Catch Curve Analysis Research Articles

Ordering the alphabet soup: Strategies to improve consistency and develop a framework of tools for fisheries science vocabulary

Quantitative methods for assessing the status of marine fish populations began in the 19th century with simple catch-curve analysis and have evolved through the decades to use more advanced integrated statistical modeling. The corresponding assessment documents that communicate model estimates to other scientists and fisheries managers, generally, have grown in length and complexity, often describing hundreds of parameter estimates and population dynamics. These documents use a wide range of synonyms or similar terms that can vary either within a single assessment document or among other documents within or across fisheries management regions. The lack of standardization of terms used in assessment documents can lead to challenges in scientific reviews, communicating scientific results to fisheries managers, and for understanding assessments from other management regions. We analyzed the text of 134 assessment documents used to communicate the results of assessment software to managers from the varying management regions in the United States, Australia, and European International Council for the Exploration of the Sea (ICES) to quantify the presence of synonyms or similar terms that are often used interchangeably and highlight ways in which the output language could be harmonized without modifying meaning. Next, we developed an open source web-based dictionary and schema for fisheries science where the community can propose and adopt terms to create an agreed upon terminology. Finally, looking forward to future development, we propose approaches to leverage pre-existing frameworks such as Google coding standards to guide the development of tools to merge long-term ecological data sets, name objects in code bases, and report output. While this guidance is tailored to fisheries practitioners working within the U.S. management system, we aim to align with international standards to increase consistency across the international fisheries science community.

Variations in life-history traits in exploited and unexploited populations of Perth herring (Nematalosa vlaminghi): evidence for density-dependent growth?

Context Fishing can reduce population biomass, allowing remaining individuals to grow faster and mature earlier because of greater resource availability, which potentially compensates for lost reproductive output over a shortened lifespan resulting from fishing mortality. Aims To compare life-history traits of Nematalosa vlaminghi, a long-lived (20 years), semi-anadromous fish endemic to south-western Australia, in exploited and unexploited populations living in similar environments. Methods Populations were sampled in 2016–2018. Total mortality (Z) was estimated using catch-curve analyses, allowing for annual recruitment variability. Maturation age and length was estimated by logistic regression analysis. Growth curves were fitted to length-at-age data. Key results Compared to the unexploited population, Z was 2.6 times greater, juvenile growth was more than twice as fast, and maturity was attained at least 3 years earlier in the unexploited population. Conclusions Results supported the hypothesis of faster growth in exploited populations because of density-dependent processes. Environmental factors may also have contributed to trait differences between populations. Implications Faster growth and earlier maturation may partly compensate for lost reproductive output in exploited populations, although severe age truncation owing to fishing is still likely to decrease population resilience in this species, irrespective of any compensatory density-dependent processes.

Population dynamics and stock assessment of two major eels (Muraenesox bagio and Congresox talabonoides) from the marine waters of Bangladesh

Muraenesox bagio (black eel) and Congresox talabonoides (brown eel) are two major eels (Muraenesocidae) species which are commercially significant in the marine catch of Bangladesh, but population dynamics and stock assessment of marine eel fishery in Bangladesh are yet to be studied. This study is the first endeavour to analyze the population dynamics and stock assessment of this marine eels collected from July 2021 to May 2022 using three length-based methods namely TropFishR, the Length Based-Spawning Potential Ratio (LB-SPR) & the length-Based Indicators (LBI) and two catch-based methods including Depletion-Based Stock Reduction Analysis (DB-SRA) and the Catch-Maximum Sustainable Yield (CMSY). A slightly positive allometric growth pattern (b=3.10) for the black eel and a negative allometric growth pattern (b=2.33) for the brown eel were observed in the length-weight relationship. The parameters of von Bertalanffy Growth Function (VBGF) and the linearized length-converted catch curve (LCCC) analysis for black eel and brown eel were L∞=190.67cm and 166.63cm, k=0.18 year-1 and 0.16 year-1, and the total mortality, Z=0.70 year-1 and 0.45 year-1. The eel fishery is calculated to be overfished due to overexploitation and the stock’s spawning biomass (SPR=19% for black eel and 21% for brown eel) is close to the limit reference point but well outside the targeted range because the majority of the catches were found to have below-maturity levels. This study advised an optimum length limit to catch from 93 to 114 cm for black eel and 83 to 101 cm for brown eel. Though the estimated reference points of the CMSY were more optimistic than those from the DB-SRA, the tendency of the status of eel stock has been displayed moving towards overexploitation from a safe stock scenario. This study, therefore, recommended an annual landing limit of 250 mt as OFL (Over fishing limit) for the next ten years in association with existing management measures to maintain the present stock biomass of eel fishery over the BMSY level.

