Fisheries Biologists Research Articles

How Fisheries Biologists Can Facilitate the Clean Energy Transition

Fisheries and aquatic biologists play a critical role in creating environmentally protective hydropower flow requirements that govern flow timing, frequency, magnitude, and rate of change. Hydropower's role in the U.S. electrical grid is expected to evolve in response to increased wind and solar generation as hydropower will be called upon to quickly ramp up and down in response to changes in wind and solar generation. For this reason, hydropower is expected to have increased value as fossil generation is phased out, even as rapid flow fluctuations linked with hydropower flexibility may strand fish, alter habitat, and create unsafe recreational conditions. We face a new challenge in facilitating the renewable energy transition—designing environmental flow requirements that protect against the impacts of flow fluctuations while allowing adequate hydropower flexibility to support a stable grid. In this paper, we discuss hydropower environmental flow requirements, operational flexibility, and electrical grid stability, their potential interactions, and opportunities to align environmental and power system needs to support healthy ecosystems, multiple water uses, and decarbonization of the electric grid.

Using de novo transcriptomes to decipher the relationships in cutthroat trout subspecies (Oncorhynchus clarkii).

For almost 200 years, the taxonomy of cutthroat trout (Oncorhynchus clarkii), a salmonid native to Western North America, has been in flux as ichthyologists and fisheries biologists have tried to describe the diversity within these fishes. Starting in the 1950s, Robert Behnke reexamined the cutthroat trout and identified 14 subspecies based on morphological traits, Pleistocene events, and modern geographic ranges. His designations became instrumental in recognizing and preserving the remaining diversity of cutthroat trout. Over time, molecular techniques (i.e. karyotypes, allozymes, mitochondrial DNA, SNPs, and microsatellite arrays) have largely reinforced Behnke's phylogenies, but have also revealed that some relationships are consistently weakly supported. To further resolve these relationships, we generated de novo transcriptomes for nine cutthroat subspecies, as well as a Bear River Bonneville form and two Colorado River lineages (blue and green). We present phylogenies of these subspecies generated from multiple sets of orthologous genes extracted from our transcriptomes. We confirm many of the relationships identified in previous morphological and molecular studies, as well as discuss the importance of significant differences apparent in our phylogenies from these studies within a geological perspective. Specific findings include three distinct clades: (1) Bear River Bonneville form and Yellowstone cutthroat trout; (2) Bonneville cutthroat trout (n = 2); and (3) Greenback and Rio Grande cutthroat trout. We also identify potential gene transfer between Bonneville cutthroat trout and a population of Colorado River green lineage cutthroat trout. Using these findings, it appears that additional groups warrant species-level consideration if other recent species elevations are retained.

Size-specific variations in the length-weight relationship and relative condition factor of Hilsa shad (Tenualosa ilisha) across its habitats in Bangladesh

The length-weight relationship (LWR) and relative condition factor are widely used as the most important biological parameters to infer the growth pattern and well-being of fishes. The aim of our study was to investigate the growth parameters of the LWR in different growth phases of Hilsa (Tenualosa ilisha), a flagship species of Bangladesh, and compare its relative condition factors across its major habitats. Fish from various rivers in Bangladesh and the Bay of Bengal were sampled, their length-weight growth parameters were measured and subjected to statistical analysis with pooled data from other studies. An isometric growth pattern in Hilsa was predominantly found in the size classes of 25 ≤ TL (total length) < 30, 30 ≤ TL < 35, and TL ≥ 40. However, the size class TL < 25 showed negative allometric growth with the value of the exponent (b, also known as growth coefficient) between 2.797 and 2.833. The highest weight-growth of Hilsa was within the size class of 35 ≤ TL < 40, with exponent values of 3.271–3.381 (positive allometric growth) across habitats. Our results revealed that the exponent value varied significantly (P < 0.05) between different size classes of Hilsa except between 30 ≤ TL < 35 and TL ≥ 40; however, no such significant differences in the exponent values were found across habitats. The Akaike Information Criterion value was lowest for the size-specific length-weight regression model of Hilsa, indicating it was the best-fit model compared to the habitat-specific and pooled sample models. The relative condition factor of Hilsa by habitat was found in the order of Meghna > Bay of Bengal > Andharmanik > Biskhali > Tetulia > Padma. Additionally, the relative physiological well-being of Hilsa from the river Padma and Tetulia was poor compared to that of other habitats. A more in-depth analysis is required to determine the factors that can influence Hilsa's growth and well-being in relation to habitat quality. The present findings have significant relevance for fisheries biologists and managers in understanding and interpreting Hilsa's ecology, relative well-being of populations of same or contrasting habitats, demographic assessment, and for better management of Hilsa in the future.

