Counting Growth Increments Research Articles

Nondaily growth increments in the commercial species, Octopus berrima, and the importance of age validation

Abstract Age data are crucial for understanding and managing target species in commercial and recreational fisheries. Octopus catches are increasing worldwide, yet ageing methods are still in their infancy. Octopus age is estimated by counting growth increments in stylets and beaks. These increments have been validated as daily in some species or assumed to be daily in other species. Here, we conducted an age validation study on both the stylets and beaks of a commercial octopus species (Octopus berrima). Subsequently, we compared and assessed the readability of growth increments in beaks and stylets of wild-caught O. berrima. We found that increment periodicity was nondaily for both structures, with increment periodicity also varying between structures (0.75 increments per day for stylets and 0.53 increments per day for beak). This study highlights the importance of validating increment periodicity for different octopus species and for both stylets and beaks to obtain accurate age and growth data. Without accurate age data, a species may be incorrectly managed with the potential for negative effects on the sustainability of wild populations.

Estimating age and growth of roosterfish (Nematistius pectoralis) from otoliths

The roosterfish is a coastal pelagic species that inhabits shallow waters of the Eastern Pacific Ocean. Despite its ecological and economic importance within the region, there are few studies on its basic biology, especially those focused on age and individual growth. Therefore, the objective of this study was to estimate roosterfish age and individual growth parameters through counting growth increments of sagittal otoliths. The work focused on organisms caught off Baja California Sur, Mexico (BCS) by both the sport and artisanal fishing fleets from 2010–2017. A total of 266 organisms were sampled during the study period, ranging in size from 5.2–133 cm fork length. A model was generated to describe the relationship between otolith radius (OR) and fork length (FL) of the fish, where FL = -43.3 + 44.59 OR. The periodicity of otolith growth increment formation was annual, and this study found roosterfish age estimates to range from 0 to 8 years old, with most individuals ranging from 1–2 years of age. Based on the fitting of the data to three individual growth models (Gompertz, Logistic and von Bertalanffy, VBGF), the VBGF best fit the individual growth curve for roosterfish. The VBGF parameter of L∞ = 131.53, k = 0.35 y t0 = -0.23 supports previous studies and suggests that roosterfish are very fast growing in the first years of life.

Geochemical and Microstructural Signals in Giant ClamTridacna maximaRecorded Typhoon Events at Okinotori Island, Japan

AbstractTo validate the usability of the giant clam shell as a recorder of short‐term environmental changes such as typhoons, we collected a liveTridacna maximafrom Okinotori Island, Japan, on 15 June 2006. Growth increment thickness, stable isotope ratio (δ18Oshell, δ13Cshell), and the barium/calcium ratio (Ba/Ca) in theT. maximashell sample were measured and compared to Okinotori Island instrumental environmental data. In the outer layer of the shell sample, there were 365 ± 6 growth increments per year, as estimated by the δ18Oshellprofile compared with sea surface temperature. The growth increments in the specimen were formed daily, and thus, we can determine the date of the sampling points of δ18Oshell, δ13Cshelland the Ba/Ca ratio by counting growth increments. After typhoon approach, there is a decrease in increment thickness and some disturbed growth increments. The positive peaks in the shell Ba/Ca ratio and δ18Oshellcorresponded to lower sea surface temperature caused by typhoons. These results indicated that the microstructural and geochemical record inTridacna maximashells could be useful for detecting past typhoon events.

Comparison of Three Methods for Aging the Iceland Scallop Chlamys islandica

The Gilbert Bay (GB) Marine Protected Area (MPA) on the southeastern coast of Labrador was established in 2005 to protect a resident population of Atlantic cod (Gadus morhua). Commercial dredging for Iceland scallops (Chlamys islandica) in the bay was permitted to continue under MPA regulations, but was excluded from areas of cod spawning. The average size of Iceland scallops harvested in GB is smaller than in the Strait of Belle Isle approximately 150 km to the south. Local fishermen have suggested this is due to slow growth, and this prompted the present study to test the hypothesis that Iceland scallops grow more slowly in GB than in the Strait of Belle Isle. Scallop growth was parameterized as change in shell height with age. Three methods of aging individual scallops were used: interpreting external growth rings on the shell, counting growth increments on the calcareous portion of the shell hinge ligament, and counting internal shell layer growth zones. Counting ligament growth increments and internal shell layer growth zones gave similar estimates of age. In comparison, interpreting external growth rings on the shell underestimated the age of individual scallops. If the ligament method and the internal shell layer method of aging are accurate (scallops of known-age were not examined), scallops in GB require eleven years of growth to recruit to the fishery (attain a shell height of 60 mm). This is substantially longer than the 6-y period estimated using the external growth rings method of aging. Growth rate parameters of Iceland scallops in GB, the Strait of Belle, and in the Nuuk area of West Greenland were found to be similar. The relatively small shell size of scallops presently harvested in GB is not due to anomalous growth, but more likely attributable to repeated dredging of scallop beds in the past and removal of the larger individuals.

