Canadian Salmon farm invaded by Sea Lions.

A Salmon farm on the coast of British Columbia has been invaded by a group of Sea Lions, raising alarm among conservation groups, who fear they may become habituated to the environment. The Rant Point Salmon Farm near Tofino was the subject of an 'invasion event' in mid-March, according to Cermaq, the Norwegian multinational that runs the site, along with several others on the coast of British Columbia, and at other sites in Norway and Chile. However, conservation groups were not informed of the event until Sunday 3 April, when a Whale-watching trip observed the Sea Lions moving in and out of pens.

 

A Sea Lion consuming a Salmon at the Rant Point Salmon Farm in British Columbia. Jérémy Mathieu/Clayoquot Action.

Several previous Sea Lion invasions have been recorded at Salmon Farms in British Columbia, resulting in heavy losses of Fish stocks (Sea Lions can consume up to three times their own bodymass in Fish each day, piling on fat which enables them to survive seasonal food shortages), and numerous Sea Lion deaths through entanglement. During a previous invasion at Rant Point in 2016, the Canadian Department of Fisheries allowed the company to shoot the offending Sea Lions, but this stance has not been repeated in 2022, with the same body insisting that only methods which remove the Animals without hurting them can be used. This is part of a wider change in policy on Salmon farming in Canada, which now wants to see the practice phased out by 2025, following years of campaigning by conservation and indigenous rights groups.

 

Sea Lions inside and outside Salmon Pens at the Rant Point Salmon Farm in British Columbia. Jérémy Mathieu/Clayoquot Action.

Salmon farming on the coast of British Columbia brings employment to the area, and enables farmers to access lucrative US markets easily, but, as in other areas where it is practiced, is strongly opposed by environmental groups. Farmed Salmon, which live at far higher densities than would naturally be the case, are seen as a reserve for Salmon diseases, which can go on to infect wild Salmon, with potentially devastating effects on wild populations. This has potential knock-on effects for many other species, including marine predators such as Sea Lions which rely upon them for food, but also Bears and even forest trees far from the shore. This is due to the complex life cycle of the Salmon, which spend much of their lives at sea, acquiring nutrients from marine sources, before swimming back up the rivers where they were born to mate, spawn, and die. Since most natural processes tend to wash nutrients downstream from the land to the sea, this makes Salmon important ecosystem engineers in British Colombia and other areas of natural temperate rainforests. 

Salmon farms are also seen as highly poluting. This is because Salmon are predatory Fish, requiring farmed Salmon to be fed with Fish meal (generally made from wild-caught Fish species not favoured as food by Humans, raising further concerns about links between Salmon farming and overfishing), with the effect that both waste food and Salmon droppings are potential environment-changing pollutants. Furthermore, the problem of infections spreading easily within Salmon farms often results in farmers dosing the water with antibiotics and other medications, causing further environmental problems, and potentially leading to the spread of anti-biotic resistance in marine pathogens.

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Leucosolenia qingdaoensis: A new species of Calcareous Sponge from Shandong Province, China.

Sponges (Porifera) are considered to be one of the most primitive forms of animals. They lack differentiated cells, and can reform if disassociated by (for example) shoving them through a sieve. On the other hand they cannot be considered colonies of single-celled organisms, as they have definite structures, bodies with more-or-less set shapes consisting of networks of pores and channels through which water is pumped; the individual cells feeding separately by filtering food from the water in these channels. They are the only extant group of animals with a fossil record that extends significantly into the Precambrian. Calcareous Sponges, Calcarea, are Sponges that have skeletons composed of calcium carbonate.

 

In a paper published in the journal ZooKeys on 22 January 2020, Yan-Ling Chu, Lin Gong, and Xin-Zheng Li, of the Institute of Oceanology, University, and Center for Ocean Mega-Science of the Chinese Academy of Sciences, and Laboratory for Marine Biology and Biotechnology at the Pilot National Laboratory for Marine Science and Technology, describe a new species of Calcareous Sponge from Shandong Province, China.

The family Leucosoleniidae is characterised by a branched and rarely anastomosed  cormus  and asconoid aquiferous system (branching and rarely connected tube-shaped body, whith pores covering the surface through which wated is taken in, then expenlled through the central tube vents) ; there is neither a common cortex nor a delimited inhalant or exhalant aquiferous system. The family includes three genera: Ascyssa, Ascute, and Leucosolenia. These can be easily distinguished by their skeletons: the skeleton of Ascyssa contains only diactines (needle-shaped skeletal elements with two points); the skeleton of Ascute exhibits giant longitudinal diactines forming a continuous layer on the external surface, and includes triactines and tetractines (three and four pointed skeletal elements); and the skeleton of Leucosolenia lacks any of the obvious characteristics of the other two genera. Instead, the skeleton of Leucosolenia is characterised by being composed of diactines, triactines and/or tetractines, without a reinforced external layer on the tubes.

The genus Leucosolenia comprises 40 living species worldwide, of which only three species, Leucosolenia microspinata, Leucosolenia salpinx, and Leucosolenia parthenopea, were named after 1950; 11 species were described by Ernst Haeckel between 1870 and 1872. The literature of this genus is relatively old, and the descriptions contained therein of the species of Leucosolenia were simple, almost without details and illustrations of the body shapes and spicules. Thus, a taxonomic revision of this genus is very difficult, and to date, no worldwide revision of the genus has been made.

