prior to settlement as no settlement mark was found. Fish grew at about 0.35 mm day−1 for the first 20 days after settlement. Fish reached a maximum standard length at about 200 days, and no fish lived longer than 368 days at four reefs separated by kilometers to tens of kilometers. There was no evidence for differences in size at age between sexes. Mortality was very high, and for fish greater than 60 days old, mortality rates ranged from 2.9 to 4.6 % day−1. Short lives and high mortality rates make O. doederleini, and potentially other apogonids, vulnerable to recruitment failure. Here, we review data on the demographic characteristics of other reef fishes. Although some taxa live to over 50 years, the short lives of apogonids are most aligned with the Gobiidae and Blenniidae (i.e., typically <1.5 years). Descriptions of fish size, age, longevity, growth and mortality, from hatching to age maxima, are very rare for most taxa, even at the level of family.

Planktonic Larval Duration, Settlement, and Growth Rates of the Young-of-the-Year of Two Sand Basses (Paralabrax nebulifer and P. maculatofasciatus: fam. Serranidae) from Southern California

Accurate estimates of Planktonic Larval Duration (PLD) have become critical to the modeling of larval dispersal and connectivity among ecological communities. Among those species where little information on larval duration is known are the spotted (Paralabrax maculatofasciatus) and barred (P. nebulifer) sand basses, two economically important species that have historically been the focus of marine recreational fisheries off southern California. PLD was determined by a count of the daily growth rings from the otolith core to the settlement check and age from the core to the otolith margin. Size at settlement was estimated by the size of the otolith from its core to the settlement mark based on the otolith size to body size relationship. Based on these significant relationships, mean size at settlement of our specimens was calculated to be 10.2 ± 1.6 mmSL for spotted sand bass and 9.1 ± 1.1 mmSL for barred sand bass. Mean PLD was 32.8 ± 2.2 days with a range from 28 to 37 days for spotted sand bass and 25.8 ± 2.2 days (range 21–30) for barred sand bass. Growth rates for the YOY of each species estimated by calculating the length-to-age relationships were 1.13 mm/day for spotted sand bass and 1.28 mm/day for barred sand bass. PLDs of approximately one lunar month and growth rates of about 1 mm/d seem to be common in those summer spawning fishes from San Diegan Province (warm temperate).

Pelagic larval duration and population connectivity in New Zealand triplefin fishes (Tripterygiidae)

The relationship between pelagic larval duration (PLD) and population connectivity in marine fishes has been controversial, but most studies to date have focused on tropical taxa. Here, we examine PLD in 11 species of triplefin fishes from a temperate environment in the Hauraki Gulf, New Zealand, to describe daily increment patterns and settlement marks in the otoliths. The formation of daily increments was validated using larvae of known age and tetracycline marking of settled juveniles. Settlement mark identity was verified by comparing total increment counts from otoliths of recently settled fishes with PLD counts from post-settlement fishes. A similar pattern of three groups of increments across the otolith was found in all specimens examined. The settlement mark was similar in all species and occurred as a sharp drop in increment width within the area of transition in optical density. PLD was lengthy, compared to species of triplefins from elsewhere, and ranged between 54.4 ± 1.7 SE days in Bellapiscis lesleyae to 86.4 ± 2.6 SE days in Forsterygion malcolmi. Variation in PLD within species was high but did not mask interspecific differences. PLD was not phylogenetically constrained, as sister species differed significantly in PLD. PLD was compared with genetic population connectivity for eight of the study species using mitochondrial gene flow data from Hickey, Lavery, Hannan, Baker, Clements. Mol Ecol 18:680–696 (2009). The observed lack of correlation between PLD and gene flow suggests that dispersal is limited by other factors, such as larval behaviour and the availability of settlement habitat.

Otolith development and daily increment formation in laboratory-reared larval and juvenile black-spot tuskfish Choerodon schoenleinii

Microstructures of lapilli were examined for reared larvae and juveniles of black-spot tuskfish Choerodon schoenleinii. Lapilli of larvae at 1 day after hatching have one diffuse and obscure ring with an otolith radius of 4.3 ± 0.50 μm (mean ± SD, N = 8). The slope and intercept of the regression between the number of days after hatching and increment counts did not differ significantly from one and zero, respectively, indicating that lapillus increments were formed on a daily basis after hatching. There was an ontogenetic shift in the relative values of somatic and otolith growth, which corresponded to the transition from pelagic larvae to settlement stage. Simultaneously, the daily increment width reached the maximum value. These findings suggest that age at maximum value of increment width can be used as an indicator of the planktonic larval duration while settlement mark is not found. Since ontogenetic shift in the relationship between otolith radius and body size was observed, back-calculation of somatic growth in black-spot tuskfish using the otolith radius during the early life stages should be analyzed with caution, and the method requires further validation.

Otolith barium profiles verify the timing of settlement in a coral reef fish

Otolith microstructure has been shown to record valuable information about fishes including age, growth, and the timing of life history transitions, while microchemical analysis can reveal information about environmental history, dispersal, and migration. For the bluehead wrasse Thalassoma bifasciatum, a common coral reef fish on an oceanic island, we examined whether otolith chemistry could be used to identify the timing of settlement from the pelagic larval phase to the reefbased juvenile phase. This species has a distinct settlement mark visible in its otolith microstructure. Using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), we found that Ba:Ca ratios increased abruptly at the time of settlement. On average, Ba:Ca ratios were 6.5× greater in the juvenile than the larval phase. Other elements (Mg, Mn, and Sr) also displayed ontogenetic changes in concentration; however, those changes were not associated with the settlement mark. We demonstrate the potential utility of otolith chemistry as a method to identify the timing of settlement (and thereby the larval duration) in other marine fishes with similar early life histories, whose otoliths may not produce distinct settlement checks or those whose settlement stage larvae may not be captured by other means.