Growth of the dolphinfish Coryphaena hippurus from north-eastern Brazil with an appraisal of the efficacy of scales and otoliths for ageing.

Age and growth of the dolphinfish Coryphaena hippurus caught off north-eastern Brazil were studied by counting growth increments on scales and otoliths. A sample (n = 2338) measuring 7·7-195 cm fork length (LF ) was collected from September 2001 to February 2003. The scales (n = 69) removed from six different regions of the body were examined and those from the caudal region exhibited greater morphological regularity, symmetry and a smaller rate of regeneration. The regression between caudal scale radius (RS ) and LF displayed was linear (LF = 28·334 RS + 9·186; r(2) = 0·754). Otolith micro-increments were counted assuming daily periodicity. Ages estimated from otoliths ranged from 64 to 659 days. The von Bertalanffy growth model was fitted based on the otolith readings generating L∞ = 194·1 cm LF , k = 0·912 year(-1) and t0 = 0·081 years. Species longevity was estimated to be c. 4 years. Ninety-eight per cent of the overall sample was adult specimens well above the age of first maturity in the study area. The large variability between scale length and LF and the failure to ascertain increment deposition periodicity suggest that scales are not appropriate for ageing C. hippurus and analysis of otolith micro-increments is deemed the best structure for ageing this species in the study area.

Using information-based methods to model age and growth of the silver scabbardfish, Lepidopus caudatus, from the mid-Atlantic Ocean

The traditional species targeted by the Azorean demersal mixed hook-and-line commercial fisheries are presently facing a decline in captures, and the demand for new demersal resources is growing. The silver scabbardfish, Lepidopus caudatus, is a potential new resource to be exploited in the region; however, reports on its vulnerability and stock status are contradictory, which highlights the importance of arriving at accurate age and growth parameter estimates for this species. The 808 individuals used in the present study were acquired from commercial landings in the Azorean islands of São Miguel and Faial, collected monthly between 2004 and 2010. Ages were determined by counting growth increments in whole sagittal otoliths. Four different growth models were fitted to the data: von Bertalanffy growth function, the Gompertz model, the logistic model and the power function. Akaike's Information Criterion was used to evaluate the models and finally a multi-model inference was employed to arrive at model-averaged estimates of L∞. The von Bertalanffy function performed as well as the other candidates, although the parameter estimates for this model were usually higher than for the Gompertz and logistic models. The analysis suggests that L. caudatus is a relatively fast-growing species that could constitute a sustainable resource for commercial fisheries in the region, pending further research into the unbalanced sex ratios observed here.

Bomb-produced radiocarbon validation of growth-increment crossdating allows marine paleoclimate reconstruction

The bivalve Pacific geoduck ( Panopea generosa) has been used in the eastern North Pacific Ocean to create proxies for environmental factors such as temperature and oceanographic conditions. This type of research depends upon accurate age determination of Pacific geoducks, which historically was based on shell growth-increment counts. A recent study comparing age estimates generated by the dendrochronology (tree-ring science) procedure of crossdating to those estimated from growth-increment counts found a significant difference between the methods for geoduck older than 30 years. Compared to the traditional age determination method of counting growth increments, the crossdating method estimates a greater longevity in this species, with some individuals living in excess of 150 years. In the present study, the accuracy of each method was independently assessed using bomb-produced radiocarbon ( 14C) techniques. Specimens whose birth years were estimated to be within the era of the bomb-produced marine 14C increase and where the differences between ages estimated by the two methods were greatest were selected for 14C analysis. The difference between age estimates from traditional growth-increment counts and those from crossdating was evaluated using their respective 14C chronologies in comparisons to a reference chronology as a standard. The comparisons relied on Bayesian nonlinear models using Markov Chain Monte Carlo simulation. This method of analysis showed that with a 50% probability geoducks were aged correctly when using the crossdating method, compared to the growth increment counts which had a 50% probability of underestimating the age by 4 years. Therefore, the crossdated age estimates were found to be more accurate than increment counts. Furthermore, these results provide new confidence in using Pacific geoduck biochronologies for paleoclimate and paleoenvironmental reconstruction.

