Per Solemdal (1941–2016) – an unconventional marine scientist

Per Solemdal (Figure 1) passed away on 4 April 2016 at the age of 75. He leaves behind a daughter and two sons, and two grandsons.

Figure 1. Per Solemdal at his summer residence located on Huglo island, south of Bergen in 1990, i.e. when he was 49. Photo: Victor Øiestad.

Per worked as a scientist at the Institute of Marine Research (IMR) in Bergen, Norway for his entire career, i.e. from the time he was appointed in 1967 to retiring in 2011, altogether for more than 43 years. Over the course of his career, he influenced two generations of fishery and marine biologists in Norway, both as a supervisor and as a colleague. Because of his deep appreciation of the history of marine science he would remind his students to always look at the original source because, as he used to state with great authority, but with a smile: ‘If you think you have a new idea, it is because you have not read the literature well enough’. He loved good, open academic discussions, and often approached scientific problems with a different and unexpected point of view. His extrovert personality often placed him in the centre of gatherings, both scientific and social.

Per was not a mainstream marine scientist. Despite writing many influential scientific papers, he was not really concerned with publishing on ‘silk paper’, as he put it. He had a broad interest in marine science, but focused on fish reproductive ecology and links to recruitment dynamics. His research interests followed an almost circular path; his studies into ‘maternal effects’ early in his career (1967–74), were picked up again from 1990 to 2011, when he came at it with much more knowledge and, not least, new ideas to present. Between these two periods, he made some notable contributions on early life stages of fish. Below we recollect these periods in his working life, and also include some of the other issues that captured this enthusiastic researcher’s interest.

1967–74

During the early years of his career, Per investigated how the eggs from flatfish populations, European flounder Platichthys flesus (Linnaeus, 1758) and European plaice Pleuronectes platessa (Linnaeus, 1758), evolve different physical and biological traits such as size, eggshell (chorion) thickness and ability to float (buoyancy) (Solemdal 1967; Lönning & Solemdal 1972; Solemdal 1973) under different environmental conditions. This work was innovative, as specimens from different ambient salinities in the Baltic Sea were transported to the laboratory in Bergen to determine local adaptations versus phenotypic plasticity. He concluded that ‘the specific gravity of the eggs is a fixed population characteristic which is almost unchangeable’ (Solemdal 1973). This issue of spatially, and possibly genetically, separated populations is central to the current concept of metapopulations and whether fisheries management, and thereby quotas, should be detailed to the level of sub-stocks.

1975–1989

From the mid 1970s, Per established an interdisciplinary science group to address the challenge of the recruitment dynamics of Arcto-Norwegian (Northeast Arctic (NEA)) cod Gadus morhua (Linnaeus, 1758), the largest Atlantic cod stock. The focal point of the project was the early larval stages, a time window that Johan Hjort (Hjort 1914) had hypothesized was crucial for offspring survival and year-class formation. The scientific approach integrated a diverse set of tools, including laboratory and field studies (including bioassays), as well as introductory individual-based modelling (Ellertsen et al. 1978, 1980). Per, however was particularly interested in in situ processes; he designed sampling equipment to show the vertical distribution of the fish eggs and larvae, and the naupliar food items for the larvae. This comprised a system of different pumps that enabled him to observe the precise position of the relatively sparse cod larval stages in relation to the more concentrated food. The largest pump had an impressive capacity of 1 m³ s⁻¹ (Ellertsen & Solemdal 1984). As a result, they were able to match the different biotic variables directly with the physical vertical variation (Ellertsen et al. 1984). The project continued until the end of the 1980s, by which time a series of spawning seasons and larval food abundances had been established. It was documented that high temperature is required for strong year classes of NEA cod to form, and that a possible mechanism is that temperature is linked to the timing of production of the larvae and their prey (Ellertsen et al. 1989), as hypothesized by Hjort (1914). However, the results of the project also pointed to a number of other biotic and physical drivers (Ellertsen et al. 1995). This brought Per to the next chapter of his research.