Why should scientists lead? To underpin policy on marine and polar ecosystems

Abstract I recount my personal history, beginning as a young fisherman, becoming an academic fisheries biologist, and ultimately a leader of institutions dedicated to marine and polar research, higher education, and advising policymakers. After my dissertation in the early 1990s, I embarked on an active research career at the Institute of Marine Research (IMR) in Bergen, Norway, developing a sonar method to estimate the abundance of schooling, pelagic fish. My career then transitioned to middle leadership—15 years as Section Leader and Research Director at IMR—followed by &amp;gt;10 years as a top leader for The University Centre in Svalbard, the National Institute of Nutrition and Seafood Research, and finally the Norwegian Polar Institute. I describe the major challenges, opportunities, and processes these leadership roles have entailed. I hope to send a positive message about the influential role of science, and the necessity of clear communication of results and advice at a time when there is a sense of urgency.

Length frequency distribution, length-weight relationship and condition factors of Hilsa Shad, Tenualosa ilisha from Bangladesh

Hilsa shad, Tenualosa ilisha, a cherished and economically vital species, thrives in the waters of Bangladesh. It holds a prominent role in bolstering the nation's food security and influencing the ecological dynamics of aquatic ecosystems along the Bangladeshi coast and estuaries. This comprehensive study encompasses data collection efforts on the Hilsa fish species, conducted at 12 commercial landing centers throughout Bangladesh over the course of 2020. The study describes some fundamental components, including length frequency distribution, length-weight relationships, and condition factors, offers invaluable insights into the growth, health, and overall well-being of Hilsa population. Notably, the length-weight relationship analysis revealed size ranges of 11.5-59.2 cm and 11.0-49.0 cm total length for females and males, respectively. The observed b values indicated positive allometric growth (b &gt; 3.00) for female population and negative allometric growth (b &lt; 3.00) for male population in the length-weight relationship. Among the condition factors scrutinized, Fulton's condition factor emerged as the most reliable indicator for assessing the health and condition of the Hilsa population. This study offers valuable insights for biologists, aiding in the assessment of the species' status and providing essential information for fishery biologists and conservation biologists. Such insights are instrumental in the management and ultimate conservation of this iconic species in Bangladesh.

The management of common carp fisheries using spawning potential ratio in the southeast of the Caspian Sea

AbstractSpawning potential ratio (SPR) is an important index used by fisheries biologists and managers to determine how a fishery should be harvested to prevent recruitment overfishing. In the southeastern Caspian Sea, Iran, 3430 common carp Cyprinus carpio were caught by beach seine in 2‐week intervals of two fishing seasons in 2019 and 2020. Fork length (FL) was measured to the nearest 1 cm. The age and maturity stage of 434 specimens, including 236 females and 198 males, were estimated by scale and gonad microscopic examinations. Estimated L∞ was 71.9 and K (growth constant) was 0.09. Instantaneous total mortality (Z) was 1.08, natural mortality (M) was 0.18, and fishing mortality (F) was 0.9. Estimated SPR at current fishing mortality (0.18) was lower than the reference point (0.4). Our findings indicated that fishing mortality should be reduced to F = 0.38 for C. carpio to meet the SPR reference point of 0.4. Further, higher minimum length limits should be set to reduce fishing mortality, and catch quotas for fishing cooperative corporations should be considered to meet the 40% SPR threshold.