Fifteen known species of Leucosolenia have been recorded from the Pacific. Seven species, Leucosolenia. eleanor, Leucosolenia minuta, Leucosolenia mollis, Leucosolenia pyriformis, Leucosolenia serica, Leucosolenia tenera, and Leucosolenia ventosa, have been reported from the Japanese waters; Sagimi Sea, Wakayama Prefecture, Onagawa Bay, Mie Prefecture, Matsushima Bay, Izushima, and Wagu Miye Prefecture, respectively. Leucosolenia macquariensis was reported from the west coast of Macquarie Island; Leucosolenia. australis was reported from Comau Fjord in Chile; Leucosolenia albatrossi was reported from Copper Island and the Komandorski Islands in the Aleutian Chain; Leucosolenia echinata and Leucosolenia. rosea were reported from New Zealand; Leucosolenia lucasi was reported from Port Phillip Heads, Australia; Leucosolenia nautilia  was reported from California; and Leucosolenia feuerlandica was reported from Tierra del Fuego, South America. Thus the majority of the Leucosolenia species reported from the Pacific are found on the coasts of Japans. The specimens from which the new species is described were found in the Yellow Sea, very close to Japan.

Distribution of Leucosolenia (A) location in the Pacific Ocean (B) detail of the localities on the Japanese coast: (1) Komandorski Islands (Leucosolenia albatrossi); (2) Comau Fjord (Leucosolenia australis); (3) Cook Strait, Poverty Bay, Kawakawa (Leucosolenia echinata); (4) Francisco Bay, California; Sukumo ôsima, Kôti Prefecture, Sagimi Sea (Leucosolenia eleanor); (5) Tierra del Fuego (Leucosolenia feuerlandica); (6) Port Phillip Heads, Australia, and New Zealand (Leucosolenia lucasi); (7) Macquarie Island (Leucosolenia macquariensis); (8) Wakayama Prefecture (Leucosolenia minuta); (9) Onagawa Bay (Leucosolenia mollis); (10) Monterey Bay, California (Leucosolenia nautilia); (11) Mie Prefecture (Leucosolenia pyriformis); (12) New Zealand (Leucosolenia rosea); (13) Yodomi, Sagami Sea (Leucosolenia serica); (14) Matsushima Bay, Onagawa Bay, Izushima (Leucosolenia tenera); (15) Wagu Miye Prefecture (Leucosolenia ventosa); (*) Qingdao (new species). Chu et al. (2020).

The new species is described upon the basis of two specimens collected from a scallop-breeding pond on southeastern Shandong Peninsula in 1984 and 1988, and stored in the collection of the Marine Biological Museum of the Institute of Oceanology of the Chinese Academy of Sciences. 

For examination of the spicules, a small piece of specimen was cut and placed in a 1.5 mL microcentrifuge tube to which 1000 μL of sodium hypochlorite (bleach) solution was added. The mixture was then vortexed, placed at environmental temperature, and vortexed occasionally during incubation until it was completely lysed. Next, the sample was centrifuged at 8000 rpm for 2 minutes, the supernatant was poured off, 1000 μL of distilled water was added, and the sample was again centrifuged at 8000 rpm for 2 minutes. This procedure was repeated four times, then the spicules were washed three times with 96% ethanol and then the spicules were preserved in one third ethanol solution.

Scanning electron microscopy was performed with a Hitachi S3400N. Preserved spicules for scanning electron microscopy were adhered to stubs with double-sided carbon conductive tape and coverslip. After dehydration, the spicules were coated with gold in a Hitachi MC1000.

Measurements of at least 20 spicules of each type were performed using a Nikon Eclipse Ni optical microscope with a micrometric eyepiece. The length from the tip to the base and the thickness at the base of each actine were measured. Photographs were taken with a Zeiss Stemi 2000-c stereomicroscope and a Nikon Eclipse Ni-U optical microscope equipped with a digital camera to evaluate difference between the length of the unpaired and paired actines of each type of triactine. For comparison with the new species, Chu et al. only selected those species of Leucosolenia reported from the Pacific Ocean.

The new species is named Leucosolenia qingdaoensis, where 'qingdaoensis' means 'from Qingdao', in reference to the city in Shandong where it was discovered. This Sponge is arborescent, consisting of many thin-walled tubes, which are copiously ramified but never anastomosed. The Sponge occurs as growth form. The oscula are terminal on erect tubes. The colour of the Sponge is white after being preserved in alcohol and in vivo. The external walls of the tubes are hairy, with diactines protruding at right or oblique angles from the body; the surface is minutely hispid, and the consistency is soft and fragile. The specimen described measures 21.32 × 3.38 mm (height × width). The wall of the Sponge body is very thin, and there is no fully developed inhalant system, the gap between the skeleton and the cell on the wall arrange evenly; only a small amount of cells is distributed on the thin sponge skeleton, which is a typical asconoid feature. All internal cavities of the Sponge are lined by choanocytes.

Leucosolenia qingdaoensis, (A) holotype, (B) paratype, (C) detail of oscula (stereo microscope), (D) detail of root-like structures (stereo microscope), (E) detail of oscula (optical microscope), (F) detail of rootlike structures (optical microscope); arrowhead pointing at the ostium. Chu et al. (2020).

The skeleton consists of multifarious diactines, sagittal triactines of two types, sagittal tetractines with bent apical actines and triactine-like basal actines; together these form the wall of the ascon-type Sponge body.

In the apical osculum, there are paired actines of triactines and tetractines, some additional tangential diactines, together forming a clear line dividing the apical oscula, and some radial diactines projecting beyond the apical osculum with different length.

In the Sponge body, the triactines and tetractines are regularly arranged, their paired actines are parallel to the apical oscula, and the unpaired actines point downward, with slight folding allowed, but never overlapping; in contrast to the triactines and tetractines, the diactines are arranged more irregularly but generally point downward.