Age determination, bomb-radiocarbon validation and growth of Atlantic halibut (Hippoglossus hippoglossus) from the Northwest Atlantic

Atlantic halibut (Hippoglossus hippoglossus) is the largest and one of the most widely-ranging and commercially-valuable groundfish in the Atlantic Ocean. Although presumed to be long-lived, their age and growth has not been validated. Ages were estimated by counting growth increments from approximately 2400 thin-sectioned sagittal otoliths collected from the Scotian Shelf and southern Grand Banks off eastern Canada. The accuracy of age estimates made from otolith thin sections was validated using bomb-radiocarbon assays of 13 otolith cores whose year of formation ranged from 1949 to 1975, encompassing the timeframe of the global radiocarbon pulse. Known-age juvenile halibut from a culture facility were used to identify the approximate location of the first annulus. Growth rate for males and females was similar up to about 70 cm (~5 years), after which point male growth slowed, while female growth continued to an age of up to 38 years and a maximum observed size of 232 cm. Males grew to an observed maximum length of about 175 cm and a maximum age of 50 years. A comparison of age estimates for otoliths collected in a ‘historic’ time frame (1963 to 1974) with those from recent years (1997 to 2007) shows that growth rate has not changed appreciably between the two time periods. Small but significant growth differences were observed between the Scotian Shelf and southern Grand Banks for both sexes, while large differences in length at age were observed between halibut caught with longline compared to otter trawl due to differences in length-based gear selectivity. Age interpretations based on sectioned otoliths tended to be 10–15% different than those based on break and burn, although the age comparison was confounded by other variables and must be considered provisional. Atlantic halibut is a long-lived fish, living up to at least 50 years, an important consideration for the management of the fishery.

Age estimation obtained from analysis of octopus ( Octopus vulgaris Cuvier, 1797) beaks: Improvements and comparisons

Two methods are currently available for age estimation in octopus beaks. They have been applied to the same specimen from a sample of 30 individuals of Octopus vulgaris caught in central-eastern Atlantic waters. These techniques aim at revealing growth increments in the rostrum sagittal sections (RSS) and lateral wall surfaces (LWS) of octopus upper and lower beaks. Both methods were improved to reduce the time of sample preparation and to enhance the appearance of the increments. For each individual, two independent readings were done for upper and lower beak sections, as well as for the lateral wall surfaces. Vertical reflected light (epifluorescence) and image analysis system were shown to be useful in the observation and analysis of the sequence of increments. Precision of the ageing, increment counts obtained by both techniques, and increment widths were discussed. Using upper beak RSS led to more precise age estimates, whereas preparing LWS was quicker and simpler, and revealed a higher number of increments. Therefore, our study recommends counting growth increments in LWS of beaks to age adult common octopus.

Using otoliths to estimate age and growth of a large Australian endemic monocanthid, Nelusetta ayraudi (Quoy and Gaimard, 1824)

Nelusetta ayraudi (the ocean leatherjacket) is an endemic Australian monacanthid species distributed from North West Cape (Western Australia) south to southern Queensland. The commercial and recreational fisheries targeting Nelusetta ayraudi have expanded substantially along the coast of New South Wales (NSW) in recent years but there exists little biological information on which to base effective management of this growing fishery. World-wide, only a few studies have aged monacanthids. Of these, researchers have interpreted periodic increments in bony structures such as vertebrae and anterior dorsal spines in preference to those found in otoliths. In this study we estimated age of N. ayraudi by counting growth increments in sectioned otoliths. The periodicity of increment formation was validated using a vital stain, (oxy-tetracycline), injected into young-of-the-year fish. Growth was rapid especially as juveniles with N. ayraudi attaining approximately 220 mm after 1 year and 340 mm after 2 years. No differences in growth rates were detected between sexes or between fish captured at different latitudes (zones). The largest male (605 mm, Total Length—TL) and female (656 mm, TL) were both recorded from northern NSW, with both sexes attaining the maximum age of 6+ years from northern and southern NSW. The von Bertalanffy parameters describing growth for N. ayraudi were \( {L_\infty } \) = 591 mm (TL), k = 0.377 year−1 and to = −0.247 years.