Effect of feeding history on metabolic rate of largemouth bass (Micropterus nigricans): implications for bioenergetics models

Metabolic rate is a key parameter in fish energy budgets that strongly influences the output of bioenergetics models. In this study, we tested the hypothesis that metabolic rate varies with growth history of age-1 largemouth bass Micropterus nigricans Cuvier, 1828. Two groups of fish were fed alternating maintenance or ad libitum rations of fathead minnow Pimephales promelas Rafinesque, 1820, so that over a 9-week period, initial and ending size of fish was similar. After 9 weeks, oxygen consumption was measured using static, closed respirometry. Although final body weight was similar between the two groups (means, 104–108 g), specific oxygen consumption for fish fed maintenance rations (0.094 mg O2 g−2 h−1) was 38% less than that measured for fish fed ad libitum (0.152 mg O2 g−2 h−1). Bioenergetics estimates of food consumption were similar to observed values for fish fed ad libitum (∼7% error), but for fish fed maintenance rations, the model overestimated food consumption by 65%. By accounting for changes in metabolic rate owing to reduced feeding, error in model estimates of food consumption was reduced. These findings shed new insight into factors associated with consumption-dependent error in bioenergetics models and highlight the importance of feeding history on metabolic rate of fish. Incorporating growth-dependent metabolism into bioenergetics models can improve model accuracy and allow fisheries biologists to make more informed decisions regarding fish growth and energetics.

Revisiting and redefining return rate for determination of the precise growth status of a species.

Growth curve models play an instrumental role in quantifying the growth of biological processes and have immense practical applications across all disciplines. The most popular growth metric to capture the species fitness is the "Relative Growth Rate" in this domain. The different growth laws, such as exponential, logistic, Gompertz, power, and generalized Gompertz or generalized logistic, can be characterized based on the monotonic behavior of the relative growth rate (RGR) to size or time. Thus, in this case, species fitness can be determined truly through RGR. However, in nature, RGR is often non-monotonic and specifically bell-shaped, especially in the situation when a species is adapting to a new environment [1]. In this case, species may experience with the same fitness (RGR) for two different time points. The species precise growth and maturity status cannot be determined from this RGR function. The instantaneous maturity rate (IMR), as proposed by [2], helps to determine the correct maturity status of the species. Nevertheless, the metric IMR suffers from severe drawbacks; (i) IMR is intractable for all non-integer values of a specific parameter. (ii) The measure depends on a model parameter. The mathematical expression of IMR possesses the term "carrying capacity" which is unknown to the experimenter. (iii) Note that for identifying the precise growth status of a species, it is also necessary to understand its response when the populations are deflected from their equilibrium position at carrying capacity. This is an established concept in population biology, popularly known as the return rate. However, IMR does not provide information on the species deflection rate at the steady state. Hence, we propose a new growth measure connected with the species return rate, termed the "reverse of relative of relative growth rate" (henceforth, RRRGR), which is treated as a proxy for the IMR, having similar mathematical properties. Finally, we introduce a stochastic RRRGR model for specifying precise species growth and status of maturity. We illustrate the model through numerical simulations and real fish data. We believe that this study would be helpful for fishery biologists in regulating the favorable conditions of growth so that the species can reach a steady state with optimum effort.

A reconceptualization of the interactions between spawning and growth in bony fish

Among fishery biologists and even ichthyologists, maturation and spawning of fish are viewed as processes that use “energy” that would otherwise be applied to somatic growth, which is supposed to explain why post-maturity growth in length tends to decline. This widespread conceptualization may be called the “reproductive drain hypothesis” (RDH). However, when growth is correctly viewed as involving body mass, and is thus expressed in weight, post-maturity turns out (in iteroparous bony fish whose maximum length exceeds 10 cm) to accelerate after first maturity, despite its energy cost. This, and other common observations flatly contradict the RDH, and the time has come to withdraw this hypothesis. As a contribution towards this task, we propose an alternative reconceptualization of fish spawning consistent with what is known about fish biology.