In the root-like structures, the arrangement of triactines and tetractines is the same as that in the body, but the arrangement of diactines is different; most of them tangentially project beyond the surface, which results in the surface having a slightly hispid (bristly) appearance.

By observing the sponge tissue taken from different parts, it is clear that as the diameter of the tubes decreases, the contents of small diactines and small triactines increase. This observation can suggest that in the growth zone spiculogenesis is more intense.

There is only one type of diactine, though the diactines vary in size and shape, their width varies from 24 μm to 61 μm, the length of diactines vary from 43 μm to 421 μm but half of the diactines present a length of 200–300 μm. The shapes of the diactines are straight or slightly curved in different directions. The variation in Leucosolenia is very common and considerable.

Spicules of Leucosolenia qingdaoensis. (A1)–(A3) diactines; (B1)  triactines of type 1; (B2) triactines of type 2; (C1)–(C2) tetractines. Chu et al. (2020).

Two types of triactines are present, with actines straight or undulated. Their ends are generally sharp or asymmetrical. The paired actines are slightly curved. Some deformations are present. Type 1 triactines have paired actines longer than unpaired actines: the unpaired actines are 42–105 × 3–5 μm; the paired actines are 63–105 × 3–5 μm. Type 2 triactines have unpaired actines longer than paired ones: unpaired actines are 76–129 × 3–4 μm; paired actines are 60–104 × 3–4 μm.

A relatively small number of tetractines were observed, approximately 10 per 100 spicules, with straight and fusiform actines. The tetractines are similar to triactines but with the addition of apical actines, the apical actines are fairly stout and short, sharply pointed and curved: unpaired actines are 93–119 × 2–5 μm; paired actines are 50–93 × 2–5 μm; apical actines are 11–29 × 2–5 μm.

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Sepiella japonica: Paternity testing reveals polyandry in the Japanese Spineless Cuttlefish.

The Japanese Spineless Cuttlefish, Sepiella japonica, is a commercially important marine species in China. Production from wild stocks reached 60 000 tons in Zhejiang Province and accounted for more than 9.3% of provincial fishing catches in 1957. The wild population of Sepiella japonica has declined since the 1980s due to over-fishing and pollution. To enhance production, artificial breeding methods are being developed in China and successful aquaculture techniques have been established in recent years. However, studies have revealed that the populations and individual genetic diversity in this species has declined under artificial conditions.An important factor that affects the genetic diversity of a population is the effective population size which in turn is greatly influenced by the mating system of a species. The mating system influences effective population size through changing the number of individuals contributing to subsequent generations. In a polyandrous mating system, females mate with several males within a single reproductive cycle in which the clustered offspring are descended from multiple males. In such a mating system, effective population size increases, and, as a result, maximizes the genetic diversity of the offspring within a single reproductive season. Some studies have confirmed that a polyandrous mating system is frequent in marine Cephalopods including the  Common Octopus, Octopus vulgaris, Deep-sea Octopus, Graneledone boreopacifica, the Southern Reef Squid, Sepioteuthis australis, the Giant Cuttlefish, Sepia apama, the Longfin Inshore Squid, Loligo pealeii, and the Spear Sqiuid, Loligo bleekeri. The female of all these species carries stored sperm from more than one male, and the effective population size is therefore significantly higher. Previous studies have shown that female Sepiella japonica store sperm in the seminal receptacle found in the buccal membrane. All else being equal, long-term sperm storage enhances the opportunity for multiple matings of this species. Moreover, multiple matings of female Sepiella japonica has actually been observed. Polyandry, coupled with sperm storage, is therefore potentially an important reproductive strategy for maximizing the genetic diversity of offspring in Sepiella japonica.

In a paper published in the journal ZooKeys on 14 October 2019, Liqin Liu of the National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization and the National Engineering Research Center for Facilitated Marine Aquaculture at Zhejiang Ocean University, Yao Zhang and Xiaoyu Hu, also of the National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization, Zhenming Lü, also of the National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization and the National Engineering Research Center for Facilitated Marine Aquaculture, Bingjian Liu, again of the National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization, Li Hua Jiang, again of the National Engineering Research Center for Facilitated Marine Aquaculture, and Li Gong, once again of the National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization, examine the mating system of Sepiella japonica experimentally, in order to understand the role of polyandry in maintaining effective population size.

In recent years, multiple paternity in several marine species has been documented using different genetic markers including allozymes, DNA fingerprinting, Random Amplification of Polymorphic DNA, and microsatellites. Microsatellites are the preferred marker because they are widely distributed in the genomes of most organisms and are highly polymorphic. Paternity studies based on microsatellites have become increasingly common, and the number of studies using microsatellites has increased. Several microsatellite markers have been isolated and characterized for Sepiella japonica and used to evaluate the genetic structure of its populations. Liu et al. used the previously described microsatellite markers to investigate whether multiple paternity occurs in Sepiella japonica.

Sexually mature adult Sepiella japonica were obtained from the Fujian Shacheng Harbor Cultivation Base in Fujian Province, China. A sample of 200 wild adults was captured using traps and kept mixed into a cage (9 m3). Seawater parameters were continuously maintained at 25–27 °C and 23‰ salinity. From this sample, seven mating pairs were randomly chosen as breeders to produce the next generation. All behavioral interactions were recorded using closed-circuit television with infrared to observe individual animals. Each mating pair was gently captured and placed in a spawning tank until oviposition. Egg strings derived from each clutch were transferred to a hatchery tank. After hatching, 280 offspring were randomly collected for population genotyping, maintained in a tank until they reached a pre-determined age.