Radiometric age confirmation and growth of a deep-water marine fish species: The bank rockfish, Sebastes rufus

The bank rockfish, Sebastes rufus, is part of a deep-water (31–454 m) rockfish community that is fished commercially off California and has experienced population decline. This species is considered very difficult to age with traditional methods of counting growth increments in otolith cross-sections, creating the need to confirm age estimates with an independent, objective method. We measured the disequilibria of 210Pb/ 226Ra in S. rufus otoliths to compare with ages estimated from traditional methods. Radiometric ages corroborated mean otolith increment counts, with closest agreement for the oldest samples. We conclude that it is appropriate to use traditional cross-section methods to estimate age for S. rufus. Further, our results suggest longevity of 50 years or more for this deep-water rockfish. von Bertalanffy growth parameters calculated from these confirmed ages (with 95% confidence limits) were: L ∞ = 488 mm (46.2) TL, K = 0.0482 (0.019), t o = −8.372 (4.91), n = 81 males; L ∞ = 594 mm (89.5) TL, K = 0.039 (0.018), t o = −6.96 (4.97), n = 86 females. Comparison of age data from our study with length at maturity data from other researchers indicates that S. rufus reach sexual maturity at approximately 15 years of age. Like other deep-water members of this genus, S. rufus is slow growing and matures at an advanced age, important characteristics to consider for management of the species.

Understanding octopus growth: patterns, variability and physiology

Octopuses are generally characterised by rapid non-asymptotic growth, with high individual variability. However, in situ octopus growth is not well understood. The lack of an ageing method has resulted in the majority of our understanding of octopus growth coming from laboratory studies. Despite not being applicable to cephalopods, Modal Progression Analysis (MPA) of length–frequency data is the most common method for examining in situ octopus growth. Recently, counting growth increments in beaks and vestigial shells, and quantifying lipofuscin in brain tissue, have all shown promise for the ageing octopus. Octopuses generally demonstrate two-phase growth in the laboratory, with physiological changes possibly associated with the switch between an initial rapid exponential phase and a slower power growth phase. Temperature and food ration and quality are key factors influencing the initial growth phase. Temperature, however, does not appear to affect the second phase in any consistent way, perhaps because maturity stage can influence the growth response. There may be basic differences in the mechanisms of octopus muscle growth compared with that of other cephalopods. Furthermore, higher relative maintenance energy expenditure, along with the low energy content of their prey, may account for the relatively slow growth of deep-sea octopuses compared to littoral species.

Age and growth of the Pacific grenadier (Coryphaenoides acrolepis) with age estimate validation using an improved radiometric ageing technique

Current and historic longevity estimates for the Pacific grenadier (Coryphaenoides acrolepis) range from 6 to greater than 60 years. Age estimates in this study using growth increment counts in thin otolith sections indicate the Pacific grenadier is a long-lived fish. To validate this growth information, age was determined using the radioactive disequilibria of 210Pb and 226Ra in otolith cores from adult Pacific grenadier. Radiometric ages closely agreed with age estimates from counting growth increments, which confirms their annual periodicity. Radiometric results indicate the Pacific grenadier can live at least 55.8 years (-7.4, +10.1 years). Growth increment counts from large fish indicate longevity may approach 73 years. Because the Pacific grenadier is long-lived and matures late in life, it may be vulnerable to heavy fishing pressure. Therefore, conservation measures need to be taken to sustain this rapidly developing fishery.

Validation of a technique for reconstructing daily patterns in the recruitment of coral reef damselfish

Counting growth increments in otoliths recently has become an accepted method of ageing tropical fishes, however, verification is essential for each new species. In this study, growth increments in otoliths of the juveniles of several coral reef damselfishes (Pomacentridae) were deposited daily and a distinct transition from wide to narrow increments coincided with settlement from the pelagic larval phase into the demersal habitat. Thus, the data of settlement for each individual fish could be calculated with acceptable accuracy. The daily pattern of recruitment to a coral reef was successfully reconstructed using the otoliths from a large sample of juvenile fish collected at the end of the breeding season. This was because the original pattern of settlement was preserved in the age distribution for at least 4 to 5 months. This application of otolith ageing techniques may be extended to reveal the temporal patterns of recruitment to many localities encompassing spatial scales larger than would be logistically possible using visual censuses.

Daily growth increments in otoliths of milkfish, Chanos chanos (Forsskål), larvae

The formation of daily growth increments of otoliths was studied in the reared larvae of milkfish. The first growth increment was formed during the yolk–sac reabsorption period c.2 days after hatching, and increment formation continued on a daily schedule regardless of growth rate. The initial incremental zone was of amorphous structure, and the subsequent incremental zone was of needle–shaped crystalline structure; the former structure was formed in the yolk–sac reabsorption period of the larva and the latter in the exogenous feeding period. Accordingly, ageing of milkfish larvae is possible by counting growth increments, and timings within the developmental stage of the larvae can be understood by examining the otolith microstructure.