A review of estimation methods for natural mortality and their performance in the context of fishery stock assessment

Natural mortality (M) is one of the most influential parameters in fisheries stock assessment and management. It relates directly to stock productivity and reference points used for fisheries management advice. Unfortunately, M is also very difficult to estimate, and hence very uncertain. Representing the uncertainty in M and how this influences estimates of management quantities is therefore an important component of conducting stock assessments. This paper outlines the range of methods available to estimate M for use in stock assessment. The methods include those based on maximum age, life history theory, relationships between “well-known” values for M (those found in the literature and based on data for the stock being assessed) and covariates, use of tagging data and catch curve analysis, and estimation within a single- or multi-species stock assessment model. All methods are likely subject to bias and imprecision due to incorrect assumptions and incomplete data. Furthermore, M is generally assumed to be constant over time, age, and sex - assumptions that are unlikely to be true for any stock. Based on our review, there is an obvious benefit to directly estimating M using data and within a stock assessment while assigning a prior based on empirical methods. This approach effectively uses all the available information while also representing the uncertainty. Carefully examining diagnostics and checking for model misspecification is required to ensure that the available data and stock assessment model assumptions are appropriately informative about M when it is estimated during the model fitting process. For situations where direct estimation is not possible (a condition found in data-limited to data-rich stock assessments), the use of multiple methods with robust sensitivity exploration is recommended. Even when direct data are integrated into a stock assessment, we recommend using other methods to estimate M and analysing the direct data outside the stock assessment model as diagnostic tools.

Something strange in the neighborhood: Diverging signals in stock assessment data for Northeast U.S. fish stocks

AbstractIn the Northeast U.S., many stock assessments have a history of problematic model diagnostics, with multiple age‐based assessments recently being rejected in the peer review process, and are not suitable for management advice. The role in which diverging signals in the coastwide bottom trawl survey may be contributing to assessment problems was explored here for 18 stocks in the region. Specifically, trends in total mortality (Z) estimated from catch curve analysis and a relative measure of the harvest rate (total catch/survey index; called relative F) were evaluated. Across stocks, relative F has declined over time, on average, since the mid‐1990s, yet Z has not for many stocks. Weak positive or even negative correlations between relative F and Z resulted for 13 stocks. This diverging signal appears to be contributing to assessment model performance, as larger retrospective patterns (a measure of assessment uncertainty) occurred for stocks with negative correlations between relative F and Z. While a variety of mechanisms could be involved in these diverging signals, the available evidence suggests that unreported catch and/or increasing natural mortality likely play a role to varying degrees for each stock.

Age, growth, and mortality of littlehead porgy, Calamus proridens, from southeast Florida coastal waters