Total genomic DNA was isolated from each offspring and from the muscular tissue of the respective parents. Three microsatellite loci, chosen from four loci (CL168, CL327, CL3354, CL904) developed specifically for Sepiella japonica were used to study genotypes for parents and their offspring.

Parents and their offspring were genotyped by determining alleles at three of the four microsatellite loci. Liu et al. considered evidence from at least two loci to be necessary for estimation of multiple paternity, because evidence from one locus may have been caused by mutations or genotyping error. They determined paternal alleles through subtracting the maternal alleles from offspring in a brood. The minimum number of sires for a clutch was assigned by counting the number of paternal alleles at each locus. Any instance of more than two possible paternal alleles at any loci indicated multiple paternity in a clutch.

Mating behavior in Sepiella japonica involves courtship of a female by a male, and females may copulate with multiple males. Mating pairs mated in the head-to-head position during which males transfer spermatophores to the buccal membrane of the females or to an internal seminal receptacle. The spermatophores that are deposited around the buccal area extrude the sperm mass to form spermatangium. Then the spermatangia attach to the buccal membrane where slowly released sperm are used for fertilization. Liu et al. found that the male flushed water strongly when he was close to the female buccal area prior to mating with the female. This behavior is thought to dislodge sperm from previous males. They also found obvious courtship rituals and agonistic behaviors after sexual maturity. Males are generally capable of mating early in life (3–6 months maturity) and will continue to mate until senescence. However, the females do not generally lay eggs after copulating until fully mature. The duration of spawning in Sepiella japonica varied from 21 to 30 days. Females lay multiple eggs (from tens to hundreds of thousands) by extruding them from the ovary and then they die shortly after spawning.

Sepiella japonica mating in the head-to-head position. Liu et al. (2019).

Three of the four microsatellite markers were chosen to test paternity in seven offspring clutches. These loci exhibited three or more alleles and were polymorphic in each individual. Lui et al. chose the locus which followed Mendelian inheritance to analyze paternity. Two hundred and eighty-seven individuals were genotyped at three loci, seven adult females and 280 offspring. The analysis was highly reproducible. Lui et al. analyzed paternity including sampled males and non-sampled males that had copulated with females prior to capture.

Almost all females were heterozygous at these loci (CL168, CL327, CL3354, CL904), except for CL327 in the clutch B female. For clutches A and E, three different alleles which the father contributed were observed at the three chosen loci, suggesting that these two clutches had been sired by at least two males. The offspring of four females (B, C, D, and F) had three or four paternal alleles in each locus, and three paternal genotypes were observed in all loci. The number of paternal genotypes at these three loci indicated that females B, C, D, and F had mated with three different males. Within clutch G, five different alleles were detected at loci CL168 and CL3354, two of which were from maternal alleles. Clutch G showed four alleles for the locus CL904 in addition to the two alleles detected in the female. Four different paternal genotypes were estimated in clutch G, suggesting the female G was fertilized by at least four different males.

Lui et al. observed female Sepiella japonica mating with different males during the reproductive period, a behavior also recorded in other species of Cephalopods. The benefits of multiple mating not only may raise the potential for genetic diversity but also increases the possibility of offspring survival. It has previously been shown that female Southern Dumpling Squid, Euprymna tasmanica, that mated with different males had larger eggs than those that mated with one male, indicating that females may obtain nourishment from the seminal fluid of several males. Male Cephalopods exhibit 'flushing behavior' in which they remove fresh spermatangia from previous males. In the Golden Cuttlefish, Sepia esculenta, the males remove sperm by using the hectocotylus (a modified arm used by some male Cephalopods to transfer sperm to the female) instead of flushing water. The males in Lui et al.'s study also exhibited such behavior, flushing the buccal area of the female with water, when mating with a previously mated female.

Microsatellite markers are particularly useful in paternity studies because of their polymorphism, codominance, and repeatability. Cephalopod biologists have determined multiple paternity in many species, including Squid and the Deep-sea Octopus, Graneledone boreopacifica. In this study, at least three paternal allele genotypes were found in all seven clutches indicating that at least two males were responsible for each brood. This result was in accordance with previous studies where multiple paternity was also found in the Giant Cuttlefish, Sepia apama. Multiple paternity in Sepiella japonica offspring indicates that sperm from different males must be mixed within the female’s reproductive tract. These sperm deposited around the buccal mass were used differentially to fertilize eggs, after a process of sperm competition or mediation by female choice.

Despite the prevalence of multiple paternity in cephalopod species, these studies show widely differing incidences of multiple paternity. In Lui et al.'s study, multiple paternity was demonstrated in all sampled clutches (100%). In the Giant Cuttlefish, Sepia apama, one-third of the females mated with multiple males and 67% of females’ eggs had multiple sires. Several factors have been confirmed to be related to the variance in incidence of multiple paternity observed in cephalopod species, e.g., sperm allocation, mating systems, sperm competition, and female choice. Moreover, as suggested for the Spear Squid, Loligo bleekeri, males who were the last to mate fertilized 85–100% eggs in four broods tested. However, in the multiple paternity study of the Longfin Inshore Squid Loligo pealeii, the mate order is not the most important factor in determining paternity; however, no clear hypothesis has yet emerged to explain which factor is essential in the multiple paternity of Sepiella japonica. Further work should be carried out to understand paternity patterns and to investigate different factors affecting multiple paternity in this species.

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Eleven-and-a-half thousand of years of Clam use on the coasts of British Columbia.