Nonlethal Tools to Identify Mass Ovarian Follicular Atresia in Burbot

AbstractSkipped spawning, or variation in spawning periodicity, occurs in many annual spawning fish species and is an important consideration for population management. We assessed plasma sex steroid concentrations and measured gonad size and ovarian follicle diameter as metrics to nonlethally identify mass ovarian follicular atresia, which may contribute to skipped spawning in Burbot Lota lota. We maintained wild fish in captivity and exposed them to increasing water temperatures during a 3-wk period before the spawning season to induce mass ovarian follicular atresia. We collected ovarian follicles, blood plasma, and gonadal sonograms from fish weekly between January 28, 2018, and March 25, 2018. We histologically analyzed ovarian follicles to confirm stage of maturity. We measured concentrations of plasma sex steroids testosterone (T) and estradiol-17β (E2) by radioimmunoassay. We measured gonad diameter and circumference by ultrasonography and ovarian follicle diameter by image analysis. Mean plasma T concentration decreased from 8.94 ng/mL during late vitellogenesis to 1.83 ng/mL during atresia, suggesting that plasma T concentrations may be used to identify mass ovarian follicular atresia. We do not recommend using plasma E2 concentrations to identify mass ovarian follicular atresia because E2 concentrations rapidly decreased during the completion of vitellogenesis and the initiation of atresia in Burbot; therefore, plasma E2 may not accurately identify mass ovarian follicular atresia. Mean gonad diameter measured by ultrasonography decreased from 4.05 cm during late vitellogenesis to 3.65 cm during atresia. Mean diameter of ovarian follicles decreased during the final week of the study, suggesting that ovarian follicle diameter may be used to identify advanced mass ovarian follicular atresia. The nonlethal tools assessed—plasma sex steroid concentrations, ultrasonography, and ovarian follicle diameter—enable fisheries biologists to determine the occurrence and frequency of mass ovarian follicular atresia among Burbot in Lake Roosevelt and may be applied to other Burbot populations.

A Collaborative Aerial Survey of Coastal Pelagic Species in Nearshore California Waters

Pacific Sardine Sardinops sagax and Northern Anchovy Engraulis mordax are commercially important West Coast fish stocks managed within the Coastal Pelagic Species (CPS) complex by the Pacific Fishery Management Council and National Marine Fisheries Service. Before 2020, survey indices used in Pacific Sardine stock assessments did not explicitly account for nearshore biomass, which presumably had been relatively small compared to the total biomass of the population, but since 2015, has been a more substantial component of total biomass. During the recent Pacific Sardine stock decline, the California Department of Fish and Wildlife and the California Wetfish Producers Association collaborated on an aerial survey off California to estimate nearshore (within 3,600 m from shore) CPS biomass to inform assessments. This project has also involved federal fisheries biologists and Pacific Fishery Management Council advisory bodies and committees, representing a unique collaborative effort to improve data used in CPS fisheries management. We will discuss successes, issues, and challenges in implementing this nontraditional survey and how these data can continue to inform future stock assessments.

Spawning Potential Ratio: A Key Metric Considered in Managing Florida’s Fisheries

From red drum to red snapper, many of Florida’s fisheries are managed with specific consideration given to a quantity called the Spawning Potential Ratio (SPR). This conspicuous acronym is an important metric to fisheries biologists and managers. It helps determine harvest size limits for fisheries and drives regulations for both commercial and recreational fisheries. However, SPR is not especially intuitive to the general public or even agency personnel and Extension agents. This publication is intended to describe what SPR is and explain how and why it is used in managing fish stocks. We think it will help people better understand fisheries management decisions, the documents describing them, and the science behind them.

Determination of Recharge Areas That Supply Decades Old Groundwater to Creeks Inhabited by the Threatened Okaloosa Darter

The Okaloosa darter (Etheostoma okaloosae) is a diminutive, perch-like, benthic fish that inhabits only six small, clear, and shallow creek systems that flow almost entirely within Eglin Air Force Base in the panhandle of northwest Florida. Listed as Endangered by the U.S. Fish and Wildlife Service (USFWS) in 1973, improvements in erosion control and habitat restoration led to the Okaloosa darter being downlisted from Endangered to Threatened in 2011. However, the long-term management of the species is hampered by the lack of knowledge of the spatial extent of the recharge areas that ultimately support creek flow through groundwater discharge. To address this lack of data, we collected groundwater samples from the sand and gravel aquifer beneath 11 headwater and 11 downgradient sites across six creek basins during February and December 2020. The groundwater samples were collected from 1 to 1.2 m beneath the creek bottom. Concentrations of sulfur hexafluoride (SF6) were analyzed and used to calculate groundwater age (residence time), and indicated that at the 11 headwater sites, recharge occurred between 11 and 28 years ago. Groundwater ages in downgradient parts of the same creeks indicated that recharge occurred between 5 and 25 years ago. When combined with representative values of hydraulic conductivity for the sand and gravel aquifer, the ages reveal that the extent of the maximum recharge distance from the sampling sites ranged from about 222 to 2011 m from the creeks. This new information can be used by natural resource managers as additional evidence to support the USFWS Recovery Plan and proposed delisting of the Okaloosa darter from the Endangered Species List. Moreover, these results may also be useful to fisheries biologists to incorporate groundwater inputs to facilitate fisheries management.