Sectioned otoliths were used to age littlehead porgy Calamus proridens ( n = 737) from southeastern Florida recreational fisheries. Otolith sections contained easily identifiable annuli and were reliable structures for aging littlehead porgy up to 11 yrs. Opaque zones were deposited from March to June (peaking in April). Littlehead porgy ranged from 1 to 11 yrs and 220 to 385 mm total length (TL). Body size relationships were TL = 1.09 FL + 16.06 ( n = 3474, r2 = 0.95), FL = 0.87 TL – 1.15 ( n = 3474, r2 = 0.95), W = 4.76 × 10 –5 TL 2.80 ( n = 6722, r2 = 0.86), and W = 1.2 × 10 –4 FL 2.71 ( n = 3474, r2 = 0.90), where W is total weight (g) and FL is fork length (mm). Growth was not significantly different between two discrete geographic regions of Florida, and the von Bertalanffy growth equation was Lt = 335 (1 – e –0.41 ( t + 2.13) ) for all areas combined. The point estimate of natural mortality was M = 0.38, while age-specific estimates of M ranged from 0.60 to 0.41 yrs–1 for ages 1–11. Littlehead porgy were fully recruited to the headboat fishery by age- 3 and catch curve analysis resulted in an estimate of total mortality Z = 1.08 for ages 3–7+. This study reports first estimates of life history parameters for littlehead porgy from Atlantic waters of the southeastern United States.

Exceptional longevity in a lightly exploited, semi-anadromous clupeid (Perth herring Nematalosa vlaminghi) within a degraded estuarine environment.

Many anadromous (and semi-anadromous) fish species, which migrate from marine to freshwater ecosystems to spawn and to complete their life cycle, are currently threatened by habitat degradation in the upper parts of estuaries and rivers, where spawning and juvenile nursery areas occur. This situation pertains to Nematalosa vlaminghi, a semi-anadromous gizzard shad (Clupeidae: Dorosomatinae) endemic to south-western Australia. More information on the biology of N. vlaminghi is required for its effective management and conservation. This study estimated growth, longevity and natural mortality of N. vlaminghi. Ages were determined by counting validated annual growth increments in thin sections of sagittal otoliths. Fish were sampled in the Swan-Canning Estuary, which historically hosted the main commercial fishery for N. vlaminghi. Since the late 1990s, however, only very minor catches of this species have been taken from this estuary and none since 2007. Given the essentially unexploited state of the current population, the estimate of total mortality (Z, y-1 ) from the catch curve analysis in this study provides a direct estimate of natural mortality (M, y-1 ) for N. vlaminghi. Somatic growth during this study was substantially slower than that historically reported for N. vlaminghi. Various processes operating in this estuary since the 1970s may have contributed to slower growth, including increased hypoxia, higher primary productivity due to eutrophication and cessation of fishing for N. vlaminghi. The maximum observed age of 19.8 years for N. vlaminghi is the highest reported for any gizzard shad globally and one of the highest reported for any clupeid species. This exceptional longevity is likely part of a life-history strategy that allows N. vlaminghi, which exhibits substantial variation in annual recruitment success, to persist in the intermittently closed estuaries of south-western Australia where environmental factors, including low flow and hypoxia, can create unfavourable conditions for reproduction for extended periods.

Auxiliary diagnostic analyses used to detect model misspecification and highlight potential solutions in stock assessments: application to yellowfin tuna in the eastern Pacific Ocean

Abstract Integrated models (IMs) for stock assessment are simultaneously fit to diverse data sets to estimate parameters related to biological and fishery processes. Model misspecification may appear as contradictory signals in the data about these processes and may bias the estimate of quantities of interest. Auxiliary diagnostic analyses may be used to detect model misspecification and highlight potential solutions, but no set of good practices on what to use exist yet. In this study, we illustrate how to use auxiliary diagnostic analyses not only to identify model misspecification, but also to understand what data components provided information about abundance. The diagnostic tools included likelihood component profiles on the scaling parameter, age-structured production models, catch-curve analyses, and two novel analyses: empirical selectivity and monthly depletion models. While the likelihood profile indicated model misspecification, subsequent analyses were required to indicate the causes as unmodelled changes in selectivity and spatial structure of the population. The consistency between the catch-curve models, the monthly depletion models and the IM information on abundance comes from a strong signal shared by several purse-seine fisheries data sets: the length composition data informs absolute abundance while the indices of abundance constrain the trend in relative abundance.