Over the millennia, many peoples worldwide developed intimate knowledge of, and relationships with, particularly valued species of plants and animals. Tracking the development of these long-term human–species relationships requires temporally grounded records that provide insights into both the cultural and ecological sides of this equation. For instance, the archaeological faunal record can provide detailed information on the ecological and cultural effects of human–species interactions, whereas the palaeoecological record can provide insights into species ecology in the absence of significant human intervention. Taken together, these two records can offer a powerful lens through which to assess coupled social–ecological systems over broad spatial and temporal scales and can help establish ecological baselines for modern management. On the Northwest Coast of North America, clams are a valued cultural species with widespread importance that is reflected in origin stories, rituals language, and in the kilometers of deep and ancient shell middens that line the coastline. Detailed archaeological and ethnographic research indicates that Clams, especially Butter Clams, Saxidomus gigantea, and Littleneck Clam, Leukoma staminea, were eaten in abundance both seasonally and year round and both fresh and preserved. These species were a reliable, abundant, and easily harvested source of food that could be tended to increase abundance by applying various traditional cultivation techniques. One such technique, the building of rock-walled intertidal terraces called 'Clam gardens', expanded and enhanced Clam habitat and thus, Clam production.

In a paper published in the Proceedings of the National Academy of Sciences of the United States of America on 14 October 2019, Ginevra Toniello of the Department of Archaeology at Simon Fraser University, the Hakai Institute, and the Treaty, Lands and Resources Department of the Tsleil-Waututh Nation, Dana Lepofsky, also of the Department of Archaeology at Simon Fraser University, and the Hakai Institute, Gavia Lertzman-Lepofsky of the Department of Biological Sciences at Simon Fraser University, Anne Salomon, again of the Hakai Institute, and of the School of Resource and Environmental Management at Simon Fraser University, and Kirsten Rowell, of the Department of Biology at the University of Washington, and the Environmental Studies Program at the University of Colorado, compare Butter Clam size and growth patterns from different temporal, environmental, and cultural contexts spanning 11 500 years ago to the present, with the aim of understanding Clam use and mariculture (the cultivation of marine organisms for food) by Human populatins over this time period.

Complimenting the archaeological and ethnographic records, studies of subfossil and fossil Bivalves on the Northwest Coast have provided significant insights into the region’s palaeoecology. Such data have been used for reconstructing both preHuman and recent historical ecological conditions. To the best of Toniello et al.'s knowledge, no studies have combined both the archaeological and palaeoecological marine Bivalve records to fully explore the long-term relationships among Humans and Clams.

Toniello et al. investigate the historical ecology of Butter Clams throughout the Holocene along the northern coast of Quadra Island, Salish Sea, British Columbia through analyses of the palaeoecological, archaeological, and contemporary ecological records. Together, these records encompass 11 500 years of history, a period that spans the time before extensive human settlement to today. In their study sites in Kanish and Waiatt Bays, the coevolved history of Humans and Clams is reflected in the expansive archaeological shell middens with deposits dating to as old as 9000 years ago and the plethora of Clam gardens dating from sometime after 3500 years ago.

(A) Study sites on northern Quadra Island, British Columbia, showing Clam garden sites (blue dots), large midden settlement sites (yellow diamonds), and sampling sites (red stars). Toniello et al. (2019). (B) Clam gardens, Quadra Island. Clam garden built on soft sediment showing wall, Clam garden terrace, and 9000 year old midden. Living and dead (palaeo) Butter Clams were collected from the Clam garden terrace and the shell midden. Mark Wunsch/Greencoast Media in Toniello et al. (2019).

Based on their understanding of Clam life history, coastal ecology, and local cultural attributes, Toniello et al. predicted that Butter Clam sizes and lifespan increased over the last 11 500 years as environmental conditions became more favorable and as Humans altered the intensity and strategy with which they harvested and cultivated clams. Thet also predicted that today’s Butter Clams are not as productive as those in past environments, likely due to a combination of less favorable ocean conditions, habitats modified by modern development, and the absence of traditional, Indigenous mariculture practices. To evaluate these hypotheses, they estimated Butter Clam sizes at various ages with sclerochronological analyses (analysis of chemical variations in accretionary hard tissues) of Clam shells from 5 beach sites and from 3 contexts at these sites:  (1) palaeobeaches below Clam gardens that contain layers of Clams that died in situ (death assemblages) before Clam gardens were constructed, (2) terrestrial archaeological shell middens composed of Clams originally harvested from active Clam gardens, and (3) now largely defunct Clam garden beaches containing Clams that both are living and died relatively recently. Based on radiocarbon dating and stratigraphic context, Toniello et al. grouped these samples into seven temporal periods, each characterized by particular cultural and environmental attributes which they predicted would differentially influence lam growth, and asked what variables best predict Clam size across a spectrum of ages and age at death over the past 11 500 years.

As predicted, nonharvested clams (i.e., Clams that died in situ from natural mortality) show a steady increase in size at death and age at death from 11 500 to 11 000 years ago until the early-Late Holocene (4200 to 2900 years ago), corresponding to improving environmental conditions. In the midden (2800 to 2300 and 500 to 200 years ago) and living samples, Clams were harvested from active and inactive Clam gardens, respectively, and did not live out their full lifespans. Thus, the measurements do not evaluate natural mortality but rather, in the case of the middens, show the preferred size and age at which clams were harvested. However, in the Early Historic Period, where Clams died of natural mortality in Clam gardens, we can compare their age at death and size at death with the early-Late Holocene Clams. We find that the median age at death and size at death of the Early Historic Clams drop significantly and are 16 to 40% smaller than those in the early-Late Holocene samples (4200 to 2900 years old). In addition, the Early Historic samples are statistically indistinguishable from the Early Holocene time periods (11 500 to 11 000 and 10 900 to 9500 thousand years ago) when there was minimal Human presence on the Pacific Northwest coastal landscapes. Notably, Early Historic Period Clams grew in the years following 1782 AD when the Indigenous populations declined dramatically as a result of introduced diseases.