Tag retention in and effects of passive integrated transponder tagging on survival and swimming performance of a small-bodied darter.

Fisheries biologists have been hesitant to use passive integrated transponder (PIT) tags in small‐bodied fishes (40–200 mm TL) such as darters (Percidae: Etheostomatinae) because of the fishes' size and potential effect on swimming performance. The authors used constant acceleration trials to evaluate the swimming performance of Arkansas darters Etheostoma cragini in control (no incision or tag), sham (incision and suture) or PIT tagged (surgically implanted 8 × 1.4 mm intra‐peritoneal PIT tag) treatments. Tag retention and fish survival were monitored for up to 199 days post‐tagging. Maximum swimming velocity did not differ between control, sham and PIT tag treatments, nor was maximum swimming velocity affected by the tagging procedure. Tag retention was 100%, and the overall survival of tagged fish was 88% in the swimming study, and 100% in the long‐term study, suggesting that small PIT tags are suitable for use in darters. The authors include a brief meta‐analysis on the results reported by 20 studies that PIT tagged small‐bodied fishes, representing 38 species and nine families of freshwater fish.

Resurrecting an Idaho Icon: How Research and Management Reversed Declines of Native Westslope Cutthroat Trout

Westslope Cutthroat Trout Oncorhynchus clarkii lewisi (WCT), the dominant nonanadromous salmonid in central and northern Idaho, historically were extremely abundant and widely distributed. Despite restricted harvest methods and limits since 1899, many WCT populations declined and by the 1960s, populations in several major drainages were on the brink of collapse. In response, fisheries biologists began investigating WCT population dynamics, life histories, and habitat requirements and developed evidence‐based regulations and habitat restoration alternatives. Here we describe fluvial WCT case histories that illustrate how research and management collaborated to rebuild populations. The sustained and successful effort to restore fluvial WCT in Idaho offers insights to assist WCT recovery efforts elsewhere. Today, populations in many watersheds have been rehabilitated and WCT currently inhabit about 80% of their historical stream range. Despite continued threats, many Idaho WCT populations are relatively secure, provide unique recreational opportunities, and remain an important ecological, cultural, and economic resource.

Length-weight relationships and condition factors of Sardinella longiceps (Valenciennes, 1847) from Seeb, Sultanate of Oman

Decadal (from 1997 to 2009) comparative analysis of the length-weight relationship and condition factors of Indian Oil Sardine (Sardinella longiceps) of the Sultanate of Oman was studied for long-term management. The length-weight data were collected from Ministry of Agriculture, Fisheries and Water Resources, Sultanate of Oman. An isometric growth (b = 3) was seen in 1997, a positive allometric growth (b > 3) was observed between 2004 and 2009, and a negative allometric growth (b < 3) was observed in 2005, 2006 and 2007. Fulton’s condition factor in the studied years were 0.857, 0.897, 0.911, 0.902, 0.885 and 0.900, respectively. The results of this study can be used as a valuable tool by fishery biologists, managers and conservationists to carry out Sardinella longiceps stock assessments along the coast of Sultanate of Oman and its neighbouring countries.

The Overfishing Problem: Natural and Social Categories in Early Twentieth-Century Fisheries Science

This article looks at how fisheries biologists of the early twentieth century conceptualized and measured overfishing and attempted to make it a scientific object. Considering both theorizing and physical practices, the essay shows that categories and understandings of both the fishing industry and fisheries science were deeply and, at times, inextricably interwoven. Fish were both scientific and economic objects. The various models fisheries science used to understand the world reflected amalgamations of biological, physical, economic, and political factors. As a result, scientists had great difficulty stabilizing the concept of overfishing and many influential scholars into the 1930s even doubted the coherence of the concept. In light of recent literature in history of fisheries and environmental social sciences that critiques the infiltration of political and economic imperatives into fisheries and environmental sciences more generally, this essay highlights both how early fisheries scientists understood their field of study as the entire combination of interactions between political, economic, biological and physical factors and the work that was necessary to separate them.