Otolith microstructural and microchemical changes associated with settlement in the diadromous fish Galaxias maculatus

The presence of a settlement mark in the otoliths of the common galaxid Galaxias maculatus was validated by examining the relationship between changes in otolith microstructure and otolith microchemistry. Two methods were used to examine the microchemistry of otoliths: (1) laser-ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICPMS) to examine changes in Sr isotope ratios, and (2) laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICPMS) to examine changes in Ba/Ca and Sr/Ca. Both analytical techniques detected changes in otolith microchemistry consistent with movement from oceans into rivers (settlement). There was a strong correlation between the timing of settlement as indicated by otolith microstructure and both Sr-based methods; however, Ba/Ca was a less reliable marker of settlement for this species. These results support the use of this settlement mark for further otolith based studies of age, growth and the reconstruction of settlement histories in G. maculatus and demonstrate the potential utility of otolith microchemistry as a method for validating settlement marks in other diadromous fish. © Inter-Research 2008.

Dynamics in 0+ recruitment and early life history for snapper (Pagrus auratus, Sparidae) in South Australia

The population dynamics of snapper (Pagrus auratus) relate to interannual variation in 0+ recruitment. The focus of the present study was to improve our understanding of this variation for snapper in northern Spencer Gulf, South Australia. The objectives of this study were to describe the distribution and abundance of 0+ juveniles annually from 2000 to 2002 and to determine early life history characteristics through retrospective analysis of otolith microstructure from captured fish. The environmental characteristics differed between years, with 2001 being extremely hot and 2002 the coldest summer recorded. Sampling was undertaken in April after spawning and settlement were complete. The estimates of recruitment were relatively low, suggesting a complex relationship with sea surface temperature. Each year new recruits occurred at the same places that were bare and flat with muddy substratum, suggesting nursery areas are actively selected by the recruits. The sagittae from juveniles had clear daily increments and settlement mark, allowing age and presettlement duration to be determined. Growth rates varied considerably both within and between years, and were related to water temperature, which affected the presettlement duration. Based on spawn dates, successful recruitment resulted from specific periods through the reproductive season that appeared to relate to the specific water temperature regimen in each year.

Comparison of techniques of back-calculation of growth and settlement marks from the otoliths of three species ofDiplodusfrom the Mediterranean Sea

We developed a model of back-calculation of fish size from otoliths that could accommodate both changes in the relationship between otolith and somatic growth that occur through time and variation in growth rates among individuals. We used this model to back-calculate estimates of size and growth from otoliths of three species of Diplodus from the Mediterranean Sea. The outcomes of our model were compared with those of three other models and with growth curves estimated directly from populations of fish in the field. We found that our new model produced estimates of size-at-age that were closer to those observed in the field than the biological intercept, time-varying growth, and body proportional models. Comparison of profiles of increment width from otoliths of newly settled and juvenile Diplodus puntazzo and Diplodus vulgaris showed that these species formed a settlement mark, where increment width declined at settlement. In contrast, a settlement mark was not evident in the otoliths of Diplodus sargus. However, settlement of all species coincided with a sharp decline in somatic growth rate. Thus, growth rate may provide a means of estimating the timing of settlement in species that do not display a marked change in increment width.

Evaluation of periodic and aperiodic otolith structure and somatic-otolith scaling for use in retrospective life history analysis of a tropical marine goby, Bathygobius coalitus

Daily increment formation in sagittal otoliths, scaling between otolith and somatic growth, and the temporal link between settlement and formation of a settlement mark in otolith structure were evaluated for their use in reconstructing aspects of the early life history of the basalt goby Bathygobius coalitus, Formation of daily increments was validated in sagittae of fish ranging in life history stage from new recruits to sexually differentiated males and females. Total length (TL) was proportional to other measures of body length, width, and depth, and linearly proportional to sagitta radius for fish between 8 and 40 mm TL. Somatic-otolith scaling became more curvilinear in larger fish due to declining growth rate of otoliths relative to TL, especially in fish collected during warmer sea surface temperatures. For fish 8 to 40 mm TL, somatic-otolith scaling was not affected by differential somatic growth rates nor by seasonal water temperature. A settlement mark, clearly identifiable as a distinct and abrupt shift in optical focal plane, contrast, and width of daily increments, was verified to coincide with settlement. Wider post-settlement increments abruptly followed narrower pre-settlement increments across the settlement mark. These results support the use of daily increments, somatic-otolith scaling, and a settlement mark for reconstruction of hatch and settlement dates, mean daily pre- and post-settlement growth rates, size and age at settlement, and post-settlement size-at-age histories for the basalt goby.

Daily otolith increments and recruitment in two coral-reef wrasses, Thalassoma bifasciatum and Halichoeres bivittatus

Increments on the otoliths of two common coral reef fishes, the bluehead wrasse Thalassoma bifasciatum and the slippery dick Halichoeres bivittatus, were demonstrated by mark-recapture experiments to be daily. Otoliths were marked in two ways; by depriving fish of light, food, and temperature cycles and also by supplemental feeding in the field. Both experiments were performed in late 1980 in the San Blas Islands of Panama. A mark corresponding to settlement of the planktonic larva onto the reef was found on the otoliths of the bluehead wrasse. This settlement mark was used to calculate the dates of settlement of a collection of juveniles of this species taken from a patch reef in the San Blas Islands of Panama in 1981. Settlement occurred in short and irregular bursts. The number of daily increments before the settlement mark indicates a planktonic larval life of 40 to 72 d.