Butter Clams from 11 5 to 11 000 years ago (Left) and from 10 900 to 9500 years ago (Right), illustrating the differences in butter clam shell size in some samples. Toniello et al. (2019).

To further explore butter Clam growth rates Toniello et al. fitted growth curves of Clam growth increments in each of the seven time periods and compared estimated theoretical maximum Clam sizes. Visual inspection of the early life history growth in the growth curves suggests that the Clam growth trajectories across time periods broadly fit Toniello et al.'s predictions that Clams grow faster as environmental conditions become more favorable. Additionally, Clams from 11 500 to 11 000 years ago, Clams from 10 900 to 9500 years ago, and those from today appear to follow the same growth pattern and grow relatively slowly in their early years. In contrast, Clams living 4200 to 2900 years ago, the midden Clams harvested from Clam gardens (2800 to 2300 years ago and 500 to 200 years ago), and the Early Historic Clams all have a relatively faster growth trajectory in their early life history.

These growth curves allow Toniello et al. to compare the theoretical maximum length for the midden and living samples as if they were not harvested, assuming that earlier rates of growth in an individual are predictive of later growth rates. The estimated infered lengths of the 11 500 to 11 000 year old Clams are significantly smaller than most of the other time periods, except for the 10 900 to 9500 year old, Early Historic, and living specimens. This again suggests that Clams growing under modern conditions (in the last 200 years) reach sizes similar to Clams that lived in the Earliest Holocene. The infered length estimates further suggest that Clams from the middens, which were harvested from active Clam garden beaches, would have reached roughly the same maximum length as the nonharvested Clams in the early-Late Holocene. This suggests that Clams under intense human management have the potential to grow as large as the largest Clams living in environments with relatively few Humans. Toniello et al.'s estimates of potential length, combined with their empirical data together indicate that, as environmental conditions improve and as traditional management intensifies, Butter Clams have the capacity to grow to older ages and larger sizes than before.

For each individual Clam, Toniello et al. compared how size at age for the first 5 years changed across temporal category. Each size at age follows a roughly similar pattern and mostly parallels that of age at death, size at death, and infered maximum length. Toniello et al. found that, contrary to thei predictions, age 1 Clams in the Early Historic Period are bigger than all other times. By ages 4 and 5, Clams in all time categories except living and those from 10 900 to 9500 years agp are larger than those in the oldest period (11 500 to 11 000 years ago).

Toniello et al. compared the relative strength of evidence for several environmental and cultural attributes affecting Clam growth with a multimodel inference approach, allowing us to explore alternative mechanisms driving variation in size at age. Depending on the age of the individual, different terms are included in the model average. For young clams (ages 1 to 2), they found evidence that beach slope and sea surface temperature inversely affect size at age but are less important for clams ages 3 to 5, suggesting that young Clams are relatively more sensitive to changes in these factors. Coarse substrate has a strong positive influence on size at age for clams ages 1 to 5, with the strength of the effect being stronger as a Clam gets older compared with fine substrate. Similar to Fish, slight growth differences are more difficult to detect as Clams age and growth slows, and therefore, the effects that Toniello et al. detect in older clams are actually conservative. Taken together, the inclusion of more terms in the model average (slope, sea surface temperature, and substrate) for Clams ages 1 to 2 indicates that relatively more environmental factors influence the growth of younger Clams than older ones. As predicted, for Clams at all ages (1 to 5), the presence or absence of a Clam garden wall is an important factor affecting Clam growth, and the presence of a Clam garden results in a strong positive effect on size at age.

Similar factors affect both age at death and size at death, with Clam garden wall, slope, and substrate having the most influence. Not surprisingly, the presence of a Clam garden has a strong negative influence on both size at death and age at death, since most of the Clams from Clam gardens in the sample were harvested (midden samples from 2800 to 2300 years old and from 500 to 200 years ago and living), thus truncating their size and age at death. While substrate does not appear to affect age at death, size at death is affected by substrate, where coarse substrates result in larger size at death compared with fine substrates. This indicates that coarser substrates may be better for Clam growth. Flat and moderate intertidal beach slopes, typical of Clam gardens, result in older and larger age at death and size at death compared with steep beach slopes.

Toniello et al. also compared environmental and cultural factors affecting the growth curves and potential size. Substrate is the most important variable governing maximum infered potential size, where coarser substrates are associated with larger potential sizes, compared with fine substrates. Flat and moderate beach slopes exert a positive influence on potential size as compared with steep slopes.

Taken together, Toniello et al. show that not only are there several factors that influence size of a clam throughout its life but also, that the effects of these factors vary throughout the life of the clam. For instance, sea surface temperature appears to be negatively correlated with the size of Clams at age 1, but Toniello et al. did not detect an effect of sea surface temperature by age 2. The absence of effect in age 2 is at least in part due to the incongruity of comparing the millennia scale of sea surface temperature data with yearly-scale growth patterns of Clams that are individual snapshots of different years within that period of time. Similarly, flat and moderate beach slopes are negatively correlated with the size of Clams at ages 1 and/or 2 but do not appear in the model average for individuals ages 3 to 5. Clam gardens, however, have a positive effect on the growth of young clams as suggested by previous experimental data. Finally, coarse substrate, characteristic of the unwalled early-Late Holocene beaches as well as cultivated Clam gardens, appears to be beneficial to growth in all age categories, but the strength of this relationship increases with age.