A Molecular and Morphological Guide to the Pilose Crayfishes of Western North America

The Snake River pilose crayfish Pacifastacus connectens and pilose crayfish Pacifastacus gambelii are sister species endemic to western North America that require increased conservation attention due to apparent range declines. We report results of molecular analyses that sought to clarify where P. connectens and P. gambelii occur relative to each other as well as morphological analyses that sought to help nonspecialists reliably identify these species in the field. We conducted our analyses on voucher specimens recently collected from across the presumed native ranges of both pilose crayfish species. We sequenced the mitochondrial cytochrome c oxidase subunit I gene of these crayfish specimens and then built Bayesian and maximum likelihood phylogenetic trees on these sequence data. Next, we made a series of morphological measurements on crayfish specimens, which we analyzed as morphological ratios in a principal component analysis. We found that P. connectens represents a diverse polytomy of multiple lineages distributed in the middle Snake River watershed and adjacent Harney Basin, whereas P. gambelii represents a monophyletic lineage of extremely low genetic diversity distributed primarily in the upper Snake River watershed and adjacent Bonneville Basin. We also confirmed that the pilose crayfishes are morphologically distinct relative to each other, with P. connectens reliably possessing a narrow or acute rostrum and P. gambelii reliably possessing a broad or obtuse rostrum. Alternatively, some other morphological characters historically associated with the 2 pilose crayfish species were less reliable in differentiating P. connectens and P. gambelii. Our findings should help natural resource managers, like fisheries biologists, anticipate where the pilose crayfishes occur and identify them under field conditions. Future investigations into the taxonomic status and phylogenetic relationships between these crayfish species would benefit from high-throughput sequencing focused on the nuclear genome.

The relationships between body and otolith size of the blueline snapper Lutjanus coeruleolineatus (Rüppell, 1838) collected from the coasts of Oman, Arabian Sea

Relationships between fish length and otolith length and width were examined in the blueline snapper Lutjanus coeruleolineatus (Lutjanidae) collected from the coasts of Oman, Arabian Sea. The values of exponent b from the relationships between fish total length and otolith length and total length and otolith width were estimated representing the close fitness of otolith size with fish size. Both relationships were statistically significant, which means both otolith length and width can be used to retrieve the fish original size. The analysis of covariance (ANCOVA) was used to test the effect of the categorical factor of species in the fish length and otolith length relationship. This study represents the first reference available on the relationship of fish size and otolith size for L. coeruleolineatus in the Arabian Sea area. Results from this study will offer original data on quantitative biometric relationships between body and otolith measurements of fish species in Arabian Sea region. By obtaining the mathematical model showing the relationship of the otolith size and fish length will enable fisheries biologists to know the size of the fish that has been eaten an information which important for fish biologists.

Morphometric and meristic characters and condition factor of Acanthopagrus arabicus (Pisces: Sparidae) from Pakistan, North Arabian Sea

Morphological differences among stocks of Pakistan, North Arabian Sea yellow fin sea bream, Acanthopagrus arabicus, including Sindh and Balochistan coasts, were examined using morphometric and meristic characters. Collections were obtained from two main fish harbors, situated in two provinces of Pakistan from September 2017 to August 2018. Twenty morphometric and eight meristic characters were documented and correlation coefficient (r) was investigated with independent variable (total length) and dependent variable (other morphometric parameters). The results confirm that majority of morphometric characters are greatly correlated to total length in all seasons. The total length ranges from 12.00 - 41.00 cm and 13.00 - 36.00 cm whereas total weight ranges from 31.00 - 1236.00 g and 34.00 - 595.00 g were recorded for Acanthopagrus arabicus, which were collected from Karachi fish harbor and Dam, Sonmiani fish harbor respectively. Condition factor ranged from 1.431 to 1.678 at Karachi and from 1.595 to 1.930 at Sonmiani in different seasons. Our present study in future could be useful to the students, fisheries biologist and taxonomist for the correct identification and classification of A. arabicus found in different location of Pakistan as well as management and conservation of this species.