Growth, mortality parameters and exploitation of the swimming crab Portunus trituberculatus (Miers, 1876) in the East China Sea

Based on the samples from bottom trawls collected during March to October 2020 in the East China Sea, growth parameters, mortality rate and recruitment pattern of the swimming crab, Portunus trituberculatus (Miers, 1876), were estimated using FiSAT II software. Parameters of the von Bertalanffy equation obtained by ELEFAN I for males and males respectively were: growth coefficient (k) -0.99 and 1.01, theoretical maximum carapace width (L∞) - 22.58 and 21.53 cm and theoretical age at length 0 (t 0 ) -0.1738 and -0.15785. Mortality parameters estimated by the length onverted catch curve analysis for males and females were: total mortality (Z) -4.26 and 4.65, natural mortality (M) -1.643 and 1.784 and fishing mortality (F) -2.617 and 2.866, for females and males, respectively. The stock recruitment showed a bimodal pattern, in which the main peak was from July to October and the second peak in February and March. The exploitation rates arrived at were 0.61 and 0.62 for females and males respectively, while the exploitation maximum (Emax) obtained were 0.63 and 0.61 in females and males respectively. The results showed that, female swimming crabs in the East China Sea grow faster and reach larger carapace width than males and the current exploitation rate is very high and close to the value for maximum yield, indicating overfishing. Keywords: Biological parameters, East China Sea, Growth, Mortality, Portunus trituberculatus

High bycatch rates of manta and devil rays in the "small-scale" artisanal fisheries of Sri Lanka.

BackgroundExpanding fisheries in developing nations like Sri Lanka have a significant impact on threatened marine species such as elasmobranchs. Manta and devil (mobulid) rays have some of the most conservative life history strategies of any elasmobranch, and even low to moderate levels of bycatch from gillnet fisheries may lead to significant population declines. A lack of information on life history, demographics, population trends, and fisheries impacts hinders effective management measures for these species.MethodWe report on mobulid fishery landings over nine years between 2011 and 2020 across 38 landing sites in Sri Lanka. We collected data on catch numbers, body sizes, sex, and maturity status for five mobulid species. We used a Bayesian state-space model to estimate monthly country-wide catch rates and total annual landings of mobulid rays. We used catch curve analyses to estimate total mortality for Mobula mobular, and evaluated trends in recorded body sizes across the study period for M. mobular, M. birostris, M. tarapacana and M. thurstoni.ResultsWe find that catch rates have declined an order of magnitude for all species across the study period, and that total annual captures of mobulid rays by the Sri Lankan artisanal fishing fleet exceed the estimated annual captures of mobulids in all global, industrial purse seine fisheries combined. Catch curve analyses suggest that M. mobular is being fished at rates far above the species’ intrinsic population growth rate, and the average sizes of all mobulids in the fishery except for M. birostris are declining. Collectively, these findings suggest overfishing of mobulid ray populations in the northern Indian Ocean by Sri Lankan artisanal fisheries. We recommend strengthening the management of these species through improved implementation of CITES, CMS, and regional fisheries management actions. In addition, we report on the demographic characteristics of mobulids landed in Sri Lanka and provide the first record of M. eregoodoo in the country.

Stock assessment of Nile tilapia Oreochromis niloticus (Linnaeus 1758) in Lake Tana, Ethiopia

Nile tilapia Oreochromis niloticus is a commercially important fish species in the Lake Tana fishery and contributes to 65% of the total annual catch. This study estimated the maximum sustainable yield (MSY) and effort at maximum sustainable yield (fMSY) for the O. niloticus fishery using the Thompson and Bell yield prediction model. Catch and effort data from four representative landing sites were collected daily from June 2016 to May 2017 and used to estimate the total mortality coefficient (Z) using catch curve analysis, natural mortality (M) using Pauly’s empirical formula, and fishing mortality (F) as F = Z − M. Population abundance was evaluated using the Jones length-based cohort analysis model. The estimated Z, M and F values were 1.1, 0.52, and 0.49 per year, respectively. In total, 5 077 tons of O. niloticus were produced, which exceeds the MSY of 4 904 tons per year that could be obtained from the fishery at an F0.1. Consequently, the recommendation is to reduce the fishing effort by 15%. Collection of catch-and- effort data from more landing sites, over an extended period, could improve the yield estimates and this should be considered in conjunction with a bioeconomic analysis in future.