1990–2011

In 1990 he started revisiting the ‘maternal effects’ he had studied as a junior scientist, but this time he focused on ‘egg quality’, specifically egg malformations, in NEA cod as a function of spawning history (Figure 2). He was especially interested in comparing this in recruit and repeat spawners, as intense fishing leads to truncated age distributions and, relatively speaking, an increase in the number of recruit spawners and a decrease in the number of repeat spawners in the adult population. The general hypothesis was that repeat spawners are reproductively superior as they release more eggs per unit body weight and also bigger and ‘better’ eggs. Although this was broadly supported by the ‘IMR Lab. 3 – Bergen Marine Fish Reproduction Group’, which he was a most active member of at that time (Kjesbu et al. 1996; Solemdal 1997a; Marshall et al. 1998), the findings are still disputed, at least regarding egg quality, as this is an extremely challenging topic to address experimentally. Nevertheless, at that time ‘maternal effects’ were a really hot topic (and still are to some extent), because of the collapse of the Northern (Newfoundland) cod, which was historically of comparable stock size to the NEA cod, i.e. was the collapse due to overfishing or poor environmental conditions, or a combination of these? Per attended an international conference of the American Fisheries Society (AFS) in Eastern Canada in 1994 where these topics were discussed (Trippel et al. 1997). The experimental design he and his colleagues at IMR used was unique, in that naturally spawning pairs were individually tracked over seasons in 10 separate 20 m³ compartments of the so-called ‘Circular tank’ (Kjesbu et al. 1996; Solemdal et al. 1998). This enabled individual females to be examined both as recruit and repeat spawners under identical conditions. The results showed higher egg malformations and consequently higher egg mortality in recruit spawners, which was in line with field observations in the Vesterålen-Lofoten area, the main spawning ground of NEA cod (Korsbrekke et al. 2008). It is worth mentioning Per’s close cooperation over many years, both in the field and laboratory, with Dr Valeri Makhotin from Lomonosov Moscow State University. There were no limits as to how much effort these two colleagues and friends put into the study of egg malformation during the spawning season of NEA cod (Makhotin et al. 2001); day and night they could be found in the cool room examining samples or looking at specific egg characteristics under the microscope. Twenty-five years after Per started his pioneering work, the egg buoyancy work was put into a conceptual framework (Kjesbu et al. 1992), and the underlying physiological processes detailed shortly thereafter indicated that Per was correct in his deduction that buoyancy is a ‘fixed characteristic’ for a stock, pre-determined during oogenesis (Thorsen et al. 1996). The extensive time series and experimental data that Per and his colleagues collected still attracts interest and new research questions, e.g. in Höffle et al. (2014) on the distribution of spawning cod in Lofoten, the last article with Per as a co-author.

Figure 2. Example of a healthy (A) and malformed (B) NEA cod egg as Per Solemdal and Valeri Makhotin could see them under the stereo microscope, typically using the IMR research vessel Johan Hjort (C) as a working platform in the Lofoten area. The eggs showed a range of developmental stages, presently containing advanced larvae. Photos: A: Anders Thorsen, IMR; B: Valeri Makhotin, Lomonosov Moscow State University; C: Silje Elisabeth Seim, IMR.

Additional activities

Throughout his career, with his vast knowledge of early life stages in wild populations, Per contributed to the work of many fish biologists to make species such as the Atlantic halibut Hippoglossus hippoglossus (Linnaeus, 1758) a new species in marine aquaculture (Solemdal et al. 1974; Haug et al. 1984).

Per published an article with Michael Sinclair, former director of the Bedford Institute of Oceanography, Canada, about the first IMR director, Johan Hjort: the man, his crew and his science (Sinclair & Solemdal 1988). Per also wrote a play about Johan Hjort and three of his ‘cavaliers’, Knut Dahl, Bjørn Helland-Hansen and Désiré Damas, which was performed at the above-mentioned 1994 AFS Larval Fish Conference (Solemdal 1997b). His interest in information dissemination also influenced the weekly lecture seminar series at IMR, ‘Ukens Orientering’, which he led for a number of years. He always introduced the presenters with a poem or a story. When Vera Schwach published the history of IMR for its 100-year anniversary in 2000 (Schwach 2000), Per provided her with many anecdotes about Johan Hjort.

Postscript

We believe that Per Solemdal’s intellectual influence and legacy is hugely underestimated by any bibliometrics such as the h-index or the number of peer-reviewed articles that are commonly used to measure researchers’ performance. Rather than working for personal merit Per was far more concerned about bringing out the best in others. Two generations of Norwegian marine scientists, particularly at IMR, benefited from his teaching and mentoring, and remember to ‘look to the past’ when working on current issues and problems. He was also influential in making it acceptable to combine laboratory experiments with challenging issues in the field, many of which still remain to be solved, especially related to climate change. Most importantly, Per Solemdal’s interesting perspectives and input will be missed, but his spirit will remain in our marine science community.

Acknowledgements

We would like to thank Håkon Otterå, IMR and Lisa Maddison, IMBER for commenting upon an earlier version of this obituary.