With the retreat of the Cordilleran ice sheets roughly 13 500 years ago, coastal areas provided increased habitat for many species, including Humans and Bivalves. Toniello et al.'s earliest Butter Clam samples consist of subfossil death assemblages dating to 11 500 to 11 000 years. When alive, these Clams burrowed into silts, fine sands, and poorly drained glacial-marine clays; on steep beach slopes; and in relatively cold sea surface temperatures. These environmental conditions are not ideal habitats for this species of Clam, and not surprisingly, this contributed to the small size, young age at death, and slow growth of these Clams.

Butter clam environmental conditions began improving after about 11 000 years ago. These improvements include a transition to coarse (gravel–sand) substrate due to paraglacial deposits and hydrodynamic erosion, an increase in sea surface temperatures, and stabilizing sea levels. These factors likely contributed to increased phytoplankton productivity and more stable substrates for Bivalve settlement. These improved conditions are reflected in Toniello et al.'s measured and modeled data by relatively larger size and older age at death of the 4200 to 2900 year old intertidal subfossils compared with those from 11 500 to 11 000 years ago. However, the growth trajectories for young Clams are similar in these two time periods, which suggests similar ability to grow. Possibly, a decrease in mortality in the 4200 to 2900 years ago period allowed for more larger and older individuals in that period’s death assemblage.

The abundance of Early Holocene subfossil shells within the intertidal sediments suggests that these early Clam populations were not under significant predatory pressure by Humans. Based on the Early Holocene archaeological record elsewhere on Quadra Island, Toniello et al. suspect that Humans were visiting their study area at least by 10 000 years ago, but there is no known record of sustained settlement. However, even if early campsites were found in the study area, it would be difficult to explore the role of Clams in the Human diet, because the region’s acidic soils limit preservation of Clam shells in older archaeological deposits.

There is a temporal gap in our analysis for the period 9500 to 4200 years ago due to the absence of both midden and intertidal Clam samples. Although there are archaeological sites from this time, they have yet to be sampled for faunal analyses. Within the beach sediments, taphonomic factors are likely responsible for the lack of intertidal subfossil shells. In particular, the persistent wave action caused by relatively stable sea levels during this 5000 year period coupled with reduced sedimentation would have resulted in increased sediment erosion and the displacement and deterioration of intertidal subfossil shells. Before and after this time, the steady decline in sea level meant less wave action and thus, a regular influx of sediment that buried dead Clams quickly, making them more likely to be preserved in the intertidal sediment column.

When we pick up the palaeorecord again about 4000 years ago, we see that environmental conditions affecting Butter Clam growth continued to improve. These improvements, which differentially affect different age classes, include the further accumulation of coarse (gravel–sand) substrates and stabilized sea surface temperatures. These beneficial environmental conditions are reflected in the trend of increased age at death, size at death, and maximum size of the 4200 to 2900 year old intertidal subfossil Butter Clams as compared with those from earlier in the Holocene. The large size of these Clams must have been appealing to Human harvesters, who began to harvest Clams in earnest by about 5000 years ago as indicated by the local preservation of shells in archaeological settlement sites. However, the prevalence of long-lived Clams in Toniello et al.'s intertidal Clam death assemblage, dating to 4200 to 2900 years ago and originating from one particular beach (EbSh-77) 0.8 km from the nearest village, suggests that this location was not under heavy predatory pressure by Humans. Toniello et al. suspect that this in turn reflects the fact that Humans were focusing their harvesting on beaches immediately adjacent to their settlements.

After about 3500 years ago, Human–Clam relationships in Toniello et al.'s study area intensify as indicated by the building of some of the first Clam gardens. At this time, large settlements increase in number in Kanish and Waiatt Bays, filling all inhabitable coastal landforms and reflecting an increase in local human populations. By about 2700 years ago, Clam harvesting was so intensive that subfossil Clams are virtually absent from intertidal deposits, and instead, there are large quantities of harvested Clam shells in the middens. Clam garden construction was likely iteratively related to increasing Human populations, both as an impetus for enhancing a reliable and productive food source and trade item and in turn, by allowing for the increasingly larger Human population and complex social relations.

Despite intensive harvesting, several lines of evidence suggest that, as a result of traditional management practices, Clam populations in the study area thrived throughout the Late Holocene. In general, building Clam gardens increased the accessibility of Clams to Human harvesters by decreasing beach slope, increasing the amount of beach exposed during low tide, and increasing the proximity of Clams to Human settlements. Such increased accessibility of existing Clam beaches could easily result in overharvesting. However, in our study area, this potential increase in harvesting pressure was offset by generations of Indigenous peoples building Clam gardens, thereby increasing the viable Clam habitat. Toniello et al. suggest that creation of this new Clam habitat combined with other cultivation methods (e.g., tilling, removal of nonHuman predators, altering substrate, rock removal) and spatially explicit designated access rights ensured an ongoing, sustainable harvest of Clams. Furthermore the creation of the coarse sediment garden terrace and associated rock wall had the added benefit of increasing the abundance and availability of other edible marine foods (e.g., Red Rock Crabs, Sea Cucumbers, Snails, a variety of Seaweeds).