Daily ageing to delineate population dynamics of the invasive fish Gambusia holbrooki: implications for management and control

Despite the high global invasion profile of Gambusia holbrooki, there is limited knowledge of its population dynamics, especially biological parameters for fine-scale delineation of recruitment events that can provide a basis for controlling this short-lived invasive species. Key to this is daily ageing of otoliths, and in this study 193 (~ 50%) of 394 wild fish sampled from an invaded wetland were successfully aged. Increment counts of growth rings in otoliths from aquaria-reared G. holbrooki did not correspond 1:1 to their known ages but were significantly correlated (P < 0.05, R2 = 0.92), suggesting the use of linear relationships could nevertheless be used to estimate the age of wild-caught fish. Mean daily growth rate estimated for spring-summer cohorts (0.28 mm/day) was much greater than that of winter cohorts (0.12 mm/day). A natural mortality rate of 0.01 day− 1 for females was estimated by catch-curve analysis via length to age conversion based on the growth relationship. Birth rate closely correlated with changes in water temperature with a peak reproduction in January (Austral summer) at the study site. This study, for the first time, used daily age estimates of G. holbrooki to quantitatively examine population dynamics, which can be used to investigate invasive dynamics and choice of pest control strategies, including their scheduling and assessment.

Some biological parameters of Glossogobius aureus population from the Mekong Delta

Glossogobius aureus is an important commercial fish for food supply and has been caught increasingly, but data on its population biology is limited. The present study was carried out along coastlines from Soc Trang to Bac Lieu, southern Vietnam to contribute new information on the biological characteristics of G. aureus population. Data analysis of length-frequency distribution of 666 individuals showed that the equation of von Bertalanffy curve of this species was . The species displayed 4.47 y longevity and 2.75 in the growth performance. The length-converted catch curve analysis showed that the fishing, natural and total mortalities were 2.73 yr-1, 1.52 yr-1 and 4.25 yr-1 respectively and fish exploitation rate was 0.64. There was one recruitment peak in July and the analyses of relative yield-per-recruit and biomass-per-recruit gave Emax=0.408, E0.1=0.284 and E0.5=0.404. This goby is potentially an aquaculture species due to its high growth rate. The fish stock has been overfished, so the gill net mesh size should be increased and fish should not be caught during the recruitment period for sustainable management.

Historical and contemporary movement and survival rates of walleye (Sander vitreus) in Lake Winnipeg, Canada

Understanding patterns of fish movement in large lake ecosystems is essential for determining appropriate management actions as differences in movement behaviour can influence life history traits such as growth and survival. Lake Winnipeg in Manitoba, Canada supports the 2nd largest walleye (Sander vitreus) commercial fishery in North America. We used mark-recapture models to determine movement and estimate survival of walleye between basins of Lake Winnipeg in historical and contemporary contexts, comparing a tag-recovery study completed historically during 1974–1977 with a contemporary (2017–2019) acoustic telemetry study. Mark-recapture models revealed comparably low but detectable annual transitions between basins from historical (0.3–1.2%) and contemporary datasets (7–8.5%). Historically, fish > 300 mm more frequently moved in a south to north direction. Contemporary estimates suggest similar length-based directionality in that fish > 350 mm were always more likely to move in a south-north direction. Contemporary annual survival derived from mark-recapture models ranged between 27 and 45% and 64.3% when derived from catch curve analysis, while independently derived annual historical survival estimates ranged between 50 and 69% and 45.5% from catch curve analysis. Using the contemporary dataset, we also observed seasonal variation in movement and survival between basins, with the greatest movement across the lake occurring during the fall. Our results demonstrate a persisting pattern of low but measurable movement, suggesting between basin movement is not unusual for Lake Winnipeg. Further, low walleye survival rates reported here for the two time periods studied, support recent management actions to reduce fishing pressure across the lake.

Age, growth, and mortality of starspotted smooth-hound, Mustelus manazo (Bleeker, 1854) in southern West Nusa Tenggara waters

Mustelus manazo (Starspotted smooth-hound shark) is one of the important catch for small scale fisheries in West Nusa Tenggara. This species belongs to the family Triakidae. According to the IUCN Red List, the conservation status of this species is data deficient, which means that there is insufficient information to conduct a proper assessment of conservation status. The objective of this study is to estimate the age, growth and mortality of M. manazo in southern West Nusa Tenggara waters. Length data were collected from January to December 2016 in Tanjung Luar Port, West Nusa Tenggara. Electronic length-frequency analysis (ELEFAN) in R Statistics with package “TropFishR” was used to estimate the population parameter. Length converted catch curve analysis was used to estimate the total mortality. The results showed that von Bertalanffy growth model for male was Lt=122 (1-e(-0.1(t+0.01))), for female was Lt=130 (1-e(-0.18(t+0.02))) and for combined sex was Lt=132 (1-e(-0.1(t+0.01))). Total mortality was estimated at 0.25 year −1. The results from this study represent basic information to support fisheries management of M. manazo in Indonesia.

Estimating mortality for the assessment of a small-scale fishery: Lane snapper (Lutjanus synagris) in Honduras

Gillnets are very common in small-scale fisheries. However, data obtained using gillnets are biased because of their size selectivity, making accurate estimation of mortality difficult. This study applied various methods to estimate total, natural, and fishing mortality, using data for Lane Snapper (Lutjanus synagris) collected in Tela, Honduras. Total mortality was estimated using a catch-curve analysis with and without accounting for size-selectivity using fitted selectivity curves, the Chapman and Robson method, and Heincke’s method. Gillnet selectivity of Lane Snapper was best characterized by a skewed normal selectivity curve. The catch-curve method in the absence of correction for gear selectivity produced greater total mortality estimates than the Chapman and Robson and Heincke’s methods, with substantial variation among the three methods. Natural mortality estimates were consistent among five methods: Lorenzen, Peterson and Wroblewski, Sekharan, “FishLife” R package and Pauly’s method. Consequently, variation among fishing mortality estimates was primarily the result of variation in estimates of total mortality. Our results suggest that accounting for gear selectivity is critically important when assessing and managing small-scale fisheries.

Population structure of Nile tilapia and its impact on fisheries of a tropical impacted reservoir, Central India

Length-frequency data of Nile tilapia (Oreochromis niloticus) was studied using 1250 specimens of both sexes combined with maximum length and weight of 44.5cm (TL) and 1050g respectively through gill net catch at different landing sites of Halali Reservoir, Madhya Pradesh. The data were grouped into classes of 10-mm intervals and various parameters of population dynamics of fish were analysed and computed using the FiSAT-II software package (FAO-ICLARM Stock Assessment Tools). The length-weight parameters were found to be at W = 0.001L 2.96 where b = 2.96 and a = 0.001. Growth parameters L∞ and K of the species were L∞ = 46.73cm and K= 0.63/year respectively; the annual rates of natural (M) and fishing mortality (F) were found to be 0.60 and 0.72 respectively. The estimated values for the exploitation rate (E) using the length-converted catch curve and virtual population analysis were 0.54 and 0.42 respectively. The recruitment pattern shows that O. niloticus was recruited in the fishery during April with one peak. Based on the data analysis, the stock in the Halali Reservoir does not exceed the maximum fishing pressure (Emax = 0.55) and there is selective mortality towards adult fish sizes. The introduction of Nile tilapia improved the total catch per unit of effort (CPUE), as well as increased the number of active fishers. Conversely, a significant reduction in the CPUE of other commercially important indigenous species was observed after the introduction of Nile tilapia in the reservoir. Therefore, for management purpose, this study suggests that the existing effort in terms of gill net mesh size which target size (TL-15.0 to 25.0cm) individuals of length group is to be increased to exert more fishing pressure on Nile tilapia population in the reservoir to decline its abundance in the long term.