In two different ways, the size of the Clams in the middens in  Toniello et al.'s study supports their inferences about the development of sustainable traditional harvesting practices. The first is the comparable estimated  maximum size of Clams from the nonwalled early-Late Holocene beaches (4200 to 2900 years old) and those from the heavily harvested Clam gardens in the middens (2800 to 2300 years old and 500 to 200 years old). Given the importance of substrate to the growth of young and old Clams, Toniello et al. surmise that the similarity in Clam size in these two time periods is in large part due to the coarse sediment substrate in both the naturally productive beaches and the created Clam garden habitats.

The second way in which Toniello et al.'s midden data support inferences of sustainable harvest practices is that there is no indication of fishing pressure selection, such as a gradual decline in harvested Clam size over time (i.e., compare 2800 to 2300 years ago and 500 to 200 years ago). Furthermore, the majority (62%) of clams within the midden samples are larger than today’s fisheries size limit of 63 mm, suggesting the possibility of a culturally prescribed set of harvesting size restrictions as well as preferences for particular Clam sizes.

The larger clams that characterized Kanish and Waiatt Bays beaches throughout much of the Late Holocene declined in numbers sometime in the Early Historic Period, which was instead characterized by slower-growing, smaller Clams. Toniello et al. attribute this decline in Clam productivity to the disease-related decimation of Indigenous human populations beginning 1782 AD and the consequent reduction in management of Clam gardens. Since fewer Clams were being harvested at this time, more nonharvested Clams died in situ of natural mortality and formed intertidal death assemblages. While there must have initially been some positive legacy effect on Clam growth from the engineered intertidal slope and years of cultivation, Toniello et al. suggest that eventually Clam habitats degraded as a result of the breakdown in the traditional Clam management practices that had been part and parcel of daily Human–Clam interactions for millennia.

Toniello et al.'s analyses of the Clams currently living in the now-defunct Clam garden beach suggest that growing conditions for Clams continued to worsen in the last century. It is striking that the growth patterns of Clams living in the beach today are most similar to the Clams that lived and died in the unstable and relatively unproductive habitats of the Early Holocene. As in the Early Historic Period, Toniello et al. propose that the current low productivity is due to the decline in traditional management, including ongoing tilling through harvesting. However, given the importance of substrate on Clam growth, Toniello et al. also attribute this recent pattern to the logging-induced deposition of silts on the Clam beaches, possibly compounded by recent changes in ocean temperatures and productivity. These fine sediments created a substrate less conducive to Clam growth than the coarse-grained substrates of the Clam gardens and early-Late Holocene nonwalled beaches. Ironically, the shallow slope of the Clam garden beaches and the lip of the Clam garden wall itself, initially created to enhance Clam production, now act as a sediment trap for logging silts in some Clam gardens.

Toniello et al.'s understanding of the historical ecology of Humans and Butter Clams on Quadra Island not only illustrates the long-term and intertwined relationships of these two species but also, serves as a model for studying the intricacies of other Human–species relationships. In the case of Butter Clams, a culturally valued species, there was a myriad of ecological and cultural factors that influenced population viability throughout the Holocene.  Toniello et al. expect similarly complex interactions among Humans and other species through time—whether through direct and deliberate interaction or through more indirect processes. Such complex Human–Clam interactions highlight the value of deeper-time baselines for informing modern fisheries management. 

On the Northwest Coast of North America, as in coastal communities worldwide, the Human–Clam relationship is age old and continues today. Tracing that history and situating these relationships in the context of modern management decisions take bringing together data from multiple sources and using diverse types of analyses. They also require recognizing the sometimes-active role of Humans in modifying coastal ecosystems of the past as well as the present and that not all long-term Human–ecological interactions have negative ecological consequences on biological diversity.

In Toniello et al.'s study area, their analyses of shells from intertidal death assemblages, archaeological shell middens, and modern Clams provide insights into how Clams, Clam habitats, and Human–Clam relationships changed through time in a specific place. More specifically, the analyses reveal how Clam life histories have responded to shifts in harvesting, habitat alterations, climate and environmental factors, and management practices. Taken together, the temporal and spatial variability that we document is another reminder of the need to gather site- and time-specific baselines for modern management. Toniello et al. have demonstrated that ocean temperatures and substrate play a role in Butter Clam life history. Thus, it is no surprise that there is considerable variation in estimates of Butter Clam size in the literature, just as there are in our modern data and paleodata. Management plans based on local, modern, and palaeoecological data are likely to be more robust than those based on more general spatiotemporal data from the literature. However, under future climate change scenarios, environmental variables are likely to resort in different combinations than those of recent history and perhaps, with few analogs in the past.

Previous research on Clam gardens in our study area demonstrated that Clam gardens today are at least twice as productive as nonwalled beaches. This has implications for the numbers of people who can be locally supported by this ancient innovation in mariculture. Toniello et al.'s data, however, show that Clams in Clam gardens today are far less productive than they were before European contact and industrial logging—that is, when traditional management systems were active and shell–sand–gravel vs. silt-rich beaches dominated clam habitats. This highlights the possibility that, if traditional mariculture methods were applied to Clam beaches today, they could produce even greater yields than those estimated based on current ecological conditions, assuming similar pelagic production and oceanic conditions. In fact, many Indigenous communities along the Pacific Northwest Coast are exercising their rights to access and collective choice by restoring Clam gardens and the traditional protocols associated with them.

Many coastal First Nations with whom Toniello et al. work observe that today’s Clam beaches are less productive, because they are no longer managed in traditional ways. In recognition of widespread marine environment degradation and the loss of coastal resources, local communities worldwide have spearheaded efforts to manage, restore, and conserve coastal resources and improve biodiversity and food security.

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