Growth and Mortality of Sillago sihama (Forsskål) from Karachi Coast, Pakistan

Length frequency data of silver sillago, Sillago sihama (Forsskål) were collected and measured from the fisherman catches using beach seines and handlines, at random, during 2012 from the Karachi coast of Pakistan. In this study, 1846 fish individuals (male and female combined) were collected ranging from 10 to 24 cm with dominant individuals ranged 12 to 16 cm (total length). Weight ranging was measured from 9 to 110 g. The above length-frequency data were analysed for the estimation of growth and mortality parameters. The power coefficient b of length-weight, the relationship was estimated at 2.9177. The estimated von Bertalanffy growth, function parameters of 25.20 cm (L∞) and 1.00 year-1 (K) were calculated by ELEFAN method equipped on FiSAT computer package. With length-converted catch curve analysis, the total mortality rate (Z) and its 95% confidence interval were 2.42 (2.174-2.669) year-1. The natural mortality rate (M) was 1.84 year-1 calculated with Pauly’s equation (the annual average seawater temperature was 27°C). Therefore, the fishing mortality rate was Z-M= 0.5787year-1. The exploitation ratio (E) estimated as F/Z=0.239 which is less than biological reference point (0.5), therefore it indicates that the stock of S. sihama was exploited at managed.

Biological and population parameters of Tiger Shark Galeocerdo cuvier, landed in Tanjung Luar, West Nusa Tenggara

Tiger shark is one of the important catch for small scale fisheries in West Nusa Tenggara. It is considered nearly threatened according the IUCN, thus information regarding to its estimated population is needed for conservative efforts. This study aimed to estimate the biological and population parameters of the tiger shark in Indonesia. Length data were collected from March to December 2018 in Tanjung Luar Port, West Nusa Tenggara. The length-weight relationship was calculated using equation W=aLb. Electronic length-frequency analysis (ELEFAN) in R Statistics with package “TropFishR” was used to estimate the population parameter. Length converted catch curve (LCCC) analysis was used to estimate the total mortality of the species. The results showed the length-weight relationship for combined sex, male and female was similar to the equation W=0.000001L3.15. The growth pattern for this species was positive allometric which means that the growth of weight is faster than its length. Total mortality was estimated at 0.33/yr, with natural and fishing mortality of 0.16/yr and 0.17/yr, respectively. The results from this study should be able to provide the basic information to support fisheries management of tiger sharks in Indonesia.

Application of the extractable lipofuscin aging method to estimate mortality and population dynamics of the burrowing shrimp, Neotrypaea californiensis

Lack of robust aging methods for crustaceans has inhibited the use of age-structured population models. Individuals are often classified based on body size, but differences in growth can bias parameter estimates. Our study applied the lipofuscin aging method combined with catch-curve analysis to estimate mortality rate for the burrowing shrimp, Neotrypaea californiensis. This species is an important member of the estuarine community with an impact on oyster production along the US West Coast. Randomized surveys were conducted from 2011 to 2014 to estimate population abundance, average density, and age structure in Yaquina Bay, Oregon. Mortality rate was estimated to be 0.719 yr−1 (95% CI; 0.633–0.793 yr−1) and did not vary significantly across cohorts. The spatial extent of the survey revealed spatial patterns in shrimp density that could be explained by variation in mortality and recruitment rates. This is the first study to apply lipofuscin aging to estimate population parameters of an estuarine crustacean and the methods we present can inform managers seeking to incorporate population ecology into management plans for N. californiensis and other crustacean species